Reply
 
Thread Tools Display Modes
 
Old 04-05-2017, 01:24 AM   #1
Platinum Member
 
Join Date: Mar 2017
Location: Nebraska
Posts: 103
Default Isolator, Coach Batteries Issues

This may be a long story, but here goes. I am a fairly new Class B owner. The other night, the Check Gauges light went on and the alternator gauge on my 2002 Dodge Ram Van 3500 Leisure Travel went all the way to the left. I turned off all electricity and made it to the nearest campground. The next morning AAA assisted me to a reputable car clinic. According to them my alternator was putting out 27 volts, frying my engine battery. So, I had them replace both. It tested OK for them in the shop. But in test driving the rig, the Check Gauges light came back on and they said the voltage dropped to 8 volts. I suppose they had a computer hooked to the diagnostic port. They had no knowledge of motorhomes and saw that the wiring went through the isolator. Hence, the disconnected the cables to it and tied the alternator and engine battery cables together. Problem solved in their minds.

Being a new owner of the van, I suspected that maybe the coach batteries were weak, so I asked them to load test them. They left them hooked together during testing. One tested bad and one tested good. What is surprising to me is that the "Charge Eye" on the bad one showed "Green" or Good and the "Charge Eye" on the good one showed "Red" or bad! Consequently, I began to wonder if the bad battery developed a short, making the alternator put out too much voltage, burning it out and also the engine battery. And, could a malfunctioning isolator be the cause of this? And why only 8 volt output of the alternator when the isolator and coach batteries were hooked up?

In doing studying, I found in the documentation that accompanied the coach, a sheet pertaining to the isolator in the van. It included a procedure for checking the isolator, using a voltmeter to determine if it stops current one direction and lets it pass the other direction. I only have on hand a very inexpensive voltmeter, but I conducted the test. Going from the alternator post to ground there is some resistance, but some openness. Going from the alternator to the engine battery post (I think), there is resistance one direction and openness the other direction. But going from the alternator post to the coach batteries post, there is no openness for either polarity. Again, this is an inexpensive, needle version of a voltmeter.

I am now on the road, but stranded with brake problems (not related, of course), but I have struggled to find someone familiar with motorhome wiring. They all say they know nothing about them, although I feel the situation may be fairly simple for some knowledgeable person. So, I am turning to this forum. I hope some of may off me some comments and advice.

Any thoughts! Thanks in advance!
Gregg
__________________

gksmith is offline   Reply With Quote
Old 04-05-2017, 01:42 AM   #2
BBQ
Platinum Member
 
Join Date: May 2016
Location: East
Posts: 2,484
Default

.

How old are your house batteries?
__________________

BBQ is offline   Reply With Quote
Old 04-05-2017, 03:34 PM   #3
Platinum Member
 
Join Date: Mar 2017
Location: Nebraska
Posts: 103
Default

I do not know. I bought the unit last November, but I am quite sure the dealer did not put new ones in. So they are probably up for replacement. I think replacement will be my first step unless I get advised differently. If one battery is good and the other bad, I could use the good one in a pop-up camper I have. But I am also concerned about the isolator--can it cause problems?
gksmith is offline   Reply With Quote
Old 04-05-2017, 04:19 PM   #4
BBQ
Platinum Member
 
Join Date: May 2016
Location: East
Posts: 2,484
Default

.

I doubt the dealer would be so benevolent as to give you a new battery.
They will get away with murder if they can,
which I think they just got away with murder.

There should be a date code on the battery.

If the batteries do not look new,
they are not new.
ie. you should replace them.
They are good for approx 5 yrs.
Some have luck in keeping them longer.
But if they have ever been discharged below 50% for an extended period of time, they are weakened, or maybe even toasted.

Which isolator do you have? Brand? model number?
Picture?
BBQ is offline   Reply With Quote
Old 04-05-2017, 06:31 PM   #5
Platinum Member
 
Join Date: Mar 2017
Location: Nebraska
Posts: 103
Default

I cannot find a manufacturing date, but the batteries are fairly dirty. I am sure they have some age on them, but I have no idea how much. Plus I have no idea how they were treated. I do know that they would at least handle my needs for overnight, but I always either drove the next day or would be on shore power, hence they were never tested for a long period.

The isolator is manufactured by Leisure Components. Model 496HT, 3 post, 135 Amp. Link to picture: [URL="http://https://1drv.ms/i/s!AtjihSWJj8H2gq02vCdjuT6ho0Spdg"]

Can a bad isolator do damage to anything other than not protecting the engine battery?

Do batteries have to be detached from each other when doing voltage testing?

Thanks for the replies. They are very much appreciated!
gksmith is offline   Reply With Quote
Old 04-05-2017, 07:45 PM   #6
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 8,031
Default

Isolators can cause some damage from what I have heard. It appears some of them sense the voltage of one or the battery banks, and if that connection is lost the alternator can lose reference and go full voltage, which may be what happened initially to you.

Batteries that are in parallel have to be disconnected to get any useful voltage readings. In series you can check then connected, but it is still best to disconnect them and let them sit a while before checking.

You may want to just consider biting the bullet and replacing the whole works on the coach side. Two new TRUE DEEP CYCLE batteries, and a new isolator or upgrade to a solid state separator/combiner
booster is offline   Reply With Quote
Old 04-05-2017, 08:02 PM   #7
Platinum Member
 
Join Date: Mar 2017
Location: Nebraska
Posts: 103
Default

Thanks for the additional input and information.

Do you have a recommendation for the upgrade solid state separator/combiner? I found one at Robust, inexpensive 12V 150+amp smart battery isolator and smart split charge relay for RV, car, and truck applications, dual battery isolator but I was surprised how little it cost and how small it seemed. My current isolator seems much more robust, but perhaps that is due to different technology.
gksmith is offline   Reply With Quote
Old 04-05-2017, 09:36 PM   #8
BBQ
Platinum Member
 
Join Date: May 2016
Location: East
Posts: 2,484
Default

Battery Doc 12 Volt 150 Amp Battery Isolator - Wirthco Engineering, Inc.

BBQ is offline   Reply With Quote
Old 04-05-2017, 11:25 PM   #9
Platinum Member
 
Join Date: Nov 2015
Location: CA
Posts: 1,612
Default

Quote:
Originally Posted by booster View Post
Isolators can cause some damage from what I have heard. It appears some of them sense the voltage of one or the battery banks, and if that connection is lost the alternator can lose reference and go full voltage, which may be what happened initially to you.
I'm not aware of any isolators that employ a battery voltage sensor. The sensing terminal typically was on the alternator which examined battery voltage and adjusted the alternator voltage to compensate for voltage drop across the isolator diodes + cable resistance losses.

I think hard wired alternator sensing technology has been replaced with the advent of computer control of alternator field windings which makes the report of 27 volts delivered a little puzzling because the computer is continuously monitoring battery(s) terminal voltage and if it sees no battery voltage, it clamps the alternator field current to prevent the alternator from taking off into over voltage. To deliver 27 volts from the alternator, the field windings would have to be subjected to a forced full field condition which seems unlikely if there is a physical connection to any battery.

Additionally, every appliance in the coach would be subjected to 27 volts and I am puzzled why there was't some appliance and lighting filament failures.
cruising7388 is offline   Reply With Quote
Old 04-05-2017, 11:34 PM   #10
Platinum Member
 
Join Date: Nov 2015
Location: CA
Posts: 1,612
Default

Quote:
Originally Posted by gksmith View Post
Thanks for the additional input and information.

Do you have a recommendation for the upgrade solid state separator/combiner? I found one at Robust, inexpensive 12V 150+amp smart battery isolator and smart split charge relay for RV, car, and truck applications, dual battery isolator but I was surprised how little it cost and how small it seemed. My current isolator seems much more robust, but perhaps that is due to different technology.
When employing isolators and the alternator is turning, both engine and house batteries are charged but when shore power is hooked up, the battery charger typically will only charge the house battery. A bi-directional separator addresses this and will permit the shore power battery charger to address both batteries.

A commonly found separator for this is the Surepower 1315 bi-directional separator which is offered in both 100 and 200 watt versions. The Cadillac quality separators are ACR separators made by Blue Sea.
cruising7388 is offline   Reply With Quote
Old 04-06-2017, 01:02 AM   #11
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 8,031
Default

[QUOTE=cruising7388;55695]I'm not aware of any isolators that employ a battery voltage sensor. The sensing terminal typically was on the alternator which examined battery voltage and adjusted the alternator voltage to compensate for voltage drop across the isolator diodes + cable resistance losses.

I think hard wired alternator sensing technology has been replaced with the advent of computer control of alternator field windings which makes the report of 27 volts delivered a little puzzling because the computer is continuously monitoring battery(s) terminal voltage and if it sees no battery voltage, it clamps the alternator field current to prevent the alternator from taking off into over voltage. To deliver 27 volts from the alternator, the field windings would have to be subjected to a forced full field condition which seems unlikely if there is a physical connection to any battery.

Additionally, every appliance in the coach would be subjected to 27 volts and I am puzzled why there was't some appliance and lighting.

If the battery reference gets lost the alternator will go high. This pix gets reference through the isolator, others do it with a separate wire, and I would think either could fail.





An alternator without a battery reference will normally go high, from all I have heard.

I would stay away from the basically obsolete design of the Surepower separator. They are coil relay type, and fail fairly often, but worst of all the eat about 1.5 amps whenever activated. Some of the numbers I have seen for the solid state ones are in the tenths of a volt, some of the Blue Sea are zero. I would not put a another isolator in either, as it is kind of a waste and it will reduce the charging voltage to the coach compared to a separator.
booster is offline   Reply With Quote
Old 04-06-2017, 01:45 AM   #12
Platinum Member
 
Join Date: Nov 2015
Location: CA
Posts: 1,612
Default

[QUOTE=booster;55701]
Quote:
Originally Posted by cruising7388 View Post
I'm not aware of any isolators that employ a battery voltage sensor. The sensing terminal typically was on the alternator which examined battery voltage and adjusted the alternator voltage to compensate for voltage drop across the isolator diodes + cable resistance losses.

I think hard wired alternator sensing technology has been replaced with the advent of computer control of alternator field windings which makes the report of 27 volts delivered a little puzzling because the computer is continuously monitoring battery(s) terminal voltage and if it sees no battery voltage, it clamps the alternator field current to prevent the alternator from taking off into over voltage. To deliver 27 volts from the alternator, the field windings would have to be subjected to a forced full field condition which seems unlikely if there is a physical connection to any battery.

Additionally, every appliance in the coach would be subjected to 27 volts and I am puzzled why there was't some appliance and lighting.

If the battery reference gets lost the alternator will go high. This pix gets reference through the isolator, others do it with a separate wire, and I would think either could fail.





An alternator without a battery reference will normally go high, from all I have heard.

I would stay away from the basically obsolete design of the Surepower separator. They are coil relay type, and fail fairly often, but worst of all the eat about 1.5 amps whenever activated. Some of the numbers I have seen for the solid state ones are in the tenths of a volt, some of the Blue Sea are zero. I would not put a another isolator in either, as it is kind of a waste and it will reduce the charging voltage to the coach compared to a separator.
Correct me if I'm wrong, but it appears to me that the pix doesn't show battery sensing from the isolator. Why would a sensing circuit require a 6 amp breaker? Isn't the E terminal on the isolator used to ensure initial excitation to the alternator and isn't battery sensing and alternator field current provided at alternator terminals A and I?
cruising7388 is offline   Reply With Quote
Old 04-06-2017, 02:54 PM   #13
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 8,031
Default

[QUOTE=cruising7388;55702]
Quote:
Originally Posted by booster View Post

Correct me if I'm wrong, but it appears to me that the pix doesn't show battery sensing from the isolator. Why would a sensing circuit require a 6 amp breaker? Isn't the E terminal on the isolator used to ensure initial excitation to the alternator and isn't battery sensing and alternator field current provided at alternator terminals A and I?
The 6 amp circuit in that diagram is just a tie in some use to have it activate off the ignition and not the point.

What is a concern is that the battery is on 1 and the alternator on A, through the isolator, which means the alternator is not seeing true battery voltage. If the voltage drop there increases, the alternator voltage increases, and anything that is wired to the alternator will see higher voltage. This is with a single wire alternator. If it was an alternator with a voltage sense input, and internal regulator, there would be a wire from the battery to the sense input on the alternator. If that wire were to be broken, the alternator would stay connected to everything, and the alternator would go to full output, I think.
booster is offline   Reply With Quote
Old 04-06-2017, 06:23 PM   #14
Platinum Member
 
Join Date: Mar 2017
Location: Nebraska
Posts: 103
Default

The thread is getting a little more complicated than I can comprehend, but I certainly appreciate the responses. Consequently, I now have the following questions:

1) Is it or is it not the consensus that a faulty isolator can cause alternator problems? Or was it other factors that probably caused my initial problem?

2) Is an Automatic Charging Relay the same as a battery separator? It was stated that Blue Sea is the Cadillac of such products. I am looking at https://www.amazon.com/gp/product/B0...=AG2F8PI91T85K. Is this what I need? Can I use this to replace the current isolator without any additional wiring or fusing? It seems that several posts suggested adding a fuse in the line. I want it as simple as possible, but properly done.

3) I am on the road, but staying for a short time at my daughter in Tennessee. I cannot find an RV place willing to look at my situation. If I merely replace my coach batteries (consequently replacing the one that tested bad), but not the isolator, will I create other problems? It seems that ordering a product takes over a week for delivery and I need to keep moving.

Thanks again!
gksmith is offline   Reply With Quote
Old 04-06-2017, 06:53 PM   #15
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 8,031
Default

My opinion yes an isolator can cause alternator problems, but on your year, it was probably more likely a bad connection on the battery to alternator sensing wire, as you probably don't have a single wire alternator. If that was the case, it is probably the isolator got fried from the high voltage, which may have been good and saved other electronics.

On the ACR, yes the same as separator. I hate when the Amazon sellers show all kinds of different models but don't list what model number actually is. Many look the same, but are different. That said, if the pic is correct, it is probably my second favorite ACR, model 7620. Favorite is the 7622 which is identical except for an manual overide knob to lock out for servicing systems. I have seen 7620s for $150ish and 7622s for $190ish. Search by model number on Google. The remote switch is an excellent feature to have for lots of reasons, and is on both models, and you dash mount it.

IIRC, you they have already bypassed the isolator for the engine battery, but you didn't mention if the also tied in the coach batteries directly to the alternator and starting battery. If they didn't, they will not be charging if the isolator is disconnected, while you drive.

Before you buy any batteries, I think you would benefit from having them disconnected from the van and each other, and charged up separately, then tested, to see what you are dealing with. Replacing one battery of an older pair is usually not a good idea due to mismatching. If you have wet cells, and one looks weaker, a battery shop should be able to try to equalize it, to see if it will come back, as the often will.
booster is offline   Reply With Quote
Old 04-06-2017, 08:59 PM   #16
Platinum Member
 
Join Date: Nov 2015
Location: CA
Posts: 1,612
Default

[QUOTE=booster;55708]
Quote:
Originally Posted by cruising7388 View Post

The 6 amp circuit in that diagram is just a tie in some use to have it activate off the ignition and not the point.

What is a concern is that the battery is on 1 and the alternator on A, through the isolator, which means the alternator is not seeing true battery voltage. If the voltage drop there increases, the alternator voltage increases, and anything that is wired to the alternator will see higher voltage. This is with a single wire alternator. If it was an alternator with a voltage sense input, and internal regulator, there would be a wire from the battery to the sense input on the alternator. If that wire were to be broken, the alternator would stay connected to everything, and the alternator would go to full output, I think.
You provided a diagram to support an example of an isolator array that incorporates a sensing "E" terminal. It doesn't. The 6 amp circuit in that diagram is provided for internally regulated alternators that require external excitation to get lift off. It has nothing to do with battery sensing which is accomplished at the alternator, not the isolator.

No question that the loss of battery sensing could prompt an alternator to go into full squash but whether that actually occurs depends on how the alternator is regulated. In the diagram you cite, with a loss of battery voltage sense, the alternator voltage will soar and the diode(s) may or may not survive the potential for a spike upon disconnect. But gksmith's coach is a 2002 Dodge with an OBD II computer that controls alternator field current and it is the computer and not the alternator that monitors battery voltage. If an open develops between the alternator and the battery, the computer recognizes the open circuit and clamps the alternator field winding current to a safe level sufficiently fast to protect the alternator and equally important, the loads it feeds. Actually, Dodge implemented this system as early as 1990 in their OBD 1 computers. This is why I have some doubts regarding the 27 volts reported being delivered from the alternator unless the computer is malfunctioning.
cruising7388 is offline   Reply With Quote
Old 04-06-2017, 09:23 PM   #17
Platinum Member
 
Join Date: Mar 2017
Location: Nebraska
Posts: 103
Default

I certainly appreciate all of the input all of you have given me. Now for the next questions. As I stated, I am on the road, but staying short term at my daughter until I get things straightened out. So I do not have at hand everything desirable--eg. tools, time, knowledge of the area, etc. and consequently I am trying to get by safely.

1) Booster, you are correct, the isolator is bypassed and the coach batteries are not currently connected to the alternator. So, my question is, would it be OK to connect the coach battery cable to the alternator and engine battery cables? I understand I run the risk of not having starting power if the batteries ran down, but I drive every day and I do not believe we really do use much battery power at night when we boondock. One concern would be that of having the deep cycle batteries connected to the starter and also that of the batteries attempting to equalize. What do you think?

2) Everybody I contact say they are too busy to help with my electrical problems and/or when they see a motorhome, they say they do not have the knowledge. So I have to proceed on my own. Will not having the coach plugged into shore power give me the charge I need? And if I separate the batteries, I could charge each individually this way to test. I plan on purchasing a hygrometer to test the cells and a digital voltmeter to determine the voltage of each. It seems like I should have this equipment anyway to properly maintain the batteries. Any comments?

3) I have read that one should not discharge deep cycle batteries less than 50%. But, how does one determine this? Do some coaches have voltmeters? I only have LEDs that show thirds--full, 2/3, 1/3, and empty. Is this the equivalent? And how can I determine the accuracy of the LEDs?

I respect everyone's knowledge and willingness to help!
Gregg
gksmith is offline   Reply With Quote
Old 04-06-2017, 09:45 PM   #18
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 8,031
Default

[QUOTE=cruising7388;55719]
Quote:
Originally Posted by booster View Post

You provided a diagram to support an example of an isolator array that incorporates a sensing "E" terminal. It doesn't. The 6 amp circuit in that diagram is provided for internally regulated alternators that require external excitation to get lift off. It has nothing to do with battery sensing which is accomplished at the alternator, not the isolator.

No question that the loss of battery sensing could prompt an alternator to go into full squash but whether that actually occurs depends on how the alternator is regulated. In the diagram you cite, with a loss of battery voltage sense, the alternator voltage will soar and the diode(s) may or may not survive the potential for a spike upon disconnect. But gksmith's coach is a 2002 Dodge with an OBD II computer that controls alternator field current and it is the computer and not the alternator that monitors battery voltage. If an open develops between the alternator and the battery, the computer recognizes the open circuit and clamps the alternator field winding current to a safe level sufficiently fast to protect the alternator and equally important, the loads it feeds. Actually, Dodge implemented this system as early as 1990 in their OBD 1 computers. This is why I have some doubts regarding the 27 volts reported being delivered from the alternator unless the computer is malfunctioning.
I would think the RV isolator wiring could mess up some of the safety stuff concerning opens, but the low voltage results after the first issue may indicate they are now activated.

The PCM regulators are really like most other remote regulators, only with some other inputs to compensate for load changes like rear defoggers. I found this on a Dodge site for a 2004, I think.




It would seem to indicate two field wires with one full time 12v and the other regulating the current via variable voltage to ground at the pcm. The third wire would be a confirmation of engine on, so the alternator doesn't start too hard, probably, or maybe to prevent vampire drain. It could also be the voltage sense to the pcm.

I would think any of the problems mentioned with internal or other external regulators could also happen. I did find it interesting on that site that they said there are tons of the Dodges running around with the pcm control failed and disconnected, with the alternator connected to the previous generation fenderwell mount remote standalone regulator. Must be a common failure in the pcm. The also mentioned many replacement alternators not working correctly when installed.

With the OP not able to troubleshoot himself, and apparently very hard to find help, he is in a bind if his voltages are bouncing around a lot.

Probably the most certain would be to do a remote reg conversion, but that is likely above his pay grade, and he can't find any help at this point. A Dodge dealer may be able to help, but will likely want to remove the isolator, disconnect the coach and take it back stock, with expensive parts.

Tough call as to where to go next.
Attached Images
File Type: jpg dodge alternator reg.jpg (49.4 KB, 68 views)
booster is offline   Reply With Quote
Old 04-06-2017, 09:59 PM   #19
Platinum Member
 
Join Date: Aug 2010
Location: Minnesota
Posts: 8,031
Default

Quote:
Originally Posted by gksmith View Post
I certainly appreciate all of the input all of you have given me. Now for the next questions. As I stated, I am on the road, but staying short term at my daughter until I get things straightened out. So I do not have at hand everything desirable--eg. tools, time, knowledge of the area, etc. and consequently I am trying to get by safely.

1) Booster, you are correct, the isolator is bypassed and the coach batteries are not currently connected to the alternator. So, my question is, would it be OK to connect the coach battery cable to the alternator and engine battery cables? I understand I run the risk of not having starting power if the batteries ran down, but I drive every day and I do not believe we really do use much battery power at night when we boondock. One concern would be that of having the deep cycle batteries connected to the starter and also that of the batteries attempting to equalize. What do you think?

2) Everybody I contact say they are too busy to help with my electrical problems and/or when they see a motorhome, they say they do not have the knowledge. So I have to proceed on my own. Will not having the coach plugged into shore power give me the charge I need? And if I separate the batteries, I could charge each individually this way to test. I plan on purchasing a hygrometer to test the cells and a digital voltmeter to determine the voltage of each. It seems like I should have this equipment anyway to properly maintain the batteries. Any comments?

3) I have read that one should not discharge deep cycle batteries less than 50%. But, how does one determine this? Do some coaches have voltmeters? I only have LEDs that show thirds--full, 2/3, 1/3, and empty. Is this the equivalent? And how can I determine the accuracy of the LEDs?

I respect everyone's knowledge and willingness to help!
Gregg
You are wise to worry about the coach batteries overloading things if connected full time to the starting battery. The wiring may be very small, but should be breaker protected, so it shouldn't be a flaming mess, but not good. You could get a small jumper to temporarily connect them together if you needed and emergency charge, if you have no other source.

Those two items will tell you a lot. Voltage for the system functions and hydrometer for battery state of charge ( I like the EZred model personally)

Don't use the lights to determine state of charge, they are very inaccurate. Use the hydrometer for very accurate, voltmeter for close. There is growing evidence that the 50% rule is mostly legend and very little fact. The numbers we have seen would indicate a loss of total amp hours of use between 50% or down to 20% down is somewhere slightly above 10% difference, so not the disaster we hear all the time.

If you can do it, not having coach charging while driving will be your easiest way, as long as the voltage is OK on the engine battery charging. Shore power would be needed regularly though, based on your power needes.

You might let everyone know where you are, as maybe someone is nearby that could help out. It is a very helpful and knowledgeable bunch on here.
booster is offline   Reply With Quote
Old 04-07-2017, 12:28 AM   #20
Platinum Member
 
Join Date: Nov 2015
Location: CA
Posts: 1,612
Default

[QUOTE=booster;55725]
Quote:
Originally Posted by cruising7388 View Post

I would think the RV isolator wiring could mess up some of the safety stuff concerning opens, but the low voltage results after the first issue may indicate they are now activated.

The PCM regulators are really like most other remote regulators, only with some other inputs to compensate for load changes like rear defoggers. I found this on a Dodge site for a 2004, I think.




It would seem to indicate two field wires with one full time 12v and the other regulating the current via variable voltage to ground at the pcm. The third wire would be a confirmation of engine on, so the alternator doesn't start too hard, probably, or maybe to prevent vampire drain. It could also be the voltage sense to the pcm.

I would think any of the problems mentioned with internal or other external regulators could also happen. I did find it interesting on that site that they said there are tons of the Dodges running around with the pcm control failed and disconnected, with the alternator connected to the previous generation fenderwell mount remote standalone regulator. Must be a common failure in the pcm. The also mentioned many replacement alternators not working correctly when installed.

With the OP not able to troubleshoot himself, and apparently very hard to find help, he is in a bind if his voltages are bouncing around a lot.

Probably the most certain would be to do a remote reg conversion, but that is likely above his pay grade, and he can't find any help at this point. A Dodge dealer may be able to help, but will likely want to remove the isolator, disconnect the coach and take it back stock, with expensive parts.

Tough call as to where to go next.
The large black wire referred to isn't for providing engine confirmation, addressing hard starts, parasitics or voltage sensing. This is the alternator power output lead that connects from the B+ terminal on the alternator to the battery(s) or in this particular case, to the isolator. In a non -RV setup, as the writer indicates, this wire will always show voltage whether the alternator is spinning or at rest. But if diode isolators are employed, with the engine off, the diodes are reverse biased and there is no voltage on this lead when the alternator is at rest which is why there are diode models available with the "E" terminal to provide excitation to some alternator designs (e.g. Delco Delphi CS) that that requires external excitation for alternator lift off.

The writer reports that sometimes replacement alternators don't function properly. If they are not identical replacements, this link suggests the importance of choosing the correct alternator model:

http://www.allbatterysalesandservice..._Isolators.pdf


The field winding explanation is correct. One lead is assigned battery voltage. The other lead connects to a terminal on the computer. The level of alternator field current is controlled by the computer adjusting the ground return threshold and the net voltage is applied to the field winding and will typically vary from 4- 11 volts depending on the level of coach engine and house load demands on the alternator.

The writer cites anecdotal reports of computer failure to properly provide regulation and this probably has merit. The inputs and outputs to and from these computers is mostly at a low power signal level. But the amperage required for alternator field current is not milliamps but amps and and under high alternator output requirements, things might start getting a little toasty at the computer heatsink. Considering that replacing the computer will cost hundreds of dollars, spending a fraction of that to use an external regulator like the multi-stage Balmars, makes economic sense.

If I was the OP, I would buy an OBD II computer code reader. They've come down dramatically in price. Besides a digital voltmeter, IMO, they are a valuable and cost saving tool for narrowing down or at least ruling out what's causing the problem. If the alternator is actually putting out 27 volts, it's in full field and neither open nor shorted diodes nor defective batteries should produce this symptom with the computer controlled regulation his Dodge has. If the failure is at the computer, a code reader should throw a fault code.
__________________

cruising7388 is offline   Reply With Quote
Reply

Tags
coach batteries, isolator

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 04:56 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
×