2007 Chev charging intermittents

[roadbiker1]

That is the standard test for an isolator, but with the excitation wire, with breaker here, you have to get that also moved to the right place, which is probably to the alternator or it may not work. I have heard several times of people that switched to a charge relay and then the alternator quit working because of the excitation going to isolator they used to have didn't get moved.

got back from second little trip, van did ok, maybe one start w/ no charge but immediate restart brought back charging.
I like yr idea of the field current getting whacked on occasion, probs by a relay. Have been trying today at home base to get it to NOT CHARGE, but it stubbornly will not. When it next does not charge, I'll jump on the E terminal as you suggested, and if it is 0 volts, I'll jumper it over to one of the batts... as you may note, I not only have them in my belfry, there is at least one in the isolator.

Cheers, and thanks! If this works, name yr beer ;- )

j

forgot to include by graphic

 

[roadbiker1]

can't tell if my attached. jpg is making it across or no..

 

[peteco]

Perhaps you have a flaky circuit breaker (may have been suggested already).

 

[roadbiker1]

Still waiting the next. no charge event to investigate... but what I think is the alt's field current comes thru a little relay as well, so that is another potential problem. What I don't particularly understand is if the field winding needs an externally supplied current at all times, or only when starting up. Any comments on this? Thanks....

 

[booster]

Still waiting the next. no charge event to investigate... but what I think is the alt's field current comes thru a little relay as well, so that is another potential problem. What I don't particularly understand is if the field winding needs an externally supplied current at all times, or only when starting up. Any comments on this? Thanks....

As in most things, it all depends....

If you have conventional, internal regulated, alternator it would probably need an initiate signal from the key on or PCM and then it would run on it's own.

If it is a modern, PCM, controlled one, the field current is supplied or controlled by the PCM so it would need that full time. The current is also based on controlling output for accessories turn on, recover energy on coast, etc based on model.

On a Chevy it appears the change came in the 2007/2008 model change. Our 2007 can with an internal regulated alternator, but it appears the 2008s came with a PCM controlled alternator.

 

[roadbiker1]

As in most things, it all depends....

If you have conventional, internal regulated, alternator it would probably need an initiate signal from the key on or PCM and then it would run on it's own.

If it is a modern, PCM, controlled one, the field current is supplied or controlled by the PCM so it would need that full time. The current is also based on controlling output for accessories turn on, recover energy on coast, etc based on model.

On a Chevy it appears the change came in the 2007/2008 model change. Our 2007 can with an internal regulated alternator, but it appears the 2008s came with a PCM controlled alternator.

so if i have the internal regulator, I should have a voltage on the field line only at key on?
And then it goes internal for field current after start? Does this initiate current then go away
or times out somehow?

 

[roadbiker1]

I hung an LED on the "initiator" E terminal on the isolator... it comes on with key on, and then stays on, presumably b.c. the alt itself is now providing its own field current, and good for it.
what I'm not getting in my head, is how this initial field current gets to the alt.. my diagram only shows the 3 fat big current carriers + the line to the initiator E terminal that looks like it carries current from a little relay and a 10A breaker.
And as before, now that I'm watching closely, the alt is behaving ;- ). And as before, thanks
for your insights...

j

 

[booster]

so if i have the internal regulator, I should have a voltage on the field line only at key on?
And then it goes internal for field current after start? Does this initiate current then go away
or times out somehow?

I don't think you will see much field current from just key on with the engine not running as it is the initiate signal. Once the alternator starts to spin the regulator in the alt should start feeding power to the field.

I hung an LED on the "initiator" E terminal on the isolator... it comes on with key on, and then stays on, presumably b.c. the alt itself is now providing its own field current, and good for it.
what I'm not getting in my head, is how this initial field current gets to the alt.. my diagram only shows the 3 fat big current carriers + the line to the initiator E terminal that looks like it carries current from a little relay and a 10A breaker.
And as before, now that I'm watching closely, the alt is behaving ;- ). And as before, thanks
for your insights...

j

Our 07 with an internal regulator has a small 4 wire connector plugged into the rear of it but it carries only two wires. One wire is the initiate wire from the ignition and one is a feedback to the pcm that tells it field % load so the pcm can adjust engine parmaters to cover the loads. We here all the time about people removing the isolator and putting in a charge relay, only to find the alternator no longer works because you need to find the initiate original wire wherever they put it when the isolator went in and reconnect it to alternator connector. My guess is that the relay is doing that now, but I don't know for sure.

 

[roadbiker1]

got back from second little trip, van did ok, maybe one start w/ no charge but immediate restart brought back charging.
I like yr idea of the field current getting whacked on occasion, probs by a relay. Have been trying today at home base to get it to NOT CHARGE, but it stubbornly will not. When it next does not charge, I'll jump on the E terminal as you suggested, and if it is 0 volts, I'll jumper it over to one of the batts... as you may note, I not only have them in my belfry, there is at least one in the isolator.

Cheers, and thanks! If this works, name yr beer ;- )

j

still chasing my charging prob, but in true digital backwoods fashion, put an LED test light on the E terminal of the cursed red box , and, voila! the system has NOT F'd up thru maybe 10 engine start / stop cycles.
Maybe I have scared it? So far it always shows voltage on the E term, and the alt charges.

 

[roadbiker1]

I don't think you will see much field current from just key on with the engine not running as it is the initiate signal. Once the alternator starts to spin the regulator in the alt should start feeding power to the field.

Our 07 with an internal regulator has a small 4 wire connector plugged into the rear of it but it carries only two wires. One wire is the initiate wire from the ignition and one is a feedback to the pcm that tells it field % load so the pcm can adjust engine parmaters to cover the loads. We here all the time about people removing the isolator and putting in a charge relay, only to find the alternator no longer works because you need to find the initiate original wire wherever they put it when the isolator went in and reconnect it to alternator connector. My guess is that the relay is doing that now, but I don't know for sure.

so what does the E terminal do? It looks like it gets current from the batt thru a relay and breaker but
then what? I don't see it spitting out field current thru a connection to the alt.. have you taken one apart? Someone said theirs had a burn spot on theirs so they replaced it... would have liked to see what was inside besides BigAss diodes ;- )

Still waiting for my rig to NOT charge so I can poke it... a sure bet it will behave ;- ). Someone else
had a bad relay going to the E term... I like the idea, just need it to glitch out one more time when
I'm ready to catch it.,,

 

[booster]

so what does the E terminal do? It looks like it gets current from the batt thru a relay and breaker but
then what? I don't see it spitting out field current thru a connection to the alt.. have you taken one apart? Someone said theirs had a burn spot on theirs so they replaced it... would have liked to see what was inside besides BigAss diodes ;- )

Still waiting for my rig to NOT charge so I can poke it... a sure bet it will behave ;- ). Someone else
had a bad relay going to the E term... I like the idea, just need it to glitch out one more time when
I'm ready to catch it.,,

I have not ever had to deal with an isolator, so I consider myself lucky.

Normally there would be 3 or 4 wires on a 1 alternator 2 battery isolator. The would be starting battery, coach battery(s), alternator output, and if the fourth is the excitation or E.

E is the turn on signal for the isolator to turn on and work and would normally, AFAIK, come from any 12v switched source like the ignition run position. I 2007 a Chevy would have an internal regulated alternator so you must have a 2007 chassis as I believe all the 2008 Chevies have PCM controlled alternators with no internal regulator in the alternator.

My guess would be that the E wire is connected to the relay and battery because if yours is like ours the turn on signal for the alternator is 5v from the PCM so probably couldn't directly turn on the isolator. The relay would be either ignition controlled or a 5v coil relay using the PCM turn on. I ran in to this exact problem on our Wakespeed remote regulator for the standalone add on alternator. The Wakespeed would not turn of from the low voltage PCM turn on signal so I had to run an ignition switch line to it.

I would still just get rid of the isolator and rewire the alternator back to factory wiring. Then install a charge relay/separator relay type control. I can't recall anyone wishing they had not done that swap after they did it.

 

[booster]

Here is a typical wiring diagram for a 4 wire Hehr isolator.

https://www.texasindustrialelectric.com/pdf/33_21_Isolator_wiring.pdf

 

[roadbiker1]

Still chasing around the isolator .pdf you thankfully linked.. I'd REALLY like to see the electrical schematic of its guts, and can't find it... tried HEHR but they seem to have been absorbed / bought out /acquired by a boat supply joint ( emarine? ) and I couldn't find any schematics there.
As I understand it, the alt field needs a little initial current to get things going, then the alt's own now generated juice runs the field. OK, but then WTH is that "E" terminal doing, and how does it get the initial
current over to the alt itself? As I said, I have a test LED on the E term, and am waiting for the NO CHARGE
thing to happen...not a big game hunter, but it would be nice to get a solid kill on this ;- )
Cheers from Oregon!

j

 

[roadbiker1]

Jay,

I was able to locate the notes I have on your isolator, and the smaller terminal between the center and left studs (terminal E on dwg) should have 12 Volts on it when the ignition is turned on. If not there is a chance the alternator will not receive the 12 Volts it requires just to begin charging, the initial excitation voltage. Check for 12 Volts on that smaller stud when the ignition switch is ON during your tests.

I have attached the write up about the issue where engine battery charging was lost due to this lack of the 12 Volt excitation to terminal E.
Pete

I've put a 12v LED test light on the E terminal, now just waiting for the system to NOT work...
so far, it has been behaving ;- )

 

[booster]

 

[booster]

 

[booster]

 

[roadbiker1]

thanks for the schematics.. tho do wonder about what looks like zener diodes in the top schematic:
and still have NO idea what the isolator terminal E does. Also fighting with this site's image attach function ;- )

 

[booster]

I assume they are using those diodes as a high voltage bleed to ground to prevent too high voltage and are commonly called "avalanche" diodes for altenators.

The E terminal, AFASIK is the turn on for the alternator when the key is turned on to energize the E terminal so the isolator turns on the alternator through it's connection to the regulator.

Did you read the step by step trouble shooting guide in the link I provided? I would hope that would point to what an issue is, if you have one.

 

[roadbiker1]

I may have lost the link.... is this it? https://www.texasindustrialelectric.com/pdf/33_21_Isolator_wiring.pdf

Sans a schematic of the iso box, can't say what it should be doing, tho earlier convos I thot were saying the box only fed juice thru FatAss diodes to the 2 different batteries, the diodes keeping them from burping back thru to each other.
still concerned about the isolator box.. not seeing how the E term can talk to the alt itself and get an initial field going. The iso box seems too big to be just housing a pair of diodes... I really would like to split the little
bugger open and see.

Currently charging but still confused ;- )

j