Removing an under mount generator (Part One)
Part One will detail removal of the generator
Part Two will detail repair and replacement of the parts
I have a 2001 Roadtrek 190 Popular with an under mount Onan 2.8KV (series F) gasoline generator. It wouldn’t even crank over so I suspected a problem with the starting circuit. It has a remote start, which can cause this problem if it is defective. The remote start can be disconnected by unplugging it at the generator. This allows you to eliminate one of the starting components and then you start it at the rocker switch on the generator itself. Still no luck. There is not much you can check through the service door, so I had to drop the generator to really diagnose the problem.
Before I continue be forewarned that this is a major job and requires at least average mechanical abilities, an understanding of how the generator and its systems work and ability to test components. This is a narrative on my set-up. Your vehicle and generator may vary. I put my RV on a series of wooden ramps to get it about 5” higher. This allowed enough height to work without being claustrophobic, and more importantly, it allowed enough clearance to pull the generator out from under the RV. Plan ahead and measure the height of the generator plus and dolly or jack that will be supporting it from underneath. Also figure out if you will wheel it out from the back or side.
First identify your unit (model number, series, serial number etc.)
You will need several manuals: a service manual, and a parts manual are definitely needed (a wiring diagram is in the parts manual). An instillation manual and operator’s manual is also helpful.
Manuals can be obtained here.
Disconnecting the generator
DC power cables 12V
There are two power connections: a positive cable, which goes to the house battery and a ground connection which attaches to the metal base pan, which supports the whole generator.
First, disconnect the positive cable at the house battery. Cover and secure it so it cannot touch the terminal. The positive cable is in two pieces. Once you locate the cable under the chassis you will see an enlarged and taped section. Inside are two lugs connected together with a screw and nylock nut. If you disconnect it here you will not have to take the cable totally out of the battery box, however, make sure you also cover and secure the end by the chassis.
The ground is a large stranded cable that comes from the chassis and is bolted to the bottom pan.
The fuel line is ¼” inside diameter rubber fuel hose that is attached to the top of the fuel pump with a clamp. Loosen it and remove the rubber hose from the metal fuel line. This rubber fuel hose comes from the main fuel tank and must be plugged so it does not leak. I inserted a bolt in the hose and then put a clamp on to tighten and secure it. Make sure it is not leaking!
AC power cables 120V
These are the cables that go from the generator to your electrical, circuit breaker box inside your RV. On my generator the wires are encased in a large grey covering and go forward up into the chassis, through the floor of the RV and finally to the circuit breaker. There are three wires; green-ground, white-neutral and black-load. On my RV, the only way I get 120V is if the generator is running or if I’m plugged in to shore power. I do not have an inverted in my unit. Before you remove the circuit breaker cover, make sure you do not have 120V going into your circuit breaker. After I opened up the circuit breaker cover, I loosened up the ground clamp holding the green wire and removed the white and black wires from their respective wires by undoing the wire nuts. Put back the wire nut and tape it to the respective wire.
Now I prepared the wires so they can be pulled through the compartment and through the chassis. I taped all three wires together and put a long piece of parachute cord on the bundle. I take about the first 6” of the cord and tape the second 3” on the bundle, then I double back the first 3” inches and also tape it. (Essentially the cord goes down then doubles back on itself so it cannot simply pull out.). You will need this cord to reinstall the AC wires so just leave it in place from the electrical compartment to the generator. Once you have all the wires out, just cut the cord, but leave enough to do the same set-up when you re-install them. My grey covering was about 2’ long and then the wires extended out about 2’ more. They just disappeared up into the chassis and eventually entered the inside of the RV. Unless I had a cord left in place, I could never insert the wires into the hole. (I couldn’t even see the entry hole!) Your set-up may be more straightforward.
Remote start wiring
This was simply a multi-wire two-part plug that just snaps apart.
Once all the connections are disconnected, zip tie them to the chassis so they are secure.
Removing the exhaust
Loosen the “U” clamp nuts. They will probably be rusty and snap, if not, use a cutting wheel to cut the round part of the clamp. Getting the exhaust pipe separated from the muffler can be tough. I gently swung it back and forth until it loosened. Then I started to bring it down off the muffler with the help of a mallet.
Dropping the generator
My generator weighs 113 pounds so some planning is in order. I used a garage type, automotive jack to support it then lower it. There are four flange head bolts, two on each side that connect the side plates of the mount to the generator pan…and they are all rusted. I sprayed PB Blaster penetrating spray for a week before I tackled these bolts. The best-case scenario is the bolts come out, second is they snap off cleanly, which will still allow the unit to drop, and last is the bolt head rounds off. Despite the penetrating oil, three of the bolts snapped off and on the last one the bolt head rounded. I used a Sawzall with a metal blade to cut between the mounting plate and the generator pan. I was only able to get a minimum amount of clearance because the other bolt was out. I placed some wooden wedges to widen the space between mounting plate and pan. The fit was tight, but it finally cut through. If both bolts on the same side had rounded off, it would be a serious problem because these are flange bolts and the bolt head is extremely difficult to cut off cleanly.
The generator was now resting on the jack and being supported by the side plates. You have to make sure the jack is centered or else it will tilt to the side when lowered and can slide off the jack. On my unit, there was more weight toward the muffler side so I had to offset the jack a bit. So be aware of this side-to-side weight balance. A second person is helpful for this part. Once it was down I was able to wheel the jack with the generator out from under the RV.
Removing the cover
The cover is held on with 4 torx head screws…and they too were rusty. Two came out and the other two rounded out the torx corners so they had to be drilled out. Drilling out the bolts required a cobalt drill and I went up in size. The torx depression helped to keep the drill centered. Once the cover was removed, I tapped the hole to accept a new screw.