Generator won't start. Electrical connections?

Sturedman · September 23, 2013, 07:43 AM

I bought this RV with no batteries for anything. He gave me service records that show the Onan had been sent to Cummins and rebuilt. Over the weekend I bought a couple of 12V deep cycle batteries to eventually convert to solar. I hooked up one of the batteries, and all the lights worked in the coach, the water pump and the fridge on 12V, so I was happy with that. I tried to start the generator and there was nothing. The rv had 2 batteries and I have to sets of cables. One set has the "eyelets" on the end connect to the battery. The other set is regular side post connectors. My question is, do I need those side post cables to also be connected to a battery in order for the generator to start? Here are a couple of pictures if it helps to understand what I am trying to say lol

If I need to hook up the side post connectors, I will have to buy another battery.

Madathlon · September 23, 2013, 10:18 AM

While hard to tell, the side post is most likely for your MH engine to crank and run. Now you said the gen wont do anything, is this using the remote start in the RV or the start sw on the genset?

Sturedman · September 23, 2013, 10:24 AM

I tried it in both places. Neither one even tried to start the genset. That's what had me perplexed lol

DaveVA78Chieftain · September 23, 2013, 01:36 PM

The positive cables from the batteries (chassis and coach) should be routed up to the AUX start solenoid at the top of your picture. One side of the solenoid is for the house & gen (house battery). The other side is for the engine (chassis battery). One of the large cables on the house side of the solenoid should go to the generator.
Dave

mnoyes · September 23, 2013, 06:03 PM

i dont have a technical answer but i do know that on my rig i dont need to have both hooked up....when i bought my mh it only came with one battery so i just switched cabels to make sure the generator started....

Sturedman · September 23, 2013, 06:24 PM

I was afraid of that

. Thank God for solar panels. I don't have a clue why it won't start, but the lights work, the water pump works and the fridge works!! I guess that is the most important, and I have another generator in case of an emergency!

Madathlon · September 23, 2013, 08:03 PM

OKay, Sorry for the slow responces, Been helping a friend install a new gen in his rv.

What I need first is Make and model of the gen set.

If its Green its a Onan. There will be either a silver and black tag on it with the Model and Spec letter on it OR a metal tag with the same info. From there we can get into how to find the issue and fix it.

Sturedman · September 23, 2013, 08:20 PM

Well, thank you very much Madathlon. Very kind of you indeed. I will be back out to the property this weekend, and I will get that info for you, and take a couple of pictures. It is green, and he had sent it to Cummins for service before the engine (454) went bad on him. He said it had a rod knocking, but again, no batteries, so I've never even tried to start it. Traded him a Glock 21 that I had paid $400.00 for, and had it towed out to the property a couple of months ago. Only about 150 hours on it since the rebuild on it from what I understand.

Sturedman · September 30, 2013, 08:48 PM

Quote from: Madathlon on September 23, 2013, 08:03 PM
OKay, Sorry for the slow responces, Been helping a friend install a new gen in his rv.

What I need first is Make and model of the gen set.

If its Green its a Onan. There will be either a silver and black tag on it with the Model and Spec letter on it OR a metal tag with the same info. From there we can get into how to find the issue and fix it.

Sorry for the delay Mad....only get out there on weekends lol. Here is a couple of pictures. It's difficult to read but the model and spec number is - 4.0BFA-1R/16020C. The serial number is - K803538363,

I don't know if it matters, but this one tells me if I am not using shore power, but using the generator, the plug has to be plugged in to the receptical in the motor home where the cord goes.

Madathlon · September 30, 2013, 09:21 PM

Sweet a BFA, while a older genset this unit is above all the newer one, First its a slow turner running only at 1800 RPMs, New GEnset are all running at 3600 RPM.

Now first thing first, you should have two glass fuses on the front housing, check these to make sure thier not blown. (One of them is for cranking and it one start without that fuse)

If not blown we can move on to a few other easy test.

First off you need a few tools.

Sockets Set (SAE Type)
Wrenches (SAE Type)
Screwdrivers, One Philp and one flat head
12vDC Test light or 12vDC Volt Meter
A jumper lead, (Speaker wire will work for this)
A pair of Jumper cables and one louse 12v Automotive Battery with no less then 400CCA

This genset does NOT have a starter as you have seen in cars and trucks, The starter is the Main Gen Rotor itself.

After removing the cover you will find a Solenoid that the incoming 12vDC heavy batter cable come to. With your test light see if there is voltage at the solenoid, if Not then your problem is outside of the genset and you will have to get under the RV and follow the Batt cable back to the Battery box.

IF there is voltage at the side that the cable comes in we then have to test the solenoid. Place your test light on the other large stud on the solenoid and press the start sw.

IF this suddenly lights up the solenoid is good and that leave the main rotor and brushes to be check.

IF it doesn't light up you have found your problem and you will need to remove the solenoid and take it to a automotive parts store and match it up for a new one. (Likely its a 1970's Ford starter solenoid).

IF you come to this point there are other test to perform and it is complicated to go over.

But do not just give up. I will go over this more if you have to get into the main rotor assy.

DaveVA78Chieftain · September 30, 2013, 11:11 PM

The BFA Service Manual (900-0337) is available in Members area under Free Manuals, Onan. Just scroll down to the Onan BFA listing. Makes this discussion a lot easier.

There is also a version at http://asavage.dyndns.org/Onan/display1.php?Path=900-0337&db=Onan&table=900_0337 however the presentation format is difficult to use.

Dave