1992 Damon "Challenger" Gen Set battery dead

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B737doc

B737doc

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Jun 29, 2017
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71
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West Georgia
    Bought our motorhome 8 days ago, everything works great. Went camping for 3 nights, now gen set will not do anything.  Checked the 2 batteries under the hood that seem to be wired together,  one reads 13.4 VDC, the other only .43 VDC.  The gen set had been starting just fine, and turned over strong until we connected to shore power at the park.  Don't get it...
 
I think you have a meter problem

The Gen-Set should start based upon the house battery..

IF those two batteries are actually wired together they should be the same voltage and it should not be possible to get different readings unless you disconnect them first so assuming you did.

Check to see if one of the steps (likely the top one) Folds up and has more batteries under it. May be latched down.. Those will be the HOUSE batteries.
 
  I've only been able to locate 2 batteries mounted underneath the hood of the vehicle, mounted in front of the engine that appear to be wired in series.  The left battery shows only .043 VDC, whereas the right battery shows 13.4 VDC, and that's with everything connected.  Attached external battery charger to left battery for 3 hours, gen set started right up, but left battery shows 11.82  with gen set on line, neither battery appears to be charging. 
  Steps going into the vehicle seem to be solid, with no obvious access to anything.  Maybe the main engine charge the only batteries I can find, but if so, the left one was DOA upon arrival from 42 miles of driving....
 
Check that all the cables connections are clean and tight corrosion free.
 
Even connected in series a battery with a dead cell (open) can measure a different voltage than its pardner. Neither battery will charge in this situation. I just replaced one of my golf cart battrries (out of six) with just this condition. I identified the problem by measuring the voltage across each battery. Replaced the low one.

Ernie

Note that batteries should be replaced in sets but with $900+ worth of batteries in a two year old cart, I elected to risk ruining the new one, an el cheapo, since a few months of extra use for the five other batteries makes it cost effective.
 
B737doc said:
  I've only been able to locate 2 batteries mounted underneath the hood of the vehicle, mounted in front of the engine that appear to be wired in series.  The left battery shows only .043 VDC, whereas the right battery shows 13.4 VDC, and that's with everything connected.  Attached external battery charger to left battery for 3 hours, gen set started right up, but left battery shows 11.82  with gen set on line, neither battery appears to be charging.
Click to expand...

Connecting two 12 volt batteries in series will give 24 volts, and there's nothing in the RV that uses 24 volts.  It's much more likey they're wired in parallel.

With parallel connected batteries, any corrosion in the connections between the batteries will open the circuit between them.  It sounds like the right hand battery is your house battery, with an isolation solenoid between it and the engine battery that's supposed to close and connect them together when the engine is running so the alternator can charge them both.

The generator does not produce 12 volts, most installations power the generator from the house batteries, which are charged by the house converter when the generator is producing 120 VAC.  They're also charged by the engine alternator when the main engine is running.

Make sure all of the connections are clean and tight, including where the negative wire from each battery connects to the chassis.

If this doesn't solve the problem, you'll have to physically trace the positive wire to see if there's a bad connection or possibly an isolation solenoid that's not pulling in when the engine is running to connect the right battery to the engine alternator.
 
  So the ENGINE should charge both batteries when running???  Found out that I had left some interior lights on...They still should have been fully charged after a 45 mile drive...
 
The engine alternator activates a solenoid that connects the house and chassis together when the engine is running so the alternator can charge them both.  If the solenoid is bad the main engine's charging voltage won't reach the house battery.

Leaving some lights on can drain the house battery, which also feeds the generator.  Did you have voltage on the lights when you tried to start the generator?
 
Still feel like it should have been > .043 VDC.    I love electrical issues!  Will find fix and post.
 
    This RV has no "house batteries".  The only batteries on this vehicle are the 2 underneath the hood, and both have individual grounds to the frame.  The 2 individual positive leads disappear behind the fire wall to somewhere, apparently starter relays for the engine and gen set.  With the engine running, one battery shows positive voltage, the other is slowly falling from 11.82 VDC. 
  I see two relays bolted to the firewall, and check for voltage at the control wires for each relay. I have voltage at one, but no voltage at the other. I follow the wire with no power, to the "Aux Start" switch on the console. Turns out, this switch is springloaded to the off position, and provides power to the relay that interconnects the two batteries when pressed.  I connected the control wires for both relays together with a jumper wire, and now, BOTH batteries are showing positive voltage from the engine generator with the engine runnng at idle.
  I assume this "Aux Start" switch provides additional voltage for starting when pressed.  Don't understand why only one at terry is getting a charge.  Started and loaded gen set, still no positive voltage. 
 
The second battery under the hood is the house battery.  It has the lights and other house loads connected to it so you can drain it down while camping and still have a fresh charge in the chassis battery to let you start the main engine.

The generator is connected to the house battery so you can start and stop it while you're camping.  The chassis battery just sits there, it doesn't get a charge unless the main engine is running so you don't want the generator's starter running it down.

The relay with power to it's solenoid - it's defective unless you have the same voltage on both of the large terminals when it's energized.  It's supposed to connect the batteries together when the main engine is running, so the alternator can charge both of them.

The Aux Start relay does the same thing, the reason they used two relays instead of one is to keep the control voltages separate.
One comes from the alternator voltage, the other from the house battery through the Aux Start switch.  By connecting the two control wires together you created a path between the house battery system and the chassis battery system that bypasses the large current relays.

Beyond that, you should verify that the house converter is putting out voltage, approximately 13.5 VDC when there's 120 VAC feeding it, otherwise all of your house loads are just running off of the house battery.
 
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