Batteries won't charge with engine running

[Detect15]

Sent: 9/29/2003

Thanks all for your help and advice in the past.  I found out that the coach battery's are not being charged while the engine is running.  I have 2 pretty large deep cycle batteries that run the coach.  I charged them manually today with a 10 amp charger, almost to full capacity.  I took a long test drive, with the dual/mom dash switch in the dual position.  While the engine was running, I noticed that the charging indicator light on the coach fuse panel was not lit.  Also when I returned home, I checked the charge of the batteries with a tester, and noticed the charge had declined quite a bit from the start of my trip.  I hooked up the manual charger, and noticed that the charging light on the coach fuse panel, indicated that the system was charging.

I'm not sure where to start to diagnose this problem...a faulty dual/mom dash switch?a burned out converter (which I think is behind the coach fuse panel), or a bad line from the alternator to the converter?  I have had no problems with starting the engine, always plenty of juice in the engine starting battery.  Also, when I purchased the the RV, it had one coach battery that was shot, so I replaced it with 2 -12 volt deep cycle batts from Sears.  Could this contribute to the problem???

Thanks so much for your comments.

Earl 

[denisondc]

Sent: 9/29/2003

The only way the 2 12 volt batteries could contribute to the problem would be if one or both were defective. Very unlikely. I presume you have them wired in parallel.
That you might have something in the coach that was always draining power from the coach batteries - more likely. It could be a circuit for the furnace or refridge or whatever, that someone wired-on due to a bad switch or fuse, then forgot about, or a defective component in some 12volt using part. for example I had a florescent light fixture go bad and keep on drawing power, though the bulb didn't light. Do you have any 12v fan motors that are warm and should not be? On a dark night, disconnect the coach batteries, and see if there is a tiny spark when you do the disconnect/connection - I think there should not be, if your accessories are shut off.
That your coach batteries aren't charging when you have the dual/mom switch in dual means there is a breakdown somewhere in that normal scheme. I think there would be a relay near the batteries that the dual/mom switch would pull-in to connect coach and engine batteries, but it may have been rewired or hay-wired at some point, in addition to normal wire connection aging. Yours must be newer than my 72 D22, which doesn't have a coach charging panel. But on my 72 I am frequently chasing bad connections, corroded wires.
I would begin with the positive coach and engine battery cables, and find the relay that connects them - and see if it is getting a solenoid voltage when the dual switch, and your ignition are on. Of course the solenoid and the coach batteries should all be well grounded too. My coach battery is grounded to the coach light circuits only via an undersized relay hidden in the guts of the 12v converter. Had to clean it once before my coach lights would work off the coach battery. good luck and stay in touch
denison

[Detect15]

Sent: 9/29/2003

Thanks for the info Denison..

While looking into it further, I found that the Onan Genset when running, indicates a reversed neutral/hot wire, when I tested the interior outlets with a 110 tester.  Could this contribute to the problem overall?  Their is an outlet inside the genset compartment that indicates a correct current reading, but the coach outlets indicate otherwise.  Also, I'm not sure or know how to test to see if the genset is properly charging the house batts, other than the red charging indicator light on the fuse panel.  It is lit when running genset, but goes very dim when I put the AC on.  I think this is normal.  Also, I'm not sure how to re-wire the genset output wires, in order to get a proper reading other than just reversing the wires and re-testing the circuit.

Thanks again for your help!   

[denisondc]

Sent: 9/29/2003

I cant think a reversed neutral/hot wire service would have any bearing on the coach batteries not charging while the engine was running. However my genset doesn’t have a 12 volt output, nor does it charge the coach battery when it is running. I am happy with the arrangement. I carry a small battery charger to plug into the coach 120v outlets, if I need more charging than I can get from the engine alternator in a days running. The way we use our winny we don’t need the coach battery much. Therefore I can only guess about such charging circuits.
As for your apparent reversed neutral/hot wire, I would look in the circuit breaker panel, and see if someone connected a black/white pair backward. The wiring in the circuit breaker panel will probably look slightly different from house wiring, because the circumstances are different â€" the genset and the shore power cords are alternate â€"power sources-, which houses don’t have, or very seldom have. In my winny the white and the black wires each go through separate but ganged circuit breakers â€" definitely unlike house wiring, where only the black wires ever get connected to breakers. Its easy to get confused. And the wires from the genset might not be the conventional black, white, and green. After all, it’s a power source, different from an appliance.
I would advise doing separate continuity checks of your hot circuits, your neutral circuits, and your ground circuits â€" With All Power Disconnected and the Genset Stopped of course! With the circuit breakers open and appliances off, the left blade of each outlet should only be connected to all the other left blades, etc. And when you are about finished and plug your shore power cord back in, please do a voltage check between your Winnebago and the ground it is parked on!! denison

[HAL]

Sent: 9/30/2003

IT SOUNDS LIKE YOU MIGHT HAVE A BATTERY ISOLATOR BAD. YOU DIDN'T SAY IF YOUR CHASSIS BATTERY IS CHARGING.
LOOK BEHIND THE BATTERY TRAY AND YOU WILL SEE THE ISOLATOR. THERE SHOULD BE A RED WIRE COMING FROM IT TO THE COACH BATTERIES  POSITIVE SIDE AND ONE TO THE CHASSIS BATTERY POSITIVE SIDE
TAKE  A VOLT METER AND SEE IF YOU ARE GETTING 13.2 TO 13.6 VOLTS DC POWER FROM EACH SIDE OF ISOLATOR WITH ENG RUNNING AND SWITCH IN DUAL POSITION. IF YOU ARE GETTING POWER TO ONE SIDE AND NOT THE OTHER YOU HAVE A BAD ISOLATOR OR NO CONTROL POWER TO THE ISOLATOR.
SEE IF YOU ARE GETTING POWER FROM THE DUAL SIDE OF THE SWITCH TO THE ISOLATOR.
                       HAL