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rand1 · 08-03-2017, 06:28 PM

I have a 1991 national rv, that is not charging house battery while engine is running, I replaced the isolator solenoid with no results then I replaced the relay delay isolator controller still no results. The voltage on center post of solenoid is 13 volts and the two big terminals on the side of solenoid is 11 volts. The chassis battery with engine running is receiving 13 volts so it appears the alternator is working. Is there anything else in the charging circuit I can check?

Kiawah · 08-03-2017, 07:04 PM

I don't know your coach, but I would suspect there could be a fuse in the circuit. I have a big fuse (like 300 or 400 amps) on each battery end, of the cable that connects the two banks together.

RKins · 08-04-2017, 01:48 PM

I am not familiar with your coach but I think the Alternator only charges the Chassis batteries. The BIRD and Iso Relay work with generator and shore power and focuses on house batteries first. When they are charged to a certain level the Iso relay combines the banks to charge both.
Do your house batts charge on shore power?

twinboat · 08-04-2017, 02:07 PM

If your reading 11 volts on both large terminals with power to the small center terminal, the relay is probably working.

Go to the chassis battery and look for a large cable. Not the one going to the starter.

If it is there and connected, follow the battery cable, that doesn't go to the starter, and look for a HI AMP circuit breaker ( about the size of a deck of cards ). It may be tripped.

It seems that the chassis battery isn't connected to the relay and your only reading ( low ) house battery voltage.

nothermark · 08-04-2017, 02:12 PM

I question whether or not you looking in the right place. If the solenoid has the same voltage on both big terminals it is closed and working. 11 VDC would tell me it is connected to the house batteries and they are low.

There should be a heavier wire from the alternator to a big relay then on to the house battery bank. It will have a fuse or circuit breaker close to the alternator. The delay board controls that big relay. You need to find that relay and the wiring associated with it and figure out where you are losing the 13 V from the alternator.