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mgtibb · 08-03-2021, 04:31 AM

Having a strange problem with starting motorhome. Turn the key and nothing, acts like completely dead battery but there is 12.7 volts at chassis battery. Push battery boost and everything comes to life, starts and runs fine with 14.1 volts on both chassis and house batteries. I have replaced both the Bird controller and isolation solenoid but it still does this. Problem is intermittent. Last night after turning off engine, maybe 40 mins later I hear dash clicking and radio going off and on and look at voltage on panel is at 8-9 volts jumping around. I push battery boost button and hear a clunck from engine bay and voltage is back to 12.9. Anyone have any suggestions as to what might be going on?

twinboat · 08-03-2021, 05:25 AM

Chassis battery bad or connections bad. Check and clean both ends, positive and negetive. Have chassis battery tested.

You can't see corrosion on battery terminals unless you remove them.

It has nothing to do with the BIRD. When you push the Boost switch, you combine the well connected house batteries to the poorly connected or bad chassis battery.
Once running both stay connected thru that same solenoid but controlled by the BIRD.

Sometimes a bad connection will seem to fix itself with a voltage surge, like the boost switch, and burn thru the corrosion and work for a while. When it don't, feel the connections for heat. That's the bad one.

scbwr · 08-03-2021, 06:34 AM

Check the battery with a load test. Also, look for any ground connection from the battery and clean it. Judging by the low volt reading at night, I think you have a battery that isn't holding it's charge. Have you used a battery tester to check the charge level of each cell? I tend to think you might find you have a bad cell.

If it is the original battery, it may be time to replace it. I think I would just get a new battery and see if that takes care of the problem. If I were to clean all connections and replace the battery and still have problems, it would be time to take it to a good repair shop.

mgtibb · 08-03-2021, 09:05 PM

Thanks for the replies. I bought a new battery today and will see if that fixes the problem. I cleaned the battery connections when this all started happening but will do it again and check for loose connections when I install battery. Does anyone know where the chassis ground is? It looks to run along frame by wheel well and toward the top of the engine. I imagine I will have to remove dog house to find where it is grounded.