On a recent trip I noticed my dash volt meter (and VMSpc) would drop to about 12.2 v and then jump up to 15.2 v for just a second or two and then stabilize at about 13.5 v. This process would occur about twice a minute. I turned on the generator to run my roof A/Cs and to see if that changed anything. It didn't change much but did slow down the frequency of the jumps. I called the factory, they told me to check voltages at the isolator, they seemed fine. However, I was checking with the dash air off. After a short time on the road I turned on the dash A/C and noticed immediately that the voltages were jumping again. So I turned off the air and all was fine. Every time I turned on the dash air it would start to jump within a few seconds. I have been reading the forum and think this might have something to do with the alternator sense wire. I emailed the factory this morning but I have not received a response yet. Any ideas?
My coach was doing the same thing. It turned out to be my condenser fan. The circuit breaker was self resetting and the voltage would drop when it was on and go back up when the breaker was off.
The dash air seems to be working fine, do I change the fan or the breaker?
Start the engine turn on the air and watch the condenser fan and see if it is starting and stopping. My fan was tripping the circuit breaker even though the air was cold. The fan cycled enough to keep the dash air cold. It took me a year to figure out what was causing the voltage swing. In my case it was the fan drawing to much power. The fan didn't spin freely like the new one did.
Could also be the same scenario with the AC clutch,check that too,cycling on and off.
Several of us have moved the sense wire location off the A/C circuit to a better location. Doing this will cure the false reading of the state of batteries when the A/C cycles on/off.
Mike
Where did you move it?
I put ours on the lug of the isolator that has the cable that goes directly to the start battery. If you use this location make sure that you use a new self resetting breaker in the wire.
Mike
The same thing happened to me and it was the condenser fan and when it fail it shut the engine off. It was on the same breaker as the ecm. Needless to say that is not so any longer.
You might want to re think that self resetting circuit breaker. The FAA issued a notice, I can't remember what level, and I certainly can't remember how long ago, to not re-set a tripped circuit breaker in flight, after several inflight fires had occurred.
OT,
I can't see not adding one more self resetting breaker to a coach that has over 40 will make a big difference.
Mike
Beavers had self resetting circuit breakers for a lot of coach functions.
And a marine 12 volt breaker panel also.
No problems
It took me a while to do some digging, but I did the test requested by craneman and realized that the condenser fan was the problem as described. Thank you so much! Headed out today to find a replacement. Also, looked at relocating the sense wire and it appears that project has already been done by the PO. I tried to upload a picture, but not sure it worked, but anyway I noticed that the compressor breaker (the one on the end for my year model) has nothing on the end terminal, not even the nut. The compressor does work but not wired through this breaker. I noticed in the battery compartment that a wire with an inline fuse is connected to the positive terminal and wired to a relay that is strapped to the chassis. I can't see where the wire goes except into the engine bay. Any ideas?
Thanks everyone for your help.
I see the picture uploaded. The terminal I'm talking about above is labeled #2. Can anyone identify ALL the parts on this picture by number for future reference?