Hello Forum Folks, May be developing a problem with the Thomas Aux Air Compressor. Last night I'm watching a football game (LA-C v LasVegas) in the coach and the little compressor kicks on as usual. However, this time I notice a different sound, kinda like the pump is pulsating and not getting enough juice from the batteries. I turn off the pump and then turn it back on and the sound goes away. Today the pump comes on and it sounds normal, but I go to check on it and when I open the bay door I smell an electrical type burning smell. That can't be good. Get out my flashlight and examine the pump and wires. The positive wire going to the pump appears to be burning. This wire comes from a device at the rear of the pump motor that appears to be a coil or a solenoid. Hoping the fix is simple, i.e., replace the wire or is there something else going on?
The wire which is overheating is obviously the power (+) wire for the motor. A wire overheats when it is passing more current than it is designed to handle. If the motor is binding or seizing or turning against excessive resistance it will draw more amps than normal, which will overheat the power wire. Possibly the bearings are going out on motor or compressor is failing?
The item you have circled in red looks like a relay in the motor power circuit, which is controlled (opened or closed) by the wire coming from the pressure switch.
It could also overheat if the connection is loose or strands are damaged. With a short wire, just replace it with that or larger gauge wire.
Could it be a bad motor-- sure, but start with the easy (read that CHEAP) things first.
Not disagreeing with your answer, but isn't that kinda like replacing a blown fuse with a bigger fuse so it won't blow?
IF (big IF) that wire is the original wire on that compressor setup, then at one time it was the correct size wire. Now it is melting. So I guess the big question is: What has changed?
Understand your concern. But wire should NEVER be the "weak link" Fuses, by definition are there to protect the wire. I know I replaced many many feet of 12 VDC wire in our Fortravel with larger gauge for lower voltage loss. Voltage loss in a wire= resistance= HEAT.
Need to look at the complete wiring diagram for that compressor power circuit, to see if the 12V power source includes a fuse. The diagrams are not clear on that point.
If the switch "passes through" the 12 VDC positive, the fuse should be before it.
If the switch merely closes a RELAY (a much better arrangement, as full voltage doesn't hammer the points in the switch) it should be before the relay.
Please do let us know what you find.
Chuck,
The power for that motor comes off of one of the manual reset breakers in the basement hid behind the white cover. IIRC it is 15amps that powers the relay on the power side for the motor. The control side has it's own fuse.
Mike
Mike,
Thanx. In that case, perhaps the breaker has failed closed? Otherwise, it should open before the power wire at the motor melts.
I found the diagram linked below in the Forum library. Don't know if it is correct for the 2003 U320. Can't tell if the power wire has the blade fuse holder shown as stock, or if it was added on by owner.
https://www.foreforums.com/index.php?action=media;sa=item;in=1059#viewitem
That 15 amp fuse is OEM as mine has it also.
Diagram 95.39 that the OP posted showes that fuse.
Where? I'm not seeing it.
Oops, I added a 1 to that fuse but the one you posted shows it.
But I'm not sure that is the same HWH compressor as in the original post. The pressure control switch has a different pressure setting.
Do some of the newer coaches have two different HWH compressors? Or different pressure switch settings for different equipment?
I don't know enough about the newer coaches...
The OP and I have the same year coach so tomorrow I'll look at my set up and see if I can find that 15 amp fuse.
If you have a loose connection it can cause the wire to burn the insulation off the wire without causing the breaker to trip. See that happen all the time. Replace the wire make good connections, then let's see what happens.
Make sure the nut on top of the Essex relay where the power wire to the motor is attached is tight. If not remove it and clean the ring terminal and the stud. Double check the condition of the ring terminal connection while you are at it.
Thanks for all the responses. Went to an auto parts store for the 8AWG x 1/4" ring terminals and then to a hardware store for stranded wire. Ops I purchased #10 wire and didn't realize my mistake until I got home. >:( Since my wire and terminals didn't match I decided to remove the old wiring, i.e., the easy stuff. Should have done that first since the wiring had 5/16" terminals on the motor side and 1/4" terminals on the switch side and what appears to be 8AWG wiring. The positive wire insulation was a little bit burned / melted near one of the ring terminals, but was IMHO still usable. The common side showed no damage. What I did discover was the studs on the Thomas motor were loose!! I don't know much about motors but these studs screw into the case and have a 5/16" post the wire connects to. Cleaned all the terminals and tightened up the loose connections and life is good. The motor doesn't make any strange noises and seems to be running with increased horsepower. I say this because it doesn't take nearly as long to bring the system up to pressure when the pump kicks on. No telling how long the problem with loose connections has existed. Thanks again Forum Folks.