Roof A/C Problem

[travism]

> The other one does nothing when I turn it on
> to "Fan" and only hums when I turn it to "Cool". They are not the OEM
units .
> They are Model 55915-041. Any ideas ? I don't have an Owners manual but I
> think the controls and wiring diagram are very similar to the Duo Therm in
> the GMC manual. I'm looking for the nearest service dealer and that might
be
> my best move.
> Andy M
> 75 PB

I think that the first thing I'd do is put a voltmeter on the supply leads
to the a/c and watch it while turning the unit on. It seems unlikely that
both the fan and compressor would fail simultaneously while not being used.

On the other hand, I'm not completely sure that I know what you mean when
you say that it hums when you turn it to "cool;" would you recognize the
sound of the compressor running? It's not terribly loud, but is more than
just a hum. If it is the compressor that you're hearing, chances are the fan
motor is your only problem. Try pulling the cover off of the unit and
spinning the fan by hand (with the power off, of course!) If it doesn't turn
freely, look for obstructions, perhaps twigs or leaves, and lubricate the
bearings well. This may solve your problem. While you're up there, lubricate
the fan motor on the other unit---they need it periodically.

Travis

 

[ritch hwang]

Andy,

I had a similar prob in the past. Visions of spending big $$$ for a fix
abounded. Pulled the shroud - everything looked ok. Wiggled a few wires
and one fell off. The terminal for the fan motor had hairline fractures at
each side, preventing good contact - but it *appeared* to be ok. Replaced
the terminal, repainted the shroud, buttoned it back up, still working
great to date.

Hope it's that simple for you too!

Ritch
76 Birchaven

On Sun, 4 Jun 2000 17:46:37 EDT

 

[alan bredbury]

My roof air does exactly what you describe. When I turn it
on hi cool it hums (compressor) and does not blow. I have
not bothered to find out exactly what the problem is
because if I switch it between lo and hi cool a couple of
times the fan comes on. I am assuming that I simply have
dirty or worn contacts on the switch.

=====
Alan Bredbury
Clinton, Ct.
1974 GMC 26' Classic Motorhome
http://www.finesttool.com/index.html/special.htm

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[emerystora]

> Haven't found my A/C problem yet but have received many good ideas from
>the net. Surprising how well this works. Just post the question and some or
>many have had similar problems and offer solutions. I'm pretty sure the
>trouble is with the fan motor.

You can download a DuoTherm Air conditioner diagnostic guide that
gives suggestions on what to check for solving air conditioner
problems at:

http://www.rv.com/pdfs/os1362.pdf

In the case where the compressor hums but the fan doesn't run it says:
Wiring, switch, run capacitor, motor.

Emery Stora
77 Kingsley
Santa Fe, NM