Roof air conditioner only runs for 30 seconds

[Boise_Chief]

Sent: 7/7/2005 2:48 PM

Does anyone know anything about AC?  I'm fiddleing with my AC on top of my Winnebago and am having problems.  The compressor will run for about 30 seconds and then shut off.  When it is running I have 115v to common 5 V to run and 220 to start.  When it shuts off i have 115v to all of them from ground.  I can't figure out what is the problem.  I know just enough to know I don't know what I'm doing but if there is anyone that can help me find out the problem I'd appreciate it. 

The cost for a service call is going to be close to the cost of a new unit.
I'm trying to decide if its low on coolant,  Bad thermostat, or bad compressor.  I replaced the Start capacitor and relay with a 3 in one.
Thanks Sean

[OldEdBrady]

Sent: 7/7/2005 7:41 PM

I don't know much about a/c.  But, the in-house units were doing the same thing about a month ago.  Start; run a while, stop.  She Who Must Be Obeyed was out pricing new ones.  I was agin' it, since the units I have are only about 2 years old.  So, I pulled the filters out, cleaned them, and they run like new.

May not solve your problem, but thought I'd throw that in, just in case.

[Daved27c]

Sent: 7/8/2005 10:26 AM

Sean;

A couple of obvious questions. First, is the thermostat set to the coldest setting? I'm sure the answer is yes. Next, is it warm enough in the Winne for the compressor to stay running? Again I'm sure the answer is yes. After the compressor shuts down, does it ever restart on it's own? In my VERY limited experience with A/C units if it low on coolant the compressor will cycle on and off. If the compressor does not come back on then my guess would be the thermostat. It is probably telling the compressor that it is cool enough and does not need to run. Again I don't know alot about these units.
 
Also, If the A/C unit on your Winne is a Duo Therm model 53212-054 or 53212-055 I have the original wiring diagram if that would help.

Dave

[Slantsixness]

Sent: 7/8/2005 10:36 AM

Sean,
What model AC unit is it, coleman or Duo-therm?
There is a thermal fuse (round, under the plastic wiring cover) on the compressor that goes bad and would cause this to happen, but usually the compressor won't even start after it goes, could be intermittent or corroded wiring at the compressor.

Low freon will shut down the compressor, and if the condensor fan is froze up, the whole unit will shut down, check that the blower and condensor fan (usually one motor for both) is free and running.

If the thermocouple from the temperature control (the little silver bubble on the end of the copper line) opens up, that could cause the compressor to cut out, too.

Hope that helped!

Tom

[004me2]

Sent: 7/8/2005 10:40 AM

sean
check you shore power . if you are on to lite a cord that will do it to
                     jim clark

[Boise_Chief]

Sent: 7/8/2005 8:33 PM

I have a coleman in a 72 chieftain.  I believe the compressor is getting tight.  I replaced the start capacitor and now it starts fine and then only runs for about 30 seconds and then shuts down for 2 mins and then restarts.  I was up there yesterday and realized the new start cap. essentially wired around/out the run cap.  I called the place I bought the 3 in one start cap. and explained it and they told me they sold me the wrong start cap. and so I went down and picked up a new start cap today and will wire it in in the morning. 
The new one is much more difficult to wire in and I'd appreciate any help on wiring a ac compressor.  Unfortunately since I removed the old start cao and have messed up the wires it will bwe interesting.  I have a 50 50 chance of getting it right.  I am now not sure which wire is the line wire and which is the common.  wish me luck the wiring is not correctly color coded and it's a little hard. 
I'll update tommorow am and let you all know.

[Boise_Chief]

From: Boise_Chief2 Sent: 7/10/2005 11:07 PM

Ok so here is the update.

I replaced the start capacitor and relay with a two in one starter power pack.  It is a Supco SPP5.  It is designed to replace the relay a start capacitor as well as increasing starting compressor torque by 300%.  It is up and running and has worked all day.  I suspect my compressor is getting tight and caused the start cap. to fail.

The cost was $8.00.  I picked it up at a local supply house that does hvac etc. 

From the conduit from inside controls the wires are:
Black- Common
Sm. Red is line to blower
Green is Ground
White is line   This leads to fan cap/relay and ties to the start and run capacitors.

The common ties into the overload/overheat on the top of the compressor and compressor common.

The new unit has 2 wires that connect to each side of the run capacitor.  The side of the run cap. that the power line runs into also connects to the run post on the compressor.  From the other side of the run cap you run a wire to the start post on the compressor.

Once i was able to figure out which wire was which it was fairly easy.  I had been ready to throw it away and buy new but I should make it another year or so.

Hope this helps someone in the future. 

[mightybooboo]

Sent: 7/11/2005 12:47 PM

Great job Boise,thank you! Im sure that will help members in the future.

BooBoo 

[M & J]

She who must be obeyed....  I married her clone... Glad to know I"m not alone