Dometic SL-135 A/C problem

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jswalls110

jswalls110

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Jan 26, 2011
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Since yesterday was the first really hot day we have had I combined testing my rooftop AC with my monthly generator run.

I was getting no cool air at all. I turned on the fan only and it works. When I switch to COOL I can hear the compressor kick on but still no cool air (the fan still runs). The coils don't even get cool.

I have read about the starter cap going bad, but would the compressor kick on at all if that is the issue?

I have an issue with height (relating to a brain injury) so getting on the roof is the last resort for me, but I will if I need to (carefully!!!).

I have checked all other connections and they appear to be ok.

Anything else I should look at before I go up and take the shroud off? What should I check under the shroud beside the 2 caps?

Thanks for any ideas.
 
Does the compressor start and run, or just try to start and quit. You should be able to hear the sound of the compressor running - it is distinctly deeper sound than the fan noise.

If the start cap is bad, you will hear it try to start and usually cut out within 1-2 seconds. If the cap is OK, the compressor keeps on running.  That also means the circuit board that controls the a/c is ok.  There isn't much to look at on the roof other than the caps unless you are an a/c repair guy, and few a/c shops will try to repair an RV a/c that is leaking, i.e. low on freon. It's basically a disposable unit. A few shops might install a charging port and try to find figure out why it is leaking, but if they can't find it within 1-2 hours of labor, it is probably best to quit and get a replacement rather than sending good money after bad.
 
The compressor stays on. As you said it is a deeper hum then the fan alone.

I thought I'd this a shot in case I missed something, but it looks like it may be shot.

Thanks Gary.
 
Here is what I found when I had a ''problem'' with my AC's.
I have one of those ''duel thermostats'' with the slides for adjusting the ''temp'' of the two Ac's on the roof.
I had a problem with my front AC not wanting to come on properly.
I carefully removed the ''duel thermostats'' thingie after un plugging all the power and the batteres to the coach.
I took this ''duel thermostat'' to the kitchen table and laid out some paper towels on the table.  I opened a beer.  (optional)
I got out my contact cleaner can with the long squirter nozzle and carefully cleaned the ''zipper type contacts'' on both temp setting controls.  (I was careful not to get contact cleaner in my beer)
While the contacts were wet with cleaner, I adjusted the controls up and down several times to ''clean'' the contacts.  I repeated this a couple of times without spilling any beer, but I did take a sip or two, of beer.

After cleaning the contacts the control lever is difficult to move because you have taken all the lube off the contacts.  To relubricate the zipper controls I use WD-40 very carefully.  I put just enough on the sliders so they will slide easily. 
I put the whole mess back in the wall and turn on the power and adjust the AC's to cold and turn them on.  So far this has always fixed my problems because this little ''control box'' is seemingly the brain and if the contacts are not working , nothing else will either. 

Mind you this is RED NECK ENGINEERING and it may not work for you.....  If you do use this valuable information you must pay me ten cents the next time you see me..........(if it dont work for you ...I NEVER KNEW YOU)........CJ....

Thank a vet for your freedom...... they bought it for you...... with their blood .....cj..
 
Thanks for the idea Seajay. Especially the beer part. I have a roof mount unit but I think I may take a look at the controls (what could it hurt, it's not working anyway?)

 
I thought I would update this.

I talked to Dometic and ES-refrigerants  (an alternate coolant manufacturer).

My unit had a access port already in.

I bought  ES-refrigerants R22 replacement coolant and installed a little (maybe 4oz).

The output of the A/C unit went from 78 to 51 in a minute, and to 40 within 1/2 hour.

The port is a cheap addon from Grainger (about $4). The refrigerant and hose cost about $60 (bought WAY too much).

So unless I have a leak (going to checking regularly)  this is a cheap and easy way to fix roof top A/C.
 

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Seajay said:
Here is what I found when I had a ''problem'' with my AC's.
I have one of those ''duel thermostats'' with the slides for adjusting the ''temp'' of the two Ac's on the roof.
I had a problem with my front AC not wanting to come on properly.
I carefully removed the ''duel thermostats'' thingie after un plugging all the power and the batteres to the coach.
I took this ''duel thermostat'' to the kitchen table and laid out some paper towels on the table.  I opened a beer.  (optional)
I got out my contact cleaner can with the long squirter nozzle and carefully cleaned the ''zipper type contacts'' on both temp setting controls.  (I was careful not to get contact cleaner in my beer)
While the contacts were wet with cleaner, I adjusted the controls up and down several times to ''clean'' the contacts.  I repeated this a couple of times without spilling any beer, but I did take a sip or two, of beer.

After cleaning the contacts the control lever is difficult to move because you have taken all the lube off the contacts.  To relubricate the zipper controls I use WD-40 very carefully.  I put just enough on the sliders so they will slide easily. 
I put the whole mess back in the wall and turn on the power and adjust the AC's to cold and turn them on.  So far this has always fixed my problems because this little ''control box'' is seemingly the brain and if the contacts are not working , nothing else will either. 

Mind you this is RED NECK ENGINEERING and it may not work for you.....  If you do use this valuable information you must pay me ten cents the next time you see me..........(if it dont work for you ...I NEVER KNEW YOU)........CJ....

Thank a vet for your freedom...... they bought it for you...... with their blood .....cj..
Click to expand...

Well Seajay, I'll have to e-mail you another dime! my slider thingys don't work very well and I was gonna try to replace the whole thing. I have to try this with my beer goggles on!

Steve
 
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