Rooftop A/C problem

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Itascajoe

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Hello all. I have 3 rooftop a/c's that were all running this past week. The campground was experiencing power problems so the 50 amp breakers keep tripping. I reset it a couple times but stupid me I didn't shut off the a/c's. 2 are cooling but one the compressor doesn't seem to be running and is only blowing warm air. I'm thinking the capacitor may be burnt. Would you all agree? As soon as I can I'll get up there and check it.
My AC is a Coleman March 8.
 

Gary RV_Wizard

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It's the first thing to check, cause it's easy to do and you can swap the start capacitor and run module form one of the other a/c to prove it out.

It sounds like the campground was suffering from low voltage, which drives up the amps on a compressor or motor.  Normally that would not have any dramatic effect on the start/run capacitor (the breaker trips before the capacitor is harmed), but the extra stress could have pushed a marginal one over the edge.
 

Rene T

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Do you by chance use a surge protector? I would highly recommend one if you don't. Most of us prefer one from Progressive Industries. It will protect you from surge spikes.  It also protect you if the CG voltage gets below a certain point. I don't remember what that level is.  It will just shut off protecting all your electronics.  Also, they are warranteed for life.
 

Itascajoe

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Yes, I do have a surge protector on the coach. I just figured with all 3 of them starting at once a couple times that would do it. I will trade parts and see how that affects it.
 

Gary RV_Wizard

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Also, they are warranteed for life.
Yeah, but the official warranty is for defects in materials and workmanship only.  It has been Progressive's practice to simply replace failing units without question, but there are new owners now and warranty coverage was recently denied for a unit that failed for no readily discernible reason, saying simply that it "must have been" external cause. I hope that doesn't signal a major change in Progressive's business practices.
Most people don't realize it, but a surge protector is a sacrificial device, giving up its life to protect other components. Every actual surge eats away as its capability and some will simply fail from normal wear & tear. [ That doesn't apply to high/low voltage protection or other functions, just actual surges.]
 

John Canfield

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Does your surge protector have a low voltage cutout? Low voltage is a motor killer and I'm having a hard time thinking how your start cap could have been affected with your campground scenario.
 

Itascajoe

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Well, I checked the 2 capacitors start and run and they checked okay with an ohm meter so I'm at a lost. Both fans run as well just not cooling also the amp draw is only 7 amps when I turn it off and turn on a working one I get 21 to 22 amps.
 

Itascajoe

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Do you think this capacitor looks like it may be leaking? It seemed to check good. It's the run capacitor.
 

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John Canfield

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I think it's time to get an RV HVAC tech to have a look, there could be a bad relay, control board problem but hopefully not a bad compressor.

If the cap resistance is high, I think it should be okay but I'm more used to checking capacitors in electronic equipment.
 

youracman

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John Canfield said:
I think it's time to get an RV HVAC tech to have a look, there could be a bad relay, control board problem but hopefully not a bad compressor.

If the cap resistance is high, I think it should be okay but I'm more used to checking capacitors in electronic equipment.

Or do what Gary suggested; i.e.,  "borrow" the caps from one of the known good units (assuming they are the same size.....or nearly so; e.g. 13,500 or 15,000 BTU) and eliminate the guesswork re good or bad caps on the dead unit.  Pretty simple go/no-go approach.  Takes a few minutes. 

BTW- I have a capacitor tester in my tool box.  Why?  Because an ohmmeter will never tell you the capacitance (ufd) .... guess it'll tell you if it is shorted.  Granted, before the DVM age you could look for capacitive "kick" with a VOM but that just says there is "some value" of capacitance there.  Gotta admit I never tried that with a DVM, but I doubt it would work.... the capacitive kick was just a quick flick of the meter....then back to infinity as I recall ..... only been 50 years or so. lol

Good luck with the fix and safe travels................ ed s
 

John Canfield

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youracman said:
BTW- I have a capacitor tester in my tool box.  Why?  Because an ohmmeter will never tell you the capacitance (ufd) .... guess it'll tell you if it is shorted.  Granted, before the DVM age you could look for capacitive "kick" with a VOM but that just says there is "some value" of capacitance there.  Gotta admit I never tried that with a DVM, but I doubt it would work.... the capacitive kick was just a quick flick of the meter....then back to infinity as I recall ..... only been 50 years or so...
Some high end DMMs can measure capacitance, I have two or three capacitors testers for my electronics bench. An electrolytic capacitor will react differently to the ohmmeter test vs. a ceramic or non-polarized type and you are right - you switch leads and look for a kick. The ohmmeter's battery charges the cap and reversing the leads discharges.

Check out Mr. Carleson's (sp?) Lab on YouTube, you will enjoy his electronics videos. He designed a capacitor test device that I would like to build.
 

FunSteak

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We just had to replace an AC unit (under warranty, thank goodness), most likely due to low voltage.  Burnt the compressor! 

I have to vigorously second the suggestions above about having an EMS that deals with high/low voltage, not just a surge protector, which doesn't protect against low voltage.  We went right out and got one, all the while wishing I'd have done it last year. 
 

John Canfield

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When our coach was brand new I installed a permanent mount surge/low/high line protection. We've put 117,000 miles on the coach and never had one failure attributable to a campground power issue. We've had one leg of 50 amp shore power missing (several times), low voltage and who knows what else. Our campground power at one RV park in Alaska was supplied by a large generator and again when we went with Fantasy Tours for Airventure (Oshkosh fly-in.) 

Spend the money now to protect your unit or pay the price later (and if you travel enough, you WILL experience power problems at some point.)
 

Itascajoe

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So here is the final outcome. I took the coach to Camping World and they said it was a frozen compressor due to low voltage so they replaced the a/c unit and my warranty company picked up half because I had a 500 deductible. All good now I'm happy and the wife is even happier.
Thank you all for your input.
 

Itascajoe

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Hey Rene T what would you suggest for low voltage surge protector? I have an internal surge protector that came with the coach.
 

John Canfield

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Ah-so, I'm glad the other two compressors didn't bite the dust as well. Get a good surge protection device that will shut down on low voltage. Consider a Hughes autoformer for low voltage situations - it will boost voltage at the expense of lowering available current. You might not need it often but it's an equipment saver.
 

John Canfield

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I have the Progressive one as well. If you have the space, I highly recommend buying a permanent mount version, less stuff you have to drag out and put away when camping.
 
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