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Open Roads Forum  >  Tech Issues

 > Turn on my A/C and it just goes hummmm...

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Damdifino

Comfort, TX

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Posted: 09/06/18 08:49pm Link  |  Quote  |  Print  |  Notify Moderator

I've been having A/C anomalies this summer, which I thought I'd fixed. First, it tripped the breaker, so I cleaned the coils, changed the circuit breaker, and it ran good for a couple of weeks. But now, I turn it on and it just hums, like it's struggling to start up. What should I look at?


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72cougarxr7

Northern NY

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Posted: 09/06/18 08:57pm Link  |  Quote  |  Print  |  Notify Moderator

I had a similar issue with my Dometic ac, ended up being a "run capacitor". Found one on Amazon for $10 shipped to my door. Working great now.
Just put your model number into one of the online parts places and find the part number.
Shop around with that part number, Amazon, Ebay etc. You will find a good price that way.

newman fulltimer

louisiana

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Posted: 09/06/18 09:04pm Link  |  Quote  |  Print  |  Notify Moderator

Need a new fan motor

ScottG

Bothell Wa.

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Posted: 09/06/18 09:30pm Link  |  Quote  |  Print  |  Notify Moderator

Exactly what mine did when the start cap died.


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lostbytes

Was lostmarbles years back on here....

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Posted: 09/06/18 10:09pm Link  |  Quote  |  Print  |  Notify Moderator

ScottG wrote:

Exactly what mine did when the start cap died.


Yup. You not getting enough help from the capacitor. You'll need an soft start capacitor. It used to be you'll need an hard start capacitor but the newer soft are a little easier on the motor windings. Older ac usually needs some extra help because they wear out and need more wattage to get going. Just get one and hook it up piggy back to the original capacitor. Look up on YouTube/Google search about how to hook one up on an RV ac.
https://www.loveyourrv.com/installing-hard-start-capacitor-into-my-rv-air-conditioner/
Here's one on hard start.

If one of those original caps is bulging then it need to be replaced first. Then try ac. If problem not solved, then add soft start.

marcsbigfoot20b27

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Posted: 09/06/18 10:56pm Link  |  Quote  |  Print  |  Notify Moderator

Damdifino wrote:

I've been having A/C anomalies this summer, which I thought I'd fixed. First, it tripped the breaker, so I cleaned the coils, changed the circuit breaker, and it ran good for a couple of weeks. But now, I turn it on and it just hums, like it's struggling to start up. What should I look at?


Not enough info.

Does it hum and no air blows?
Does it hum and air does blow?

Camreal

Kerrville, Tx

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Posted: 09/07/18 06:00am Link  |  Quote  |  Print  |  Notify Moderator

If you can get to the fan turn it by hand and if its not turning free the bearings need lubricating. Some times you can free them up with spray.

ksg5000

Oregon

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Posted: 09/07/18 06:08am Link  |  Quote  |  Print  |  Notify Moderator

Symptoms sound like low power or dead/dying compressor. Check your power source and make sure it's good and as others have said inspect your capacitors.


Kevin

wa8yxm

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Posted: 09/07/18 06:49am Link  |  Quote  |  Print  |  Notify Moderator

Two suspects..

First you said it "Just goes HUMMMM" does it blow air (Assumign not) spin the blower or fan (Remove top cover you should be able to spin the fan) Power off.

Does it spin freely,, or is it hard to turn

Hard to turn bearings sized up replace blower motor (if compressor works)

Spins freely replace start/run caps.

Same for compressor if it's not working replace start/run caps

You might also measure voltage to motors.. Make sure the blower is getting power control board issues (IE: Bad relay) can prevent the blower from blowing. (Same applies to the compressor from compressing). but odds are bearing failure or start/run cap failure

ALL TESTS except power measurement are POWER OFF (I mean trip the breaker manually (turn it off) power off. The voltage test have a partner turn the A/C on and off after you hook up the leads.


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Chris Bryant

Arden, North Carolina

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Posted: 09/07/18 11:58am Link  |  Quote  |  Print  |  Notify Moderator

It's because it doesn't know the words, obviously.

Seriously, the question asked, does it blow air? I would guess hum is compressor running and blower isn't starting, which would point to fan run capacitor (blower does not use a start capacitor), next bad motor.


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