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?

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.

Exactly what mine did when the start cap died.

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.

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?

Turn on my A/C and it just goes hummmm... | Good Sam Community

34 Replies

185EZ
Explorer
Oct 21, 2018
Glad you got it fixed
I had an electrical gremlin too and everyone walked me through it and got it fixed
Great bunch of guys here
Damdifino
Explorer
Oct 21, 2018
OP, with thanks. I really appreciate the coaching everyone's been giving me. Turned out to be more than the fan capacitor. I ended up replacing the fan motor and now it blows much better than ever. I learned a lot from this thread. HUGE THANKS!
hypoxia
Explorer
Oct 07, 2018
Damdifino wrote:
I have a MicroAir EasyStart installed.

That is for the compressor. The fan doesn't use the Micro Air. You need a run capacitor for the fan, IMHO. I think that has been mentioned a few times here.:h
PaulJ2
Explorer
Oct 07, 2018
No starting windings in the fan motor. The run cap electrically "shifts"position of the windings to give it a rotating kick to start,just like your hand.
That is how it works.
lostbytes
Explorer
Oct 05, 2018
It is the fan capacitor. When you push the fan to help it get going, you're actually using your hand in place of bad capacitor.
Get it now? The capacitor is only to engage the starting windings in the motor to help the main winding take over. Then, the starting winding stop cause the main winding is running it now. That's also the reason why you need more wattage at first to start ac till running watts are taking over. Same difference. Now, if you put another cap on and it still doesn't start the motor then, the starting winding in motor could be burnt. That's another process to diagnose. I have yet seen a bad starting winding so far. This is just an illustration of most motors. There are some that do not have starting winding but I will only confuse you more. Just know that your hand pushing the fan is doing the job when cap is bad.
3_tons
Explorer III
Oct 05, 2018
Damdifino wrote:
Okay, I'm finally on this again. I removed the top shroud and spun the fan. It turns freely, but there is a very slight roughness to it. Then I had my wife go inside and switch the A/C on. When I spun the fan by hand, it started turning and blowing air. We shut down and I waited several minutes to let the head pressure come down, but when I switched it on again it didn't spin.So I'm back where I started, except now I know the fan will run if I spin it by hand.

This may have been mentioned before, It could be the fan capacitor.
Damdifino
Explorer
Oct 04, 2018
Okay, I'm finally on this again. I removed the top shroud and spun the fan. It turns freely, but there is a very slight roughness to it. Then I had my wife go inside and switch the A/C on. When I spun the fan by hand, it started turning and blowing air. We shut down and I waited several minutes to let the head pressure come down, but when I switched it on again it didn't spin.So I'm back where I started, except now I know the fan will run if I spin it by hand.
tenbear
Explorer
Sep 13, 2018
That happened to me the other day. I gave the fan a little push and the fan took off. Everything has been ok since.
dougrainer
Nomad
Sep 12, 2018
Damdifino wrote:
dougrainer wrote:
MEXICOWANDERER wrote:
Remove inside fan shroud. You have to do the following using a LOT of care and concentration...

With the TIP of your finger, spin the fan blades ONCE to help get it started. Does the fan then start? Wait for yes or no cold air output if fan starts. I've had three A/C fans fail and all three had burned motor winding segments as well as a blown capacitor. Be suspicious of replacing the cap then a slow windup on the fans.

BEFORE you do this. Have NO Power to the AC and go on top and spin the fan blade. IF it spins freely, then do the above. But if it drags or sticks, the fan motor is BAD. No amount of bearing lube will fix it. Doug

Sorry to have to ask this...but do you mean the propeller fan or the squirrel cage fan?

They are on the same motor. Either one. Doug
Damdifino
Explorer
Sep 12, 2018
dougrainer wrote:
MEXICOWANDERER wrote:
Remove inside fan shroud. You have to do the following using a LOT of care and concentration...

With the TIP of your finger, spin the fan blades ONCE to help get it started. Does the fan then start? Wait for yes or no cold air output if fan starts. I've had three A/C fans fail and all three had burned motor winding segments as well as a blown capacitor. Be suspicious of replacing the cap then a slow windup on the fans.

BEFORE you do this. Have NO Power to the AC and go on top and spin the fan blade. IF it spins freely, then do the above. But if it drags or sticks, the fan motor is BAD. No amount of bearing lube will fix it. Doug

Sorry to have to ask this...but do you mean the propeller fan or the squirrel cage fan?