Community Forums

**CountryFit** · 01-31-2023, 10:16 PM

Hi everyone,
Having an issue with the front Duo-Therm a/c - since last week, the fan motor hasn't run, no air coming out of vents in heat pump mode though a whining sound could be heard when it's called for.

My first thought was capacitors. Today I opened the unit up and saw 3 capacitors - the run cap, the start cap and the PTC cap, but none of them seems deformed or bulged. Do you see anything wrong on the pics, or should I look at something else? Appreciate your comments.

**CountryFit** · 01-31-2023, 10:38 PM

Thinking to replace the start cap with a heavier duty one like this.

153stars · 02-01-2023, 05:38 AM

Failed caps don't often deform. Have you to tried to spin the fan by hand. Not unheard of mud daubers building mud nest and jamming up blades. Fan only has only a run cap.Could be bad bearings or fan as well.

TXiceman · 02-01-2023, 06:21 AM

With a 23 year old coach and possibly A/C HP unit, it may just be time to replace the unit. Have you gone up to top with a volt Ohm meter to check that you are getting power to the fan motor and compressor?

You will need to do a little trouble shooting to find the root cause. Visual inspection of the components will have a limited use on finding the problem.

Ken

Ken

Domo · 02-01-2023, 07:24 AM

Could be the center of the fan hub has deteriorated and the shaft is simply spinning - thus making a whining sound.

I think I'd pull the cover and see what's whining before changing capacitors or thinking about "upgrading" them based on physical appearance (?) when the originals had lasted 23 years (we assume).

98fleetwood · 02-01-2023, 07:30 AM

Both my acts made whining noise when I first got my rv. No air coming out. I pulled the covers and unstuck the fans. Simply turned them. I could feel them break free. That was 2 years ago. They have worked fine ever since..
Good luck

jacwjames · 02-01-2023, 08:04 AM

Back in 2015 my front AC started to kick the breaker. I started to monitor the EMS amp load panel and saw it was pulling really high amps at startup. Pulled the top of the AC unit and tried to turn the motor, I could barely rotate it with my hand. So I replaced the motor and that fixed the problem.
So check your motor.

Fast Forward last year, my wife said the rear unit was starting to make a loud noise, checked it, motor was fine but the isolation bushings that supported the motor were bad, fan would still run but at time it would hit the metal,>>> another thing to check

But when I was checking on parts there weren't any available for my vintage AC's 2002 model Dometic. So I just bit the bullet and replaced both of them even though my old ones were still running. Bought bought new 15K BTU high capacity Dometic heat pumps and a Microair thermostat for ~$3K.

New units like I bought went from ~$1200 to ~$2000 now. YIKES

**CountryFit** · 02-01-2023, 10:44 AM

Thank you all for the invaluable information, which opened up new angles for me to look at it.

Yesterday I removed the cover, and manually span the fan blades. It was not free spin but spin, much heavier than what I expected. Yes, 23 years old, the bearings could have been out, or very dry. I'll try to lube them and see. Will make sure the power is present to the motor, and pin down where the whining noise comes from.

Have ordered the start capacitor for $8 including shipping, arriving this Friday.

I'll work on this and keep you posted.

Best regards to all!

shootist · 02-01-2023, 08:08 PM

The cases sagged on mine, had to shim the motor to get the fan back in the center of its condenser hole. Made a clanging noise.

**CountryFit** · 02-01-2023, 10:35 PM

Quote:

Originally Posted by shootist

The cases sagged on mine, had to shim the motor to get the fan back in the center of its condenser hole. Made a clanging noise.

I'll check it when I have access to it in this weekend.

hypoxia · 02-02-2023, 06:24 AM

It's time to acquire a meter that measures capacitance. The connections also need to be cleaned. If you use Chinese capacitors prepare for a short life, they fail frequently and are frequently out of tolerance when new.

**CountryFit** · 02-02-2023, 10:46 AM

Quote:

Originally Posted by hypoxia

It's time to acquire a meter that measures capacitance. The connections also need to be cleaned. If you use Chinese capacitors prepare for a short life, they fail frequently and are frequently out of tolerance when new.

When I receive the new capacitor, I‘ll clean the contacts well and test it with the new capacitor installed. Cross fingers

Domo · 02-02-2023, 08:58 PM

You mentioned "front A/C" which led me to believe you might have two that are the same...

Why not switch parts with the good one - assuming they are the same.

**CountryFit** · 02-02-2023, 10:44 PM

Quote:

Originally Posted by Domo

You mentioned "front A/C" which led me to believe you might have two that are the same...

Why not switch parts with the good one - assuming they are the same.

You are correct, there are two identical Duo-Therm a/c's on the roof. The bed room a/c is good. Good idea, I can swap the capacitors and see.
Two brains are better than one

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