Strange AC behavior

[hertig]

A couple times now the AC fan started to 'sound strange' and did not blow at anywhere near its normal velocity. In both cases, I removed the grill over the intake, with no change in sound or operation. The first time, the filter was dirty and I cleaned it; the second time it was still clean. In both cases turning the AC off and leaving it off for a few hours before restarting restored normal operation.

Anybody have any idea what is going on and how to fix it?

 

[Poppa]

Strange AC behavior

Check the fan bearings for lubricant, some rquire a drop or two of oil a couple times a year

 

[Ed H.]

Strange AC behavior

Poppa's right on the mark. Also check both fan blades or blower wheels for excess dirt. If you're lucky, a few drops of oil and cleaning will take care of the problem. If not, you are probably looking at a new fan motor.

 

[Bush70]

Strange AC behavior

What year and make is the A/C. I know of three 2004 travel trailers that the fan sticks and you have to take the cover off and spin the fan. It is OK for a while but will stick again if you don't use it for a week or so. Sounds like a problem with this A/C. Maybe warranty

 

[Kirk]

Strange AC behavior

If the oil that Poppa suggests doesn't work you may have a problem with a start capacitor. They do fail, and can cause the fan to start slowly, or not at all. The sound part concerns me. Can you describe the sound that it makes? Have you checked the voltage when this happens? Does it happen anywhere you happen to stay, or might it be when you are at the same location? Very low voltage will cause the type of problem that you describe and it will damage the a/c unit if operated too long in that condition.

 

[Grandview Trailer Sa]

Strange AC behavior

I believe what Bush70 is talking about is bad motors. Dometic had a bad batch about a year ago and we have had to replace several motors. What happens is the armature has a "dead" spot on it. When the fan happens to stop and the brushes fall on the dead spot, the fan won't start again. It will create a humming noise. You can spin the fan and it will start when you are off the dead spot. It might be MANY starts before it hits it again, but then it might not. Dometic will replace the motor if you are in warranty.
This is not the orginial problem asked about though. I agree, the problem is either lubrication or low voltage.

 

[hertig]

Strange AC behavior

I'm not sure of the year or make, but I estimate it to be around 2000 and Coleman or one of their companies.

The 'sound' give an impression of the air being constricted, and the output from the vents is about 10% of normal air flow. My theory was that the coils were frosting up to the point air could not move through, and letting it set for a few hours let them melt clear.

No problems starting up the fan, and no noises which would point definitively at bearing problems, along with the rare occurance and 'self healing' nature of the problem. However, the lubrication idea is well worth checking out, since a significant slowing of the fan could produce the observed results.

It happened once in a pretty nice RV park, and once plugged into my house; pretty hot out both times. I didn't check the voltage but will do so 'next time' as I have a meter plugged into an outlet to allow this.

Do you have to get up on the roof and remove the cover to get at the fan (bearings), or can it be done from below (inside the trailer)?

 

[Grandview Trailer Sa]

Strange AC behavior

The biggest cause of an AC freezing up would be the setting of the temp. control. If you set the temp. in the 60's, and have the fan on low, you are asking for trouble. Almost everytime someone calls us with their AC frozen up, those are the two culprets.

 

[hertig]

Strange AC behavior

Looks like the coil was freezing up. Apparently a common problem here, when running on low fan. Thanks to all for the help.

 

[DL Rupper]

Strange AC behavior

I have found that low voltage is a real problem in older campgrounds. I bought a AUTOFORMER a few yers ago and it has fixed the low voltage problems so far.