Air Conditioning - Blower motor runs for hrs then slows down.

I've got a 9 year old, Heil 3.5 ton packaged ac unit. It can run for hours, and it cools pretty good, and then all of a sudden the blower will start slowing down and finally stop.

I went outside, removed the AC top, and felt the blower motor and it felt normal, not hot at all.

When the return suction and the input cold vent air starts getting weak, I cannot get the blower to start up strong again. I'll wait until the next morning and then it will work fine for a while.

This problems seems to be getting progressively worse.

Today, the return suction stopped working and there was very little cold air coming in through the vents, so I turned off the AC and opened up the AC top and felt the blower motor. It did not feel hot at all. I spun the motor fins by hand, and it seemed to spin fairly easily.

I then put the top back on, and turned on the AC, (not more than about fifteen minutes after the blower had stopped) and it worked great, with full blower cold air, and full blower return, for a few cold hours, and then both the return and the incoming cold vent air started getting weak again until I could barely feel any cold air coming out of the vents, and it wasn't sucking any air into the return.

Could the blower motor be going bad even though the motor did not seem overheated? Could it be the capacitor going bad?

Any ideas about what I should test or replace first?

Thanks!

Hmmmm!? I might have answered my own question.

My blower motor is a Permanent Split Capacitor Motor (PSC), in which, if I understand what I've just read, the "run" capacitor is not used to start the blower motor, but to help assist the motor in continuous running. In other words, the capacitor acts as part of the blower motor.

Thus...... if the run capacitor is going bad, perhaps it is not doing it's job in keeping the blower motor running. When I spin the blades on the blower, the motor seems to spin OK ( as much as a novice like me can tell ).

Does this make sense to those with the know?

I am going to replace the run capacitor first, and go from there.

I take it that this is the inside blower motor. Dont run the unit with out it. What happens if you just turn the fan to fan on?

ED ;)

I have seen units that have a frozen evap coil that exhibit the same symptons did you happen to eyeball the evap coil when you had the cover off just to be sure it was not iced over??????

I take it that this is the inside blower motor. Dont run the unit with out it. What happens if you just turn the fan to fan on?

ED ;)

It's a packaged unit, for a mobile home, so it's all contained outside.

I had the same problem with the blower fan when I switched the fan from "auto" to "on".

I had read your advice, in earlier posts, about not running the unit without the blower fan working, so I kept the AC off yesterday. Thanks for the advice!

I picked up a 10mfd, 370 volt run capacitor and put the little sucker in the AC and it is running perfectly! :thumbup:

DoItYourself.com is a valuable resource. I'm glad that I found it!

Have a nice day, and thanks for your advice.

I have seen units that have a frozen evap coil that exhibit the same symptons did you happen to eyeball the evap coil when you had the cover off just to be sure it was not iced over??????

There was no ice on the evaporator coil, but thanks for reminding me to check for that.

The new $7 capacitor is doing it's job and the unit is running like new. It actually cost me more for the gas that my truck used, driving to get the part, than for the capacitor!

Thanks. Have a nice day!

I have seen units that have a frozen evap coil that exhibit the same symptons did you happen to eyeball the evap coil when you had the cover off just to be sure it was not iced over??????

It appears that you were right.

The bottom part of the evaporator coil was iced. I didn't notice it. Perhaps there was more icing than was visible from the outside, I don't know.

The flex duct under the mobile home is narrowed in several places. I need to get that problem resolved.

Now that I have replaced the blower capacitor and removed the heat strip, the input cold air is working fine, but the return gets weaker and weaker as the evaporator coil freezes up because of the incorrectly installed flex ducts.

Thanks.

I still think you could be low on freon there. Could have contaminated the freon Or noncondensables in there. If some one worked on it.

ED ;)

I still think you could be low on freon there. Could have contaminated the freon Or noncondensables in there. If some one worked on it.

ED ;)

Thanks for the info. I also wonder if the system could be low on freon.

I've been running the system on about 77 degrees. As long as I don't turn the temperature any lower, the evaporator coil doesn't freeze up. It runs all day, albeit a little warm.

I found some more problems with the unit. The flex ducts are reversed. The 14" is on the cold side and the 12" is on the return side. Plus....... both flex ducts are compressed in a couple of tight spots.

I am going to see if I can remedy the compressed areas in the flex ducts and then see if the AC runs better, even with the flex ducts installed incorrectly.

Thanks again for taking the time to respond to my post!