A/C condenser fan motor hot...is this normal?

[ezriderga]

Was finishing up my yard work today and when the condenser unit kicked in I noticed the fan motor sounded a little unusual. After putting my mower up, I walked over to the unit to check it out.

When I laid my hand on top of the unit it felt hot to the touch. I wondered if this is normal or is this a sign the fan motor is on it's way to failure. I turned the unit off and checked the fan and it seemed to turn OK.

Should I be concerned about this or just let it continue to run and keep an eye on it? Or is this a sign that something else may be bad or going bad? Thanks for your input.

 

[lzenglish]

In terms of hot, you should be able to hold your hand on the motor without getting burned, or without having to let it go, because of the excessive heat. If this is an oilable motor, oil it. If not, write down the specs. on it, and get prepaired for the worst case senario, like a change out. Most of these motors have a bi-metal heat overload switch imbedded in the windings, but some do not. I would put a clamp on amp probe on it, and see if it is within its amp draw specs., as well. Are you sure the noise you heard was not the compressor itself?

Wayne

 

[ezriderga]

I suppose it could have been the compressor Wayne. I just assumed it was the fan motor since it was so hot I could not lay my hand on it.

Do you know what the amp draw should be? I'll look and see if I can find my amp clamp.

 

[pipsters]

The motor should have a placard on it showing amp draw.

I don't like to replace working items but if it really is getting that hot, I'd see what it's drawing as far as amps and even still if normal I would seriously consider replacing it before it breaks. Buy a new motor and a cap ($20) and you won't have to worry about it. If the motor stops and the compressor is running it gets hot and will shut off due to overheat. Bad for everything involved. Plus a pain if it happens at 2 am on a 82F night.

 

[pop pop]

Recently heard mine as I walked by. It was an obvious bearing noise. Removed the motor, disassembled and found it to be "oilite" type bearings with a media to hold the oil. It was dry, so I added light oil and have heard nothing since. If the bearings are adding load to the motor, it might be hotter than normal. Mine was a 30 min job.

 

[nehog]

To be technical, there should be a label or tag on the motor. One specification will typically be temperature rise. Temperature rise is the increase above ambient temperature that the motor can (will) get while in use. Some motors that temperature rise is rather high, typically 70 degrees Celsius. To properly measure the motor's temperature, I'd recommend a flat surface temperature measurement tool, though you may have success with an infrared unit.

 

[ezriderga]

I checked the plate on the motor thru the grille and it appeared to read amps...1.79. I put my amp clamp on the lead going to the motor and it read .3 amps. Does this sound normal?

The motor is still hot to the touch, but it keeps running and hasn't caused any known problems. I suppose I'll just keep running it and check it periodically. Any other suggestions? Would you go ahead and change out the motor?

 

[lzenglish]

I checked the plate on the motor thru the grille and it appeared to read amps...1.79. I put my amp clamp on the lead going to the motor and it read .3 amps. Does this sound normal?

The motor is still hot to the touch, but it keeps running and hasn't caused any known problems. I suppose I'll just keep running it and check it periodically. Any other suggestions? Would you go ahead and change out the motor?

That amp reading sounds good to me. I don't know exactly why it is running hot, but here is what I would do. Make sure the condenser is clean, make sure the fan motor is clean, and running in the correct rotation, and the bearings are free. Keep in mind, that if it fails, it will overload the compressor, and either trip the service disconnect fuses, and or main breaker, so you are protected in that respect. Even before that, the cond. fan motor shoud have an internal overload switch inside it. If you are still concerned, I would research, and line up a replacement motor for it, so, just in case it fails, you can get your hands on one quickly. Or, just change it out for piece of mind, as was mentioned. I'm very surprised the internal cond. motor overload has not tripped yet, since it is as hot as you say it is?

Wayne

 

[coolreed]

Alot of times when a Condesor Motor becomes hot the Starting Capacitor has gone bad.
The starting caps tend to break down in the summer. They are electrolytic capacitors and they just go bad. You can tell they are bad because they swell up on the ends.
The motor gets hot because the current required to start up is so high. The start capacitor will go bad gradually. If you do not replace it (if that is the issue) you will burn up the motor.

Good Luck

 

[coolreed]

Sorry,..I fat fingered the first sentence. Strike the Condesor. Doh!

 

[nehog]

I checked the plate on the motor thru the grille and it appeared to read amps...1.79. I put my amp clamp on the lead going to the motor and it read .3 amps. Does this sound normal?

The motor is still hot to the touch, but it keeps running and hasn't caused any known problems. I suppose I'll just keep running it and check it periodically. Any other suggestions? Would you go ahead and change out the motor?

1. Depends on the meter. Some meters don't read low amperage currents well.

2. How hot is hot. A rule of thumb... How long can you hold you hand on the motor (uh, not while running, but immediately after disconnecting the power!) Just don't burn yourself. If you can leave your hand on it for a short while (10-15 seconds, perhaps) then likely it is not too hot. However, the accuracy of touch temperature measurements is, at best, rough.

3. Smell... One of the best tools to measure temperature if you don't have a thermometer is your nose! As a motor reaches maximum design temperature (which is usually the insulation on the windings limited) you will smell it (the insulation getting too hot.) A sniff test (again, disconnect power before getting your nose or any other part of your body near that motor!) can help. A clearly pungent smell signifies that the insulation is breaking down, and the motor has failed.

 

[ezriderga]

Thanks for your replies. It's good to know there is some overload/overheating protection built in to the motor and related parts.

I had to replace the start cap several years ago. I had not thought to check that, but I will.

I initially stated the motor was getting too hot to touch. To clarify that, you cannot lay your hand on the motor end and leave it. It is hot enough you will immediately lift your hand. Have not noticed and burning type smells.

I think I will check the start cap next and possibly go ahead and line up another fan motor just in case it goes out. Thanks again for your help.