Fan motor gets hot then stops

[larrylwill]

Mini Split Fan overheating

I have an off brand Mini Split heat pump. 18,000 btu its a BonAir. I installed it myself. I have had it 9 years. Other than having to have Freon added once due to a fitting working loose., its been running fine, although very loud inside fan. Yesterday I was running the air condition and I noticed the fan sounded quieter than usual. I had previously removed the bottom vanes which caused a lot of noise. I checked the speeds and they all worked properly, high was as usual noisy.
I let it run and after a couple of hours it stopped blowing air. I checked the fan and the motor was very hot. I let it set over night and this morning I checked connections and voltages, although I have no Idea what the voltages should be on the 4 wires to gnd. Anyway it ran fine but the motor was again hot and again after a couple hours it shut down. I guess thermal overload. I checked th 2 uf cap and it reads 1.5uf both ways. The motor shows 2 wires to the cap and 3 windings.

How can I find out if the motor is bad without replacing it first? Does anyone know what the voltages should be or the winding resistances.

 

[kd3pc]

since you can not fix it, the fact that the fan is bad - is largely irrelevant.

Replace it, and be done.

I would not be inclined to remove vanes on the new one, as they are designed to be there for a reason.

 

[larrylwill]

The Vanes are on the plastic cover where the air comes out, not the motor and they are there to disperse the out air in different directions, but they also impede the air flow and make the air flow louder and restricted. I cant see how removing air restrictions affected the fan on a 2008 heat pump inside blower motor. Yes I would replace it if and when I find a replacement for a brand that is gone.
FYI there are several things that can make the motor overheat, bad cap, wrong voltages on the coils, binding on the shaft air restrictions. I know its not 1 3 and 4 but do not know if the voltages on the fan out of the board are correct. If I could find the resistance of the winding's I could know for sure if its the motor, or I could spend a couple hundred on a new motor if I could find one and prey its the problem. Just replacing things without knowing is shotgun repair. If that don't fix it, then replace the circuit board, if that don't fix it then replace the bearings on the fan.

 

[justinjoyal]

Did you ever clean the blower ?

 

[larrylwill]

I forgot to say in my original post. I blew out the fan and behind the coils, lot of dust. I also cleaned the fins. Here's the schematic of the motor. I did find one. Cost $179 + shipping.

 

[naturalgas]

Nine yrs old, replace motor it's worn out


Sent from my iPad using Tapatalk

 

[handyman85]

The capacitor also will have a tolerance +/- 10% or something like that. At 2uf, 1.5uf is 25% under rating which might be outside the bounds.

The changing of sound of the motor usually isn't a good thing. If you pull/wiggle the shaft end away from the body, there should be no movement. If the shaft can move in and out the motor is bad.

You can also measure the internal resistance of the windings to ground, all legs should relatively close to one another

Hope this helps

 

[acmikee]

can you even get parts on a 9 year old unit

 

[metlmunchr]

FWIW, removing air restrictions will increase the load on a fan's motor rather than decrease it as the OP seems to believe.

The fans used in small units are either propeller type or forward curved centrifugal type. They are not positive displacement devices like piston pumps that overload due to pressure buildup if a valve is shut off, but rather devices whose load depends on the mass (weight) of the air they are moving at any particular time. Put an amprobe on the motor and block off the air discharge and watch what happens. The load will go down rather than up. Conversely, removing any sort of designed-in restrictions will cause the fan to handle more air and the load on the motor to increase.

That said, removing a few of the vanes on the discharge probably doesn't increase the air quantity enough to make much difference on the motor load. From what I've seen, most of these small motors that turn themselves into heaters over time either have tight bearings which are obvious if the fan won't spin freely with the power removed, or their thrust bearings are shot, which is evidenced by end play in the motor shaft.

 

[larrylwill]

As to the cap. Easy enough to change and it was tested with a multimeter and who knows how accurate that is on caps. As to find the part. I found the motor at a manufacture only and its $180 + shipping which will make it > $200. Its a 230v 3 speed motor. 3 speed 110v ones the same size are $20-$30. The fan is a long 3ft squirrel cage type one.

My quandary is its almost 10 years old. Its a seer 13, its noisy. I use it in my office/shop. I test ICs for a German company. Putting $200 in a motor the may not even be the problem vrs buying a new seer 16, 35db one on low I can get for $800 shipped. I will check today if there is 110v on the circuit board and buy a 110V one for $25. If thet works Im good if it doesnt I may hust buy the new seer 16 one.

 

[larrylwill]

I found a new 3 speed 115v motor that fits for $20 sipped. I found a way to run it off 115v. Most do use 115v but this one was from Canada. I also checked the operation of the relays that control speed.

 

[justinjoyal]

I found a new 3 speed 115v motor that fits for $20 sipped. I found a way to run it off 115v. Most do use 115v but this one was from Canada. I also checked the operation of the relays that control speed.

How will you get 115v to the motor if your unit runs off 240v ?

 

[larrylwill]

Many appliances run on 220v but 220 is 2 x 110v with a common ground. i just moved one side of the motor winding to 110v. The other side of the wingdings get grounded for the 3 speeds..

 

[48RON54]

there are plenty of how to videos regarding this topic on youtube. I dealt with this last summer on a blower motor. I can't remember the exact search I used but I'm sure it was something along the lines of "how to test blower motor" though I would think your search might be a little different. I'm not familiar with heat pumps though so maybe the same search I used would still help you. You are going to need a meter... I had to remove my motor to test it. Be prepared to be bored to death by those videos though.

That having been said, I would just replace it. that's a lot of troubleshooting for a motor that is pretty obviously bad.

 

[larrylwill]

Well I checked the amp draw of all wingdings as well as the resistance. At 220v the most is 165 ma which is 36 watts, the motor is rated 50 watts. The motor still gets hot enough you cant hold your finger n it at any speed. I also tried a new cap although larger. 5uf. Same problem. The one on it is 2uf +/-10% which is 1/2 uf so 1.5uf is within tolerance.

Next I ordered a new 110v 3 speed motor. Even on the bench it will burn your finger at low speed and no load. I checked the amps of it and its about 38 watts also.

I do not understand why these motors run so hot. There is no cooling fins on either of them. Although I never felt how hot it ran before I removed the case due to thermal shutdown.

I do not think the motor is bad because if it is than the new one is also bad.
The 220v one gets 220v to the common and through a relay a winding gets grounded.

The 110v one I tried on the air con with 110v to common and grounded the other side through the relays, same problem. Then I ran both on the bench, same problem.

The only way I can cool them down is with a hefty fan.