How to test this fan motor?

[Tracs]

I have a thread in the Heating and A/C section about my Perfect Aire Mini Split ductless a/c heat pump.

https://www.garagejournal.com/forum/showthread.php?t=413251

Snow caused the condenser fan blade to become frozen in a block of ice. I thought all was good when I thawed it, but things are not good. The day I thawed it the motor was spinning the fan blade.

But now that I tried to use the A/C the fan isn't moving a fraction of a inch.

My uncle is a HVAC installer and he originally thought it was the motor's 2.5 uF +/-5% 450V capacitor.

I got a good multimeter and the capacitor tests at 2.47 uF. So it seems fine.

So when I disconnect the plug from the board (Black, Yellow, Red) how do I apply power to test?

I have a 120V AC power supply. I don't have 240V like the fan is, but will the 120V be enough to spin the fan even slowly to let me know if the fan is good or bad?

 

[Mr. T]

So when I disconnect the plug from the board (Black, Yellow, Red) how do I apply power to test?

Plug it back in?

If you have a good cap and power at the connector there is a decent chance your motor is shot.

 

[Tracs]

Plug it back in?

If you have a good cap and power at the connector there is a decent chance your motor is shot.

I just did a test for power at the board's connector. Across the Black and Yellow it showed 135V. Which would indicate the unit is calling for Low Speed. Fan doesn't even hum or turn.

I wanted to test the motor to rule out a main board problem.

 

[Mr. T]

Can you look up the installation manual? Sometimes there are test jumper pins you can use.

I’m not familiar with your system (or most HVAC systems for that matter). I’m just a general machine troubleshooter.

But my general experience with motors would make me think that if you have power and a good cap the motor might be dead. Does it make a difference if you manually give it a push to get going (in the direction of rotation)?

I’m hesitant to recommend another power source available to an average homeowner if you can’t put some reasonable over current protection (small fuse etc.) inline just incase.

 

[Tracs]

Can you look up the installation manual? Sometimes there are test jumper pins you can use.

I’m not familiar with your system (or most HVAC systems for that matter). I’m just a general machine troubleshooter.

But my general experience with motors would make me think that if you have power and a good cap the motor might be dead. Does it make a difference if you manually give it a push to get going (in the direction of rotation)?

I’m hesitant to recommend another power source available to an average homeowner if you can’t put some reasonable over current protection (small fuse etc.) inline just incase.

The installation and user manuals give no details on troubleshooting or diagrams.

I did try to spin the blade in direction of travel. Nothing.

Another source of power available.......eh?........ You mean like a 240V welding extension cord?

Well I just tried that too. Jumper leads into the plug and probed the disconnected fan connector. Nothing. Touched one lead to Black and then brushed against Yellow then Red. The leads didn't even make a spark on the connector. I would think the fan motor is dead.

My cousin who is a electrician is going to come over tomorrow or Friday and properly test the motor and tell me if it is good or bad.

 

[wyliesdiesels]

Have you tried testing the resistance of the windings?

 

[Tracs]

Have you tried testing the resistance of the windings?

I did briefly try too. The meter was on auto range and from Black to Yellow showed something like 1.100 M OHM? I could be wrong. Then again I didn't look to carefully because I didn't know what I should be looking for.

 

[Tracs]

I just went out again.

Black to red has 1.6 M ohm and slowly climbs
Black to yellow has 9.8 M ohm and slowly climbs
Red to fan motor case shows 26.5 M ohms and slowly climbs
Black to fan motor case shows no reading
Yellow to fan motor case shows no reading

This is with the capacitor disconnected

 

[wyliesdiesels]

yeah you have failed windings. the resistance shouldnt be that high

 

[grounded-b]

I just did a test for power at the board's connector. Across the Black and Yellow it showed 135V. Which would indicate the unit is calling for Low Speed. Fan doesn't even hum or turn.

I wanted to test the motor to rule out a main board problem.

If it only reads 135V from the Yellow to the Black, there is a problem with the circuit board. The motor needs 240V. It would not develop enough torque at 135V to start.

240V is applied to Black-Yellow for low speed. 240V is applied to Black-Red for high speed.

Steve
JW

 

[Tracs]

If it only reads 135V from the Yellow to the Black, there is a problem with the circuit board. The motor needs 240V. It would not develop enough torque at 135V to start.

240V is applied to Black-Yellow for low speed. 240V is applied to Black-Red for high speed.

Steve
JW

Hmmm. That might be a big problem then. I hope the wholesaler can get me the service manual so we can check this out. I wish they would just authorize a complete unit swap.

 

[Tracs]

If it only reads 135V from the Yellow to the Black, there is a problem with the circuit board. The motor needs 240V. It would not develop enough torque at 135V to start.

240V is applied to Black-Yellow for low speed. 240V is applied to Black-Red for high speed.

Steve
JW

So I went out and did a more detailed test.

Upon start up it was 135V across the Black and Yellow, low speed.

Across YEL & RED I got 240V.

After a few minutes when the coil warmed up I got 240V across BLK & YEL.

After 10 minutes the voltage dropped off BLK & YEL and across the Black and Red I got 240V. High speed.

So without a service manual and little understanding of how Mini Split's operate, it seems that the circuit board is OK.

 

[Tracs]

Got a new motor and pried this one apart.

It was defiantly burnt up.

 

[dogdog]

...........LOL and you didn't see that before ?

 

[Tracs]

...........LOL and you didn't see that before ?

Not on a totally enclosed motor that I had to grind the rivets off to open......

 

[pancho400cid]

Well... the new motor wasn't premature.

 

[Movover]

Not on a totally enclosed motor that I had to grind the rivets off to open......

I would think you could smell it through the case. WOW that is toast!

 

[Dagny]

I'm in the business. YOU are going to see why I hate mini's. the parts are very high priced and are oem only. I will only sell one when there is no way to make a regular system work.

 

[wyliesdiesels]

I would think you could smell it through the case. WOW that is toast!

bingo

ive smelled burnt out canopy and wall pack lights just by taking the top cover off without seeing any ballast components...