Attic Fan Diagnosis

[jatoxico]

So my attic fan croaked. It may have tried run while fan blades were jammed from insulation. Has power and the thermostatic switch is working (can turn on and off a test light with it).

Unit has an external capacitor which is feed with two wires that first pass through the fan. I removed the capacitor. With thermo switch set to provide power to fan, should power be present at the wires that supply power to the capacitor?

I think it should and the test light should come on but not 100% sure. Trying to determine if the fan or just the capacitor is shot.

 

[jatoxico]

FYI and on the hope this may help someone else, this is a Home Depot fan made by Master Flow. There is an 800 number right on the fan and after calling, it has a 10 yr warranty (surprise) that they will honor (double surprise).

Just have to figure out exactly what I need to replace. They will send what I want but easier to replace the capacitor than whole motor.

 

[heat seeker]

Unless you're sure, I'd go with the entire motor, even though it's more work. From your description, it sounds like there's a wiring problem inside the motor.

 

[jatoxico]

Yes kinda settled on that after thinking it through and speaking with a friend. I really don't have a good way to test the capacitor and it's mounted to the motor anyway. Hopefully they'll send the entire unit with housing and save me some time in a hot attic.

 

[heat seeker]

Hope they do! Good luck!

 

[Bristlecone]

The few failed capacitors I've delt with have been swollen or bulging. To test it you need a multimeter. A test light is no use. Label the wires so you can reattach them properly. Remove the 3 wires. Set function on multimeter to 200 or more volts A/C. Put black probe to ground and red probe to each of the 3 terminals of the capacitor. One at a time. If you read no volts then you can touch the terminals without getting a shock. The capacitor stores energy. Most likely it will have none, but you have to check. Now, set multimeter to the "continuity function" (so it will beep when touch the red and black probes together. You will be measuring resistance ( ohms). Choose two terminals to check. Put red probe on one and black probe on the other while watching meter reading. Reverse the probes. Move to the lone terminal and check the same way. What you're looking for with these terminal testing combinations is for the multimeter display to zoom to a high number and drop off to nothing.

 

[fbelec]

if it's a quality motor company they will ship the new cap with the motor. sometimes they give you the same physical size motor with same horsepower but ratings are different. if it needs a cap the motor name plate should say what size cap to use. if the motor is humming but not turning but turns when the power is shut off it may need just a cap. they are cheap. the cap is usually wired on the neutral side so volt meter to ground might be zero. if power is on and the motor is doing nothing it's junk. for future reference some of those motors have oil holes. oil it yearly or bi yearly and it should last a long time. and don't try to cool the attic down to 70 it will work to hard and get burned out set the temp to 100 or 110 and it will do it's job. some people think that temp is to high. to are the people that replace the fan every other year during the summer your attic will run between 130 and 150. i've burnt my are on many a air conditioning units

 

[greg13]

If they are willing to pay for the whole shot, take advantage of it and make the unit new again.

 

[jatoxico]

They sent new motor including capacitor. Swapped it out and back in business.