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Tom
Tom, HVAC Technician
Category: HVAC
Satisfied Customers: 770
Experience:  16+yrs HVAC/R service. Residential Commerical Industrial
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The blower in my trane unit wont come on. The air conditioning

Customer Question

The blower in my trane unit won't come on. The air conditioning unit works fine and the relay switch also seems to work (I hear a humming sound coming from the unit when it's depressed) but the fan itself doesn't run. The indicator light flashed steadily and continuously, which according to the diagram means that the unit is working properly.
Submitted: 3 years ago.
Category: HVAC
Expert:  Tom replied 3 years ago.

Tom :

Sorry you're having trouble....

Tom :

Is your blower variable speed or just a standard blower ?

Customer:

it's an old unit, so I believe that it's standard.

Tom :

Will it run if you switch it to fan 'on' instead of auto?

Customer:

no- no change.

Tom :

If you switch the heat on will the blower start?

Tom :

You may have a bad fan motor....or you could have a relay issue on the control board

Tom :

if it's a relay...often times switching it to fan on will get it going in a different speed..

Customer:

no, the heater ignites, but the fan still doesnt start.

Tom :

That's not good.....

Tom :

It could be a bad run capacitor.....or it could have a worn motor bearing that won't let it start.

Customer:

switching to fan "on" also doesnt get it to start.

Tom :

If the bearing is bad....the fan will still spin freely with power off (usually)....but when power is applied it will lock up and hum......the extra clearance in a worn bearing will allow the rotating part of the motor to lock ...

Tom :

(due to magnetic pull from the winding).

Customer:

i read online an account of one owner who took the capacitor apart and found that a fuse had come loose. replacing the fuse fixed the problem.

Tom :

There is nothing to take apart in a capacitor

Tom :

The run capacitor could be bad though.......if it's open or shorted..the motor won't start

Customer:

how would i know if this is the case?

Tom :

If you inspect the capacitor....any sign of bulging around the electrical terminals or signs of oil leaking would indicate it's bad

Tom :

Don't touch the wires on the capacitor though....if it's good there could still be a charge in it..

Customer:

i don't see anything like that.

Tom :

There is a test you can try for the motor bearing too..if you're super careful

Customer:

ok

Tom :

Does your furnace have a door switch?

Customer:

yes

Tom :

ok....if you push in the door switch now...will it hum?

Customer:

yes

Tom :

ok....let it out....(power off)......reach in and give the blower as good of a spin as you can and try to hit the door switch while it's still spinning.......

Tom :

if it seizes up you likely have a bad bearing

Tom :

did that make sense?

Customer:

yes. im just thinking of how to get my hand in there to spin it. it's a tight space. let me try.

Tom :

be careful......if it's not going to work..better to remove it from the furnace and check it

Customer:

it worked!

Tom :

What worked?

Customer:

I'm assuming that if it was going to seize up it would do it immediately, right?

Tom :

yes

Tom :

you mean it's running?

Customer:

spinning the fan and then depressing the door switch.. The fan kicked in and started running.

Tom :

I wasn't counting on that...

Tom :

It probably won't restart...I'm guessing..

Tom :

So...back to the original problem...

Tom :

Probably a bad bearing...(maybe it turned hard or no?)

Tom :

OR could still be a bad capacitor...sometimes they'll start if you help them...does it seem to be running full speed or a little slow?

Customer:

meaning, if I turn it off, it won't restart again? it seems to be running normally.

Tom :

It may or may not....problem being...we didn't really 'fix' anything.

Tom :

I've seen cases where the bearings are getting dry...and after the motor runs awhile and gets hot..it will slow down and stop..

Tom :

Trouble is I"m not there so I'm doing a little speculation..

Tom :

The good news is ..seems like your control board is functioning ok....

Customer:

i'll admit, the air filter was really dirty. could that be a problem? and how could I lubricate the bearings?

Tom :

Most newer motors do not have an oil port....

Customer:

it's at least 6 or 7 years old.

Tom :

IF you pull the blower out and disassemble the motor...you can oil them from the inside..but if you've never done that...I really don't recommend it....

Customer:

yeah, no kidding.

Tom :

At only 7 ...bearings shouldn't be gone..

Tom :

I'm still a little suspicious of the capacitor...

Tom :

I'd ask you to stop it and start it again...but I'm guessing you want cooling

Customer:

yeah, i'll take functional for now. is the "manual spin and push the button" trick likely to work if it won't restart again?

Tom :

since it did once...probably....

Tom :

We know your controls seem to be ok..which is good.....

Tom :

the next time it acts up or when you have time to play with it.....I would concentrate my attention on the motor / capacitor..

Tom :

Capacitors are cheap...less than $20.....

Customer:

yeah, but the labor for a professional installation is expensive. how easy is it to do myself?

Tom :

Not terrible....sometimes the wiring colors are a little different if you don't get an exact replacement motor...

Tom :

but other wise pretty much nuts and bolts..if you're mechanically inclined at all

Customer:

is there a website with instructions?

Tom :

hmmmm don't know..I've never looked for one...could google it...it would not surprise me

Tom :

Here is what you're looking for the next time you shut it off..

Tom :

See if the blower spins really free...or if it takes a little effort to spin....

Tom :

did the motor make any noise like it was laboring to come up to speed?

Customer:

spins freely and didn't seem to be struggling to come up to speed.

Tom :

I dont' know what else to tell you tonite. I'd run it and get the house cooled down.

Customer:

awesome. Thanks for your help!

Tom :

If it stops again....try starting it...if it works again by spinning it...replace the capacitor.

Customer:

got it.

Tom :

You're welcome to reply back here if you have more questions...I'm in and out...but I'll reply when I can.

Customer:

great. thanks again!

Tom, HVAC Technician
Category: HVAC
Satisfied Customers: 770
Experience: 16+yrs HVAC/R service. Residential Commerical Industrial
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