A/C Fan Motor Noise

[MidNiteFury01]

Howdy folks, 01 Vette. A/C fan motor works just fine for about an hour on a specific speed, then air stops blowing. I push up a couple of times on the switch and blows good for about 20 minutes, repeat, and push to max, does well for about 10 minutes. I shut the A/C off for about 5 - 10 minutes, turn back it on and the fan works great, but for not as long. It makes a ticking noise when its about to go out. Air is always cold, just not a lot of force.

 

Nothing in there as I pulled the motor. Ran it off a battery for about 20 minutes, ran just fine. When I shrouded the fan a bit to feel it pull the air, it started making the noise. Not sure if its the motor or the blower motor control module or if its the evap icing over and not allowing flow or what. I took apart the control module and it doesn't show any signs of burnt tracing or circuits. It sure does drip a lot of condensate onto the drive way when I'm finished driving it. 

 

Any help is greatly appreciated. 

[TheCMSH]

Throwing any codes?

[MidNiteFury01]

No codes. No debris that I can see, just a little bit of dust. Had it leak tested by a reputable shop, they had it for a week, no leaks found. 

[TheCMSH]

I've chased fan motor noise on a few different vehicles, seems like its always a tough one to chase until they absolutely crap out and howl 100% of the time.  My experience if you think its the blower motor, it probably is the blower motor.  I chased gremlins in the control switching before circuits before, replaced components, and it still ended up being the blower motor

 

When you mentioned the clicking I thought maybe blend doors, but as I recall those should throw a code if they aren't functioning property.  Short of pulling the HVAC fuses (18 & 27 as I recall) which will result in re-indexing of the blend doors, I don't know what tree to send you up exactly.  Hopefully the bigger brains will chime in here

[Two Fangs]

When you were shrouding the fan, was it still running off the battery?  If so, that likely removes the control module from the equation.The ticking noise is not too uncommon, usually the brushes smacking the commutator segments, I'd lay odds on the motor itself beginning to wet the bed, as long as there is nothing in the airbox that the fan is hitting.

[MidNiteFury01]

The fan was still running off the battery. I suspect I was simulating a load / flow restriction and thus causing the fan to replicate the noise. Its interesting that it would run at the appropriate speed, then slow. Then when I bumped up the speed, it would speed up, then slow down again, and make a rattle/ ticking noise. Would the motor just get too hot and give up, then when I shut the A/C off for a bit, allow it to cool, it would then work normally?

 

I suspect you are right about the module, it is clean (no arcing, burnt circuit) although I broke it trying to take it apart (stupid move).

 

THANKS for the guidance folks.

[Two Fangs]

When the blower motor is actually moving air, it is slightly side loaded.  I believe that the commutator segments are hitting the brushes making this noise, and not allowing the motor to work at peak efficiency most likely caused by a slightly worn bushing, but heat could also be a contributor.

[TheCMSH]

The bigger brain has chimed in  

[MidNiteFury01]

thanks for the assistance. Good information.