Trying to figure out what I can do to fix this new noise from my HVAC system - it typically starts out pretty intermittent and quiet but after driving for a while it becomes this jet engine noise. Changing temp or recirc on/off doesn't seem to make any difference, but at speeds of "2" or above it sounds like something is about to take off!

It mostly sounds like the noise is coming through the center vent.

Does anyone know what's making this racket?

 

One or both of the main fan blowers. The bearings fail in the fan motors, making this noise.
Cheers,
Tore

 

Thanks Tore - I have a spare HVAC suitcase so I guess I'll try to pull the fans from that and swap them in!

 

Okay, one seemingly good fan pulled from my spare... now the question is can I swap it without pulling the fuel tank...

 

Yes, both are doable w/o pulling the tank. However the fan control module bolted to the backside of the wall separating the frunk from the rest of the car needs to come out--as well as the fuse box must be rested on a towel on the fender. There is a large piece that separates the frunk just behind the fuel tank. That whole piece needs to come out. There is some wiring that will need to come unplugged. No big deal really. The expansion reservoir on the top of the fuel tank DOES need to be removed.

 

+1 - It can be done but its fiddly.

 

I am in the middle of a HVAC removal project right now. I am not replacing the squeaky fan but am oiling the sinter bearings which go dry and make noise. Did this on my last 964 and worked like a charm.
I moved the fuse box, removed the firewall, removed the fuel cell strap to push the tank forward a bit and was then able to remove both fans.

I found this post most helpful on the removal procedure: https://rennlist.com/forums/964-foru...an-ectomy.html
Z

 

Thanks - this is helpful info!

Are you oiling the splined shaft where the plastic fan is pressed on to the motor as well as the bearing itself?

 

I started to but then realized there's no bearing there, duh!

I oiled the bearings on the rear side of the motor, washers lie on top, and a second set of bearings located just below the squirrel cage fan where the shaft enters the motor.
In my experience, the bottom bearings are more thirsty than the top ones.

 

I added a couple of pics here to help others locate the bearings. Drip oil where the tip of the Q-Tip is.

On the rear set, gently pry off the washers then oil and replace washers.



To access the front bearings I put a red spray straw in a syringe filled with the synthetic motor oil I used to lubricate the bearings.

 

Do you have any play in your bearings? My replacements have a little in-out play if I pull on the shaft (maybe 1mm or less) but no side to side play. How do yours feel?

 

Put my fans in yesterday and went on a long drive this morning and no squeaks!

I think that's normal play. Look at the fan blades and see if they show signs of rubbing on the fan housing. If no my guess is that you're good.

I check them by CAREFULLY holding the fan in a vice orienting the squirrel cage vertically (like it is mounted in the car) and then powering the fan up by touching the two terminals you unplugged from the car with 12V power (one wire from neg. term. of battery to one fan terminal and another wire from the positive terminal...) and watch the fan spin. If there is no wobble there then again I say you're good.