What would cause a 99 s70 blower fan to speed up during braking? Letting off the brake pedal, and the fan slows. This happens in either AUTO fan mode, or manual fan mode. Also, I am using the AC, not the heater, I'm in Texas after all. Anybody else ever had or heard of this problem?

 

Mine did the exact same thing. The blower is on it's way out. I got one from a junk yard for $15.00 and problem was solved. Removal/installation simple. Remove glove box and knee bolster and there it is. (I found detailed instructions somewhere on the web but don't remember where)

When it plugged in the replacement it worked fine. Put the old one back, and when I moved it back and forth the speed changed. When you replace it you will be happy to notice more blower power.

If you prefer not to use a junkyard blower you could buy a new one.

Good luck

 

Also, have you replaced your cabin filter lately?

 

Of note, today when I put the fan control on my car at 100% and vent control for the AC vents, and the air volume from the fan is well below its capacity when new. (It is funny, but as a car ages, we seem to get use to the lower performance of its various parts.)

Yes, I replaced the cabin filter. The old one was very dirty, and now I am wondering if I damaged the fan from overheating. I am going to replace the fan over the holidays and see if all is solved as was suggested. The fan is ten years old anyway.

Thanks for the suggestions/advice.