Hey all I am new to the site but have found it very helpful already. Have an 01 blazer and the heater fan works on only the fourth or highest setting and then after a couple of minutes it makes a nasty grinding noise. It sounds like it coming from the glove box or around there. It does produce heat though. Any ideas would help.
Thanks

 

Sounds like the resisters are blown on your fan. The resistors should be located in the heater duct passenger side, you'll have to remove and replace that

 

I agree it sounds like the blower motor resistor. There is a good write up of how to replace one in the DIY section of this forum. Not a very hard job.

 

Awesome thanks a ton for your help and that write up is amazing

 

If the motor is making grinding noises, the bushings are probably worn out. When this happens it causes amperage draw to increase, which is usually what burns out the blower motor resistor.