The air conditioner/Heater fan setting #4 quit working yesterday in my 1998 Blazer. The other 3 settings still work.

What does this mean? Can I expect the other 3 to quit soon?

Generally does this mean the switch is bad? Fuse? or does the fan motor need replaced?

What are the costs? How hard is it to change? I have replaced the radio before so I know how to take the dash apart.

Any information will help.

 

Probably the switch

 

High speed is a direct 12v feed to the fan motor through the blower motor relay. Swapping the relay with another on like it is a quick and easy diagnostic test. If that doesn't cure it, then you will need to test the voltages at the relay to see if the switch is working properly.

I seem to remember the relay being located behind the glove box.

 

When you say relay, are you talking about the resister that is inside the firewall under the hood?

 

No. High speed is a direct 12v feed through a relay behind the glove box. This bypasses the resistor in case the resistor fails, you would still have high speed fan to defrost the windshield for safety.

 

Stupid question, how do you get behind the glove box? I see there is a latch holding it but I do not want to break it.

 

Mike - this happened to me on my 2000 blazer. The relay is located in the engine compartment on the firewall. About $25 at Advanced Auto... 2 minute fix.

 

Thanks

 

I changed the relay today and now everything works. Thanks for all the help.

 

sounds like the resister is bad