Hi guys, I have an 02 blazer xtreme with the fan speed not working on the high (4) setting. 1, 2, and 3 work fine but 4 just shuts off the system. The blower motor was replace a couple of years ago. I just replaced the resistor pack right beside the blower motor because I read somewhere that that could cause the high speed to go out. No fix and out the cash for that part. So any advice on this would be greatly appreciated as I live in Florida and it's hotter than Satan's armpit here right now.

 

There's a relay on the firewall in the engine bay that sits right above the passenger valve cover area just for the high speed control of the blower fan. It's literally called the high speed relay... It's a basic 4/5 pin relay in a fancy housing that uses the standard GM relay plug. I've had to replace mine, I just grabbed one out of a junk yard Blazer. Some models have multiple relays in the same area for different options on various years, best bet is to swing by a local junk yard and load up on 3 or 4. That way even if one of them you grabbed is no good, you have another to try, or just spares for in the future, as they're quite common to go out...

 

I am having the same problem. I have a 96 blazer 4 door 4x4. Replaced the relay, resistor, the relay plug because it was melted in one place and the fan switch. The plug to the motor blower is reading 13.5 on the multimeter. The blower works on speeds 1-3. But it will shut off for a few seconds here and there and then come back on. It is grounded. If anyone has anymore ideas they would be greatly appreciated. It's driving me nuts. It has been really hot here. Also if this helps the blower worked on high and was cutting off and on. The fan switch was smoking really bad if you switched down to 3 or lower. So I just left it on high. Then this summer it quit working completely.

 

On your 02 there is a separate fuse in the under-hood fuse block for the blower high setting (4). If that fuse is blown 1-3 works and 4 is dead.