I have a 2003 trailblazer LS ext with rear heat and air. The rear blower fan is not working correctly. If I turn the **** to high (3) it will run for a second or two then shut off while some times it will run till I turn it off or turn to a lower setting then it will only run for a short time then shut down. Front works fine. any ideas would be great.

 

sounds like switch to me.

 

Is there a way to check the switch because it has two one in the front for the driver and on in the back for passengers. The front is the master control for the rear. It has setting 3,2,1,0,R. the R position is to allow the rear passengers to control the fan speed and temp setting. Same thing happens using the front switch or the rear switch. I took the rear blower out to see if i could find some way online to test it but no luck. I can't even find a new one.

 

You post that sometimes it runs till you turn it off, what position are both main, and back seat switch in when it runs as it should? You also should try to jumper out the front switch, if the rear switch controls it as it should, it's the front, and vise versa with the rear switch. Unfortunatly if it is a switch, more than likely will be the front as it is used more than the rear.

 

The highest setting is where it works as it is supposed to. It will work on other setting just not for very long. Also another thing if i turn the ignition on with the engine off the rear blower works fine for the most part.

 

I was thinking I was acting like it had a thermal protection on the blower motor that when it gets hot it trips till it cools off. but that's just my thinking. I'll go see if I can bypass the front switch

 

Should the blower motor spin freely or will it have a little resistance to it.