1994 Z28. Blower motor seems to barely blow air in all the settings but high and doesn't blow any air in high. When it was working the high setting didn't blow very hard anyway. I took the blower motor out and jumped it to 12V and it ran like a charm. I've read a lot of posts that talk about the resistor and/or the relay. What is the test procedure to determine which, if any, are the problem. It's easy enough to jam a new relay in there, they're only $20 or so. But that resistor is expensive! Not something you want to replace just to see if that's it. And could it be the switch itself? Any help is appreciated. Thanks.

 

Are you sure the vacuum operated flapper doors for the HVAC are operating?

Check it per this diagram:

http://shbox.com/1/hvac_vacuum.jpg

 

The resistor is not used for the high speed operation; only the relay is used for high. The resistor (and relay) are used for all the lower speeds. I would replace the relay first, since it is used for all speeds.