The fan motor on my brother'* 2003 GP GT will only operate on the high setting.

I had a similar problem in an old Cavalier. Ended up being the resistor board in the fan housing. But, I didn't learn that until after I wasted the money on a new switch.

Is there anyway to determine which component is faulty? Not sure what the testing procedure would be.

it'* the Blower motor resistor. My brother'* 98 GP GT had the same issue and that'* what it was.

Awesome!

How hard is it to change it on that car? And where did you locate a new one?

umm... the dealer will quote you a bunch cause I think it calls for 3-4 hours of labor alone.

Not sure how hard it is to get to to do it yourself. I don't think it took more than an hour for our mechanic to do it.

I believe my mechanic got the one for my brother'* car from either Napa or Carquest. GMPartsdirect seems to list it for under $20. Might want to call the pontiac dealer and get the proper part number and put it in just to verify it is the right one.

Screw the dealer. Go to Auto Value and pay them $30'ish dollars (was $28.xx the last time I bought one), and then recline the passenger front seat.
I'll warn you it'* not fun if you are over 3 feet tall, but it can be done, and only takes me 10-15 minutes to replace.
There are 2 plugs IIRC, and 3 or 4 screws -the one on the side closest to the firewall is an absolute B!TCH, but I usually just break the old resistor out once I have only that screw left. Then I remove that screw and leave it out when I put the new resistor in -I leave it out because it'* not required and I know me or the next person that changes it is going to curse because I know the resistor is going to burn out -it'* a fact considering every W-body anybody I know has has had this problem.
Just cross your fingers the one in the Regal doesn't go bad -that'* $350+ from a dealer and the only place I've been able to find a Buick Regal Blower Fan module (Digi Climate Control Regals and Century'* used a module, not a resistor) except for Ed Morad, who I just bought one from for $25.75 shipped. He said he has a handful of them pretty much all the time, so that'* a relief if waiting a couple days for shipping isn't a problem.

The one on GMPartsDirect was listed as $13.xx. I just mentioned the dealer to make sure it'* the right pn.

Yeah, I realize the GMPD price is lower initially, but how about after shipping? :? I'm guessing it'* gonna be close, but the local parts store should have one 'RIGHT NOW' -I know Napa, Carquest, Orielly'*, and Auto Value all have them in stock locally, which is very nice to know.
As for going to the dealer for one, I believe seeing how many of the originals have gone bad and the fact that a couple (never seen one go bad either) of the aftermarket units I've installed from Auto Value are still in good working order 3-4 years later it might be worth trying, but then again the originals last about 5-7 yrs, so the AV unit'* may be on their last year or two.

Sweet! Thank you for all the info guys. This sounds VERY similar to what I had to go through on my old 97 Cavy. Couple scraped knuckles and 45 minutes of my time and I was done.

I found a couple good pages on how to do this:

http://www.oqcgp.com/forum/kb.php?mode=article&k=70
http://wiki.answers.com/Q/How_do_you...motor_resistor

I'll do it for him as soon as he buys the part.

Got it swapped this evening. $21 for a new one from Advance Auto w/ a one year warranty.

Took about 30 minutes and got some beat up knuckles!

He'* good to go now! Another satisfied customer!

Good deal. Glad we can help. Onto the Wipers. I'll check the 98 GP service manuals if I can find them.