The AC/Heat Blower Motor on my 1999 Tahoe 2wd 130,000 miles works intermittently. When it does work the fan does work on all speeds. If the fan is not working I can hit under the passanger side dash and it will start working. If the blower is on high it tends to stay on. If I turn it to low then it may stop working. The blower stays on better at all speeds when highway driving. Is it the relay, motor or grounding wire. Where would I find each? I called a dealer and all they said was that it could be anywhere from just inside the dash to the back of the dash so they couldn't quote a price. (Anywhere from $120 - $650) Any help would be appreciated.

My best guess would be the switch itself. The relay comes into play when you switch to "high". All other positions go through a resistor for slower fan speeds.
The dash is not connected to the heater plenum, but by giving it the old "butt kick'n" method maybe it's kick'n the switch into submission?? Be my 1st choice!!..............Steve

Thanks for the switch idea. I will check it out. However if I bump the switch or hit the dash by the switch, the blower does not kick on. If I hit the bottom of the dash on the passenger side then the blower kicks on (get it -- ha ha) almost every time.

Well Then: All kick'n aside, "what we have here is a failure to communicate". So for now lets forget about the switch and look at 1.) the fan itself, 2.) the wiring and connectors to the fan & 3.) the high fan relay. Looking at the schematics, all the lower speed power goes from the switch through the resistor and through the "high" relay to the fan in the relay's "relaxed" position. When you turn the switch to "hi" it "energizes" the relay and sends a full 12v to the fan. So, the relay & resistor are located on top of the plenum to the left of the blower motor. You should be able to see the wiring to the blower by the right door jam.

What I said before about the power going only through the relay on "high" was not correct..............Steve

Thanks for the info!!!! Do you think it is the relay, resistor, motor or ground wire based on the detail about how it functions and doesn't function. Which would you replace first?

Check everything else first, but you're going to be replacing the blower motor itself. Trust me, I just put one in my Tahoe. It did the same thing yours did, ran intermintently, shut off on it's own, wouldn't turn on...and a good whack w/ a rubber mallet(aka 'the switch)on the plastic cover over the motor
housing always brought her right back to life. The reason that works is the same reason that a starter that won't turn works when tapped. Bad brushes. --The install is pretty easy. You will have to take out the glove box, and the nuts that mount the blower itself aren't too easy to get to so it takes a lot of patience. Notes - 1)take your time 2) remove the cover slowly so you don't break the tabs that hold it on 3) you also may have to swap the ground tang from the old motor to the new(depending on where you get it, I got mine from the dealer) and if need be, plug in the motor and test it out before re-installing it 4)the instructions(should you choose to follow them)will tell you to cut the end of the hose off to fit it over the barb on the new motor, but you really don't have to - I actually found that it fit perfectly well w/o modification. Front to back it took me less than an hour to R&R mine, and that includes cigarette and beer breaks, all the while BSing w/ a friend. Like I said check everything else first just to make sure. Good luck w/ her. Later. M.

Thanks for the info. Just what I needed. I will try it out.

Installed the new blower last night. Works like a charm. TKS

Just replaced the Blower Motor Resistor (AC part #15-8788) in my 99 Tahoe and that solved my problems. The blower would only work on High but no other setting. Paid $19.40 plus tax from the dealer for it. But a local discount parts store had it for 12.57 plus tax if I wanted to wait a few days for them to get it in. The resistor is located on top of the heater box. Two screws hold it in. Take out the glove box (easy job !!!) and you will see it. Took me maybe 30 mins for the whole job. Do it yourself and save about $200 bills.

bringin an old thread back to life here. this is what I found in our '02 tahoe rear ac...

http://i28.photobucket.com/albums/c249/jon96ctd/work/0823071010.jpg


It's the plug from the resistor to that plugs into the blower motor. It was really nice of GM to not put a plug on the resistor side of that wire and a cheap plug on the motor side...so when it melts you have to buy the whole resistor. can't wait to find out how much $$ they want...