fan speed switch

have 99 silverado. recently lost speed 5 in fan switch. now have only speed 3 & 4. air and heat work fine as do the flow directers.
looked at control box, switch 'seems' okay.
any help?

Probably the resistor pack. AC Delco 15-8770.

//2000CAYukon

Personally, I would think it is the contact on position 5 in the HVAC controls either burned or broken off

I agree with the resistor theory. At speed 5, the most current is flowed to the fan through the resistor. GM's have high current blower motors, so it is not uncommon to have one go out. You should be able to test with a meter at the fan if current drops out at the high speed, but current is at the high speed switch, that means you lose current at the resistor. Vwala!! Change it out

Mine went out on me 2 years ago. Only had high (5) though , no lower speeds. The blower motor was seizing and blew the resistors. At that time the blower motor assembly was a dealer only item and was almost $200 , plus i think about $40 for the resistors.

2000CAYukon is right, it's the blower motor resistor. I had the same problem in mine, I lost 1, 2 and 3, only had 4 and 5. I talked to a couple GM people and they said it's common for them to burn up.

WATCH though when you go to order your part!!! Chevy changed the design of the part but never changed the part number. There are two different style parts listed as 15-8770!!
AC Delco carries the right one, Advance Auto and Auto Zone don't have the right ones, even tho they say they are for your year vehicle.

I ended up buying mine off www.rockauto.com and paying $5-$10 less then everyone else wanted. GM Parts Direct doesn't stock it anymore. Search the part number and get the AC Delco one, not the Standard one listed. The price for it is $14.65. I put a picture of the standard one below, that's the new model and it won't fit your truck!

They are fairly simple to get to, hardest part is removing the large cover that covers the blower motor itself, it goes from passenger door to almost the gas pedal, I think it was 3 or 4 screws. Once that is off remove the cover for the fan motor, it's right there, you take out two screws and pull down on it (mine sealed itself with the foam a little bit). There is a plug that goes into it from teh back of the fan motor, push on the little clip to release it.

YOU DON'T WANT THIS ONE!!
http://www.smpcorp.com/web_app/catalog/images/RU61.jpg

thanks everybody, sure beats hearing the dealer say, 'i don't know, you'll have to bring it in'.

Just wanted to say thanks again. I found the switch at a local AC Delco dealer ($16 and change no shipping), looked a bit different at the business end (made in Slovenia) but it mounted and works!
fire24resque , right on about the four screws. Only put 3 back for now, the one under the hump is a real bear but I'll get it.