My 99 Expy a/c heater fan blower switch only works in the two highest settings. I figured it was the rotary switch on the dash so...

I bought and installed a new switch, but it still does the same thing. The first and second positions do not turn on the fan, but the third and fourth work like they should.

What's down the line from the switch that could cause this? I'm tired of doing the freeze-roast thing where I switch it off then turn it on high when it gets too hot in the car.

BTW. The rear air system works fine, its just the front (dashboard) vents that are affected.

Any help would be much appreciated!

 

Do a search on here for HVAC or something similar, I had the same problem and my mechanic fixed it. It was some kind of relay that is under the passenger side of the dash.

 

Thanks!!!

I did find it using a search under HVAC. I tried doing a search using other key words before posting but didn't find it then.

Here's a cut/paste I found. Hopefully this will help the next guy who does a keyword search using "fan control switch".

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I had this exact problem a few weeks ago. The first two speeds on my HVAC system were not working. I replaced the switch, but that did not resolve the problem. Eventually, I removed and examined the switch resistor, found under the passenger side of the dashboard to the left of the fan motor (about 1 x 2 inches, brown, has wiring harness - 4 wires I think, and held in place by two bolts). The resistor showed significant corrosion damage. Once replaced ($15?), the HVAC blower worked perfectly.

BTW, if your 1999 has rear air, the resistor for the rear fan motor is identical to the front. It can be easily viewed and accessed by pulling off the access panel located on the driver's side of the cargo area.
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I'll be checking this out in the morning and hopefully can get a part on Saturday. If not I can get things loosened up and fix it Monday at lunch.

As always this site has an answer.