a/c not working...

[Steve-0]

ok here's the scoop my a/c when i turn it on it won't light up and not working, not only that at the same time the control for defrost, vent, etc isn't switching, it's sits on the floor and that's the only place it blows. i checked fuses pulled the control out and checked connections on back everything looks fine any ideas? oh and it's in a 98 silverado.

thanks

[hatzie55]

I had the same problem with my 2000 GMC in late 2004.
I replaced the control module to fix the problem for over a year. One of the transistors stopped switching. I have since had intermittent problems again with the mode door not moving up from the floor when I ask it to.... It seems worse when the cabin temp is high.

[Steve-0]

i noticed last nite with mine is that when i turn the fan off, i can now move it from the floor to vent and defrost and it changes but as soon as the fan is turned on it moves back to the floor automatically. and another thing too is, that when my a/c button is turned on with the fan running it doesn't light up and doesn't kick in, as soon as the fan speed is turned off the light goes on still didn't really check if it's kicking in. What a pain in the a**

[JohnC]

When things interact like that it's usually a high resistance connection, often a ground.