I took the 90 Corvette for a ride yesterday. The buttons that control the air distribution did not want to respond but I got the circulation button to turn on the system. When I got to my destination, the buttons would not respond to any settings including off. I shut off the motor and did what I went out to do. On restart, The fan motor/temp control system kicked on and is apparently stuck in one setting. None of the lights over the buttons work, fan speed control etc. The radio will not work, the clock is stuck on 1:00 and none of those buttons work either. So in a nutshell, there is power to the unit, the digital readout screen where the outside temp displays reads a short dash and two long dashes and none of the selection buttons respond. I disconected the battery to see if it would reset. No luck there. I'm going to the FSM to see what I can dig up but any voice of experience is welcome.

sounds like a fuse failure... that's where I would start.

Well call me dumb as stone. I must have somehow triggered the diagnostic mode in the unit thus the code. I dont know why nothing worked but apparently it does that in diagnostics. Yesterday when I got home I sprayed the buttons with electrical contact cleaner because they were acting up before this. I went to the FSM and it said to hold the up and down temp control button down for 5 seconds to see the diagnostics. I must have done that while I was fiddling about yesterday. I went out this morning to go see if that's what I had done and everything was working fine. Even all the buttons engage thanks to the contact cleaner. So I guess it's just me learning something new everyday. Even after 6 years of ownership. Thanks for the response Andy. That's the first place I went when I was trying to figure it out. All my fuses were good. I checked all the ones in the fuse panel.

It apparently just resets as it sits overnight. When I drive around all of a sudden all the buttons become inoperative. The A/C cooling system goes into a default setting and stays on. The radio locks on whatever station it was on and the volume control. The outside temp display then displays - -- -- or -- - -. One of the two. None of the control buttons will work at this point. One time the radio kept playing even with the switch off. Previous to this episode, the antenna stopped working so I just left it in the up position. So, what do you think? Short? Relay? Antenna related? Just another one of those whacky things? It doesn't effect performance but I sure would like to be able to control my radio and temperature options.

I've had episodes where the HVAC controls would become inoperative, but I think maybe the contacts need cleaning.
My antenna went out last year too, but I haven't seen any of the other symptoms you've described. Maybe it's a relay/short, as you suggested...I'll look around later and see if I can find something about this anywhere..

Sounds like:

Gremlins



Actually Tommy I looked a little and it seems like this is a common problem. There was a TSB on it back then but I can't get the info. I know some guys have alldata accounts and maybe they can access it. TSB 903781A

First thing recommended is completely taking the control unit out, taking it apart, and cleaning all the contacts. If that doesn't work you may need a tech 1 to scan it and see if there is a problem with the pcm. Also make sure to check all the wiring connections (including the blue wire which apparently controls the radio and the hvac).

Good luck,

Matthew