GMC Repair: HVAC display not working, negative battery cable, ac compressor

Question
Hi,
  I have a 1991 GMC 350 2 wheel drive pick up.  Not winter driven.  Started the vehicle to discover HVAC display not working-no blower speeds, no vent control, nothing.  Blank.  Engine stays on high idle, AC compressor kicks in and out.  Fuse is good.  Help!  Thanks Terry.

Answer
Hi
three things for you to try.
1) just unhook the  negative battery cable. let it stay for a few mins. Hook battery back up, see if that fixed it.
if not
2) Unhook BOTH battery terminals. Now touch both terminals together ** BOTH UNHOOKED FROM THE BATTERY** for 30 seconds. This clears "Logic Lockup". After time is up, hook battery back.
if still
you'll need to get a new HVAC Control head (HVAC Controller). You may now be able to purchase these aftermarket, check some of your local parts stores.
I hope this helps
JUST advice from experience.
Good Luck
Paul