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'90 Climate control & horn intermittent -- Please help.

90SixSpd

Member
Joined
Sep 28, 2014
Messages
10
Location
Gilbert, AZ
Corvette
90 Conv HT
1990 Convert w/ Factory Hard Top, Built 6/1/1990 (Day 152), C68 A/C, 18,614 Original Miles
Intermittent climate control and horn. No codes or warning lights. About 75% of the time when starting the car, the climate control screen goes blank, the blower runs at a high speed blowing ambient air, and pushing the climate control buttons has no effect. If the car is turned off and restarted after an 8 second wait, the climate control screen’s characters populate and the push buttons control the HVAC as designed (can freeze you out on a 116 degree day). Sometimes it is necessary to perform the restart/reset procedure twice. The horn is generally inop on start-up and sometimes the HVAC restart/reset enables horn functionality; more often it does not. Additionally, the A/C compressor clutch is continuously engaged when the climate control activates refrigeration; the compressor does not cycle nor do the radiator fans. Also, when you turn the car off and leave the key in the ignition, the warning chime only sounds once, rather than continuously. I took the car to the dealer and the tech and shop foreman could not find a climate control problem and were unconcerned that the A/C compressor and fans did not cycle (cold start-up, 85 degree ambient temp, climate control set to 80 degrees). A previously owned C4 had the A/C compressor and fans frequently cycling when in the refrigeration mode.
Questions:
(1) With the restart/reset, within what electrical component is the reset occurring?
(2) Is there a single common point/component that could be defective and affecting all items?
Thank you.
 
Have you checked for DTC H History codes? Some H codes will not light up SES light. Know the paper clip trick for codes?

Do you have FSM Factory Shop Manual? I have '90 FSM to check, but check for H codes first...

Welcome onto the boards there.
 
Thank you for replying. Regretfully, I have virtually no Corvette product knowledge and do not have a factory service manual, nor am I familiar with either DTC H History codes or the paperclip trick for codes. The dealer said there were no codes and I pretty much have to go with that, though I don't have much confidence in them.
 
FSM is a NECESSITY. Get RED 2 book set off of eBay, and learn to navigate it. Even if you can't FIX the problem, you can understand the problem, and know when the dealer (or ANY wrench), is taking a fi$hing expedition with your wallet, doing 'new part' Plug N PRay diagnostics

I can check my '90 FSM later today here for a start...
 
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