Few problems on a 1990 ZR1

[mike100]

It is a known issue on all C4's with the automatic climate control that the button contacts should be disassembled and cleaned as well as the electrical header on the main plug.

not your issue, but also want to mention that the operation of the early vs late programming on the chip is also different. I can't get a/c on the straight vent button on my 91, but it works all day long when auto is selected. My 95 worked a/c on any vent selection.

[scottfab]

Originally Posted by mike100

It is a known issue on all C4's with the automatic climate control that the button contacts should be disassembled and cleaned as well as the electrical header on the main plug.

not your issue, but also want to mention that the operation of the early vs late programming on the chip is also different. I can't get a/c on the straight vent button on my 91, but it works all day long when auto is selected. My 95 worked a/c on any vent selection.

You'll want to clean them and apply dielectric grease. The problem is with the quality of the gold/tin contacts. The metal is suppose to be pure enough not to rust. It's not. The dielectric grease keeps oxygen away from the metal.