Bryanh24

Hey everyone,

So the cruise control on my '91 Z does not engage no matter what. I have tried clicking the set button multiple times while driving, sliding the switch on and off repeatedly, pushing both of my feet up on the clutch and brake pedal to see if it will engage and it does not. These are the things I have diagnosed so far:
- Tested vacuum supply line. Holds 15 inches of pressure at idle.
- Put a volt meter to connections B&D on the servo connector. I get 5 volts at pin D and 0 volts at pin B. This is with the car in accessory mode.
- Hooked up my vacuum hand pump to the vacuum release line and put some vacuum pressure in it. When I press the brake pedal the pressure releases, when I push the clutch in the pressure does NOT release. The car was also in accessory mode for this.
- I followed the FSM for the pressure release switch on the clutch pedal. I took it out, removed the retainer clip, put the clip back in, inserted the clutch pressure release switch into the clip again and it still does not release pressure when I push the clutch in.
- Pushed in on the servo diaphragm and everything works as it should. Throttles open and close perfectly with no sticking. The car also revs when I push in on the diaphragm.

I believe that is all I have tested so far. Let me know if you have an idea of where I should go next. Thanks.

rush0142

You are probably better off replacing the brake light switch. . The cruise control runs through the brake switch. When I bought my 91 Z, the cruise didn't work.....I changed the brake light switch and the cruise control worked. I would start there, especially if its original to the car. $20 part most places


https://www.zip-corvette.com/89-92-b...ht-switch.html