Komiller118

1996 C4 Coupe. so my cruise will just disengage when driving down the road. after a few minutes/miles I can use the set button and the cruise will engage. after a few miles it will cut off again. same scenario over and over. It works fine for about the first 60 or so miles and then the described scenario starts. All of the functions on the multi switch work like they should otherwise. I know the vacuum hoses are in pretty bad shape, but I cannot find where the larger one on the servo goes.........

aklim

Don't have books here but those are what I found

PatternDayTrader

Check the brake light switch adjustment first.

Something that intermittent really makes proper diagnosis difficult. I would probably replace the on/off switch if you cant find anything else obvious (such as the brake light switch adjustment). Your only other option is to wait until it gets worse unless your going to drive around with a test light in the car and your going to stop on the roadside while its in the failed state.

pcolt94

I can almost guarantee you that it is the 3 part brake switch. This is a classic symptom of the switch contacts being bad and having high resistance. This is the most common problem of cruise and the switch contact is almost always the problem. Many people have fixed their problem with this repair.
(The 3 port check valve should be checked (for cracks) however poor vacuum will usually show up with poor control of the vents and air not coming out in the right places).

I have done some real extensive work on the system and if you wish to read my thread to see where I went for troubleshooting. Took a long time to figure it out but then it seemed so simple and logical where mechanical parts age.

https://www.corvetteforum.com/forums...-for-94-a.html

Komiller118

thanks for the responses. I will check the simplest first, the brake switch and go from there.

jmgtp

Mine did that - it was the switch at the top of the clutch pedal throw. The switch wasn’t faulty, just out of adjustment. They are threaded and it somehow loosened (I think jumped he plastic threads) And sometimes it would be ok and work then just cut off. Like others have said, could also be the similar switch on the brake pedal or the vacuum lines leaking. Suppose it could also be a problem in the stalk, servo, or calling to the throttlebody.

gerardvg

Yes the brake switch is the usual culprit the one with two contacts at top and two end was the culprit , when I pulled mine apart after intermittent meter readings one of the contacts had broken.
Some of these brake switches are hard to get

aklim

You drive a C4, you best be prepared to hear the words "OBSOLETE" or "No Longer Available".

My case was the hose was leaking.