Cruise control vacuum dump switch
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Cruise control vacuum dump switch
89 auto. Stock
cruse control was not working. Using a vacuum pump, I found vacuum was not holding in the hose that goes thru dash to dump switch on brake pedal. I disconnected hose from switch, and it held vacuum. I pulled switch and found it would not hold vacuum at all. Order new switch and found new switch pumps up, but starts loosing vacuum right away also. I have ordered new switch. Am I correct in the fact that the switch should pump up and hold vacuum until brake pedal is applied dumping vacuum. It should not leak at all?
cruse control was not working. Using a vacuum pump, I found vacuum was not holding in the hose that goes thru dash to dump switch on brake pedal. I disconnected hose from switch, and it held vacuum. I pulled switch and found it would not hold vacuum at all. Order new switch and found new switch pumps up, but starts loosing vacuum right away also. I have ordered new switch. Am I correct in the fact that the switch should pump up and hold vacuum until brake pedal is applied dumping vacuum. It should not leak at all?
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
I'm referring to the vacuum switch mounted near the brake pedal With cruise set to a certain speed, using the brake pedal will dump vacuum, basically turning off the cruise control until you set it again
Instructor
Joined: Jun 2015
Posts: 128
Likes: 13
leaking switch
89 auto. Stock
cruse control was not working. Using a vacuum pump, I found vacuum was not holding in the hose that goes thru dash to dump switch on brake pedal. I disconnected hose from switch, and it held vacuum. I pulled switch and found it would not hold vacuum at all. Order new switch and found new switch pumps up, but starts loosing vacuum right away also. I have ordered new switch. Am I correct in the fact that the switch should pump up and hold vacuum until brake pedal is applied dumping vacuum. It should not leak at all?
cruse control was not working. Using a vacuum pump, I found vacuum was not holding in the hose that goes thru dash to dump switch on brake pedal. I disconnected hose from switch, and it held vacuum. I pulled switch and found it would not hold vacuum at all. Order new switch and found new switch pumps up, but starts loosing vacuum right away also. I have ordered new switch. Am I correct in the fact that the switch should pump up and hold vacuum until brake pedal is applied dumping vacuum. It should not leak at all?
I just got my cruise working... on mine , the servo has 2 solenoids, and to make the throttle open, you need to supply power to both of them.. servo pins a&E get 12v, ground is pin C. pins B and D is inductive pickup sensor for servo position feedback. Solenoid resistance to ground s/b 20 ohms...
My problem was one of the solenoids was stuck open. When I apply power to each solenoid, they should each click.
You might check those servo solenoids... FSM troubleshooting manual came in pretty handy... altho I didn't follow the steps exactly.
Good luck
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Instructor
Joined: Jun 2015
Posts: 128
Likes: 13
The vacuum dump switch is an emergency system to stop the cruise in the event the electronics fail in a "full throttle" mode. This is why the diameter of the hose is bigger than the vacuum supply hose. You could plug it off as a test to rule out the vacuum dump switch. Of course, this has some danger involved, as defeating a safety system is seldom a good idea. But it would answer your question immediately.
Be careful out there...
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Got new switch today. Pumped it up and vacuum dropped slowly to about 10 and held steady. Tried the other two, one would not even pump up and the other pumped up but would fall down to zero very quickly
Instructor
Joined: Jun 2015
Posts: 128
Likes: 13
