Ac and cruise control vacuum test
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
Ac and cruise control vacuum test
1989 auto. C68
when i I hook a vacuum tester to the hard plastic tubing going into the dash to the ac unit, I can pull up a vacuum, but it will slowly release. Is this normal?
Should i i be able to hold vacuum on the line going from the vacuum air diverter check valve into the cruise control?
Still trying to trouble shoot cruise control problem. It comes on and tries to hold speed, but kicks on and off constantly to maintain speed. Very uncomfortable
when i I hook a vacuum tester to the hard plastic tubing going into the dash to the ac unit, I can pull up a vacuum, but it will slowly release. Is this normal?
Should i i be able to hold vacuum on the line going from the vacuum air diverter check valve into the cruise control?
Still trying to trouble shoot cruise control problem. It comes on and tries to hold speed, but kicks on and off constantly to maintain speed. Very uncomfortable
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
The info in this link may help...... especially the later posts:
http://www.corvetteactioncenter.com/...t-working.html
http://www.corvetteactioncenter.com/...t-working.html
Thread Starter
Drifting
Joined: Dec 2012
Posts: 1,504
Likes: 73
From: Georgetown TX
After reading your link, I thinking the vacuum dump switch on the brake pedal is bad. My ac works fine and my cc does work but not right. For example, if you set cc at 55 on level road, no hills, it will kick on as soon as speed starts to decease, but not smoothly. It use to work fine.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 207
From: Orlando FL
Did you first check the 3 hose check valve under the plastic cover on top of the right side of the engine for cracks or breakage. If it is leaking it may cause a problem.
Had a similar problem, did a lot of work and big write up. The servo can be checked but you need a power supply, schematic and know theory of operation. But they don’t usually go bad and would not focus in on that at this time.
You question is a common one which speed may drop out or change. The most common part problem is the 3 section switch on the brake pedal. One section is for cruise, second is convertor lock up and third is brake lights. The cruise portion develops high resistance on the contacts and causes all kinds of problems
Once removed this can be measured knowing which contacts to measure. Many people just replace this switch assembly. However it does come apart and I cleaned all the contacts in it 10 of more years ago and all is still perfect.
Check the thread see what you think
https://www.corvetteforum.com/forums...-for-94-a.html
Had a similar problem, did a lot of work and big write up. The servo can be checked but you need a power supply, schematic and know theory of operation. But they don’t usually go bad and would not focus in on that at this time.
You question is a common one which speed may drop out or change. The most common part problem is the 3 section switch on the brake pedal. One section is for cruise, second is convertor lock up and third is brake lights. The cruise portion develops high resistance on the contacts and causes all kinds of problems
Once removed this can be measured knowing which contacts to measure. Many people just replace this switch assembly. However it does come apart and I cleaned all the contacts in it 10 of more years ago and all is still perfect.
Check the thread see what you think
https://www.corvetteforum.com/forums...-for-94-a.html
Last edited by pcolt94; Apr 22, 2017 at 10:32 AM.
