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vanagonman, VW Mechanic
Category: VW
Satisfied Customers: 274
Experience:  11 years experience running VW shop and parts store focusing on VW vans.
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1997 VW Jetta Jazz: doesnt work..the cruise control curcuit is wired

Customer Question

I own a 1997 VW Jetta Jazz. My cruise control doesnt work. I dont know how the cruise control curcuit is wired. Therefore I dont know were to start testing. Please help me....
Submitted: 8 years ago.
Category: VW
Expert:  vanagonman replied 8 years ago.
Do you have a manual or automatic transmission?
Customer: replied 8 years ago.


Expert:  vanagonman replied 8 years ago.
First check for your fuses. You would feel pretty foolish to go to all of the trouble to troubleshoot the system only to have something minor like a blown fuse be the root cause. It should be fuse number 14 a 10 amp.
Now on to troubleshooting:
There are two vacuum valves in the system one on the top of the brake pedal and the other at the top of the clutch pedal. If you look up under the dash where the pedals go under it you should see them. They are black plastic. These switches are both electrical and vacuum. When you push the brake or the clutch pedal it will release the vacuum that is moving your car throttle when you are driving with the cruise control on. Many times the problem with the cruise control not working is simply that one or both of these two switches are out of adjustment and are not holding vacuum. You can easily test this with a vacuum tester. Unhook the vacuum hose going to each switch and with nothing pressing on either pedal they should hold vacuum. If they don't then try adjusting them. This is just a matter of screwing the body of the switch closer to the tab that pushes against the end of it. If you adjust it and it still leaks then you will need a new switch. However many times vacuum leak is the whole problem. If the switches are good look under the hood. You will see a vacuum actuator that has linkage attached to the throttle body. It looks like a black rubber diaphram that is about 2 1/2 inches in diameter with a black vacuum hose coming out of the back. Test this with your vacuum tester to see if it is holding. It should move your throttle while you apply vacuum and hold it.
Trace this line back to the vacuum pump. This is the unit that pulls the vacuum on the system in the first place. There are two lines going to it. Attach one to your vacuum tester and plug up the other one with the end of your finger. The system should hold a vacuum when you pump it and it should hold steady. If not then you still have a vacuum leak somewhere in the system and you can go hose by hose until you find it. There are only a few hoses in the system so it is not a big deal.
If it is not vacuum it is electrical. Contact me again and I can give you the troubleshooting guide for that as well. Most of the time it is vacuum.