Intermittent cruise control function in 1987???

[mthomas58]

I've got an intermittent functioning cruise control - VERY intermittent actually. It worked on the way to Hilton Head in 1987 and not again until a trip to Winston-Salem on Monday and it did not work on the way home.

System has a brain that I know can be rebuilt or replaced, column switch and engine compartment servo. I can hear a click on the column switch when I try to activate it. Intermittent function leads me to think it is a vacuum problem.

What say you here?

[Jerome Ryals]

Mark, I also have an 87 with a similar problem but mine will work, stop to refuel and leave - - won't work, and it won't work again until you stop shut down, etc. I am also curious on this one.

[rgrimm]

Don't count on it being vacuum. Mine was intermittent, and it turned out to be the brain. Cold solder joints can be intermittent when they start to break.

There is a troubleshooting technique with an electrical meter that rules out switches, etc. I believe there's at least a copy of it in the Bentley manual (which I don't have with me, so I can't give you any specific information).

[Tim Polzin]

Originally Posted by mthomas58

Intermittent function leads me to think it is a vacuum problem.

What say you here?

I thought the 87 and later used the electronic cruise with the servo, not the vacuum system as in the 86 and earlier?

Tim

[Por_sha911]

Swapping out the computer box is a 5 minute job. Trade with someone and you'll find out if its the computer.

[mnmasotto]

I have a 1987 Carrera with the same cruise control problem. Although I had my CC brain rebuilt I continued to have the same intermittent problem. I also replaced the column swith, cable and vacum hose but no fix. My mechanic said the cc systems on these cars are notorious for breaking down. After replacing the majority of the parts my wallet gave up. I figured I spent too much money and will have to live without it.

[RoninLB]

I use a mechanical throttle

works good enough

[janz]

Where or who did the rebuild on your CC brain? I have an 86 and had mine rebuilt by Beckman and solved all my problems. One other item was that if your speedometer is also working intermitent that would cause your CC to do the same as it uses the electronic sensor to operate.

[mthomas58]

Originally Posted by Tim Polzin

I thought the 87 and later used the electronic cruise with the servo, not the vacuum system as in the 86 and earlier?

Tim

There are two vacuum line connections on the top of the servo on my 1987...the one to the rear (nipple due south of #42 on the diagram) comes off the T-connector.

[porschenut]

It's the brain. I had exactly the same problem with my '86, and after swapping the brain with a good one it has worked perfectly and consistently every since.

[ShakinJoe]

I have an entire brain and servo assy that I took out of my '87 track car if you are interested in buying. It does work.

[Tim Polzin]

Originally Posted by mthomas58

There are two vacuum line connections on the top of the servo on my 1987...the one to the rear (nipple due south of #42 on the diagram) comes off the T-connector.

Mark:

Didn't realize the 87 still had the vacuum servo. Wonder what year they went to the later unit?

Tim