ZV

OK, the only niggling issue with my 944 is that the cruise control doesn't function. Now, I know. Most of you are probably thinking that it's not a big deal, who drives a 944 at a constant speed like that anyway. Well, normall I'd agree but I have to drive the car from Ohio to Seattle at some point and I would really like to have a functioning cruise control when I'm on those freeways out in Montana and the Dakotas.

How does one test the cruise control unit to see if the failure is there or in the switch in the steering column? I un-plugged the molex plug from the cruise control unit and applied dielectric grease to all the terminals hoping that it was merely a bad connection somehwere, but that didn't give me any improvement.

Right now, what happens is that if I push the cruise control lever forward, it will _sometimes_ cause the car to accelerate. However, it never sets the speed and the car never holds a speed. All it will do is accelerate for the duration of the time I'm pushing on the lever.

If it's the switch in the column, how much am I looking at? And if it's the control unit, how much am I looking at? Replacing either seems to be a pretty straightforward job.

Aaron

951Tom

Try re-soldering all the electrical connections in the brain. Then take apart the drive motor under the hood and clean it's internal connections. There are many here that wish they could get their c/c working, me being one of them.

ZV

Anyone know what readings I should get when I jumper the contacts in the molex plug? Seems like I could trace it with my multi-meter that way.

Travis - sflraver

http://www.rennbay.com/tutorials.html

on that link there is a "cruise control troubleshooting" link. Check it out. May give you a place to start.

Spock 951

I had the same exact symptoms on my '87 951. I followed the procedure on the link that Travis gave above to clean the contacts in the servo, but that did not fix the problem. I have the service manual, which has a pretty good troubleshooting guide for the cruise control, and went through all the troubleshooting procedures, and it turned out to be the "brain" being defective. I had my friend (in the electronics repair business) take a look at the unit. He resoldered some of the suspect joints - mainly the ones from the connector to the boards - and it worked perfectly after that.

I had purchased an extra brain at the Hershey swap meet (hoping I would get lucky and get a functioning unit), but it turned out to be bad as well. My friend is currently re-soldering that unit. If it is repairable, I will put it up for sale.

If you need exact troubleshooting procedures (to eliminate the possibilty of having a bad switch somewhere), I can give you all the details. But it sure sounds like a bad brain to me. Disconnect the brain, pull out the board, and take a close look at the solder joints near the connector. Use a magnifying lens, as you may not be able to readily see the bad joints with the naked eye.

Keith

Sasha

The link is probably good. I also agree that Factory Manual has a pretty good troubleshooting guide that includes voltages, currents and control signal waveforms.

I would caution to take very good care of taking the servo unit apart! It is not clear how to put it back together – I spent some figuring out how it went back. My CC is broken as well, but my drive to work is only 3miles, so I don’t worry about it.

As far as cold (broken) solder joints, just re-flow them anyway even if you can’t see cracks. The failure could be internal to the solder or in its contact with the board’s trace. To re-flow the connection, just by a $10 soldering iron at radioshack and some solder. It is pretty easy. Make sure you don’t connect to adjacent traces though!

Hope this helps.