UrS4 Frequently Asked Questions

I decided to try to fix my cruise control today. Coming back from Montreal two weeks ago was the first time I really missed having it. I guess my right foot is getting frail.

When diagnosing the problem I should have tried the simplest things first. Instead I started with what I thought were the most likely faults, based on what I’ve read about other people’s cruise problems.

First I removed the knee panel and inspected the clutch and brake switches. They seemed to be properly positioned, and the vacuum and electrical connections were secure.

Next I located the vacuum pump. It’s behind the hydraulic fluid reservoir. I went and searched through a few boxes for my hand vacuum pump (I’m moving soon and most of my stuff is already boxed up.) I disconnected the cruise pump and plugged the vacuum line onto the hand pump. I was able to pull 660 mmHg of vacuum and it held for many minutes. Okay, that’s good, no vacuum leak. (I should have done this before bothering to inspect the pedal switches visually.)

Then I removed the vacuum pump and brought it inside. After more box rummaging I found my bench power supply and my digital vacuum/pressure gauge. When the vent solenoid and the vacuum pump are engaged, the pump will pull 550 mmHg of vacuum. Disconnecting the pump but keeping the vent solenoid (really the don’t-vent solenoid) engaged, the pump held that pressure indefinitely. So the pump and vent work. That’s good.

Next step, pull the connector from the cruise control electronics box behind the glove compartment and check the column switches and wiring. For this I followed the bentley procedure. And lo and behold, I had infinite resistance on the “Set” button (pin 4 to pin and 2.7Mohm on the ON switch (pin 11 to pin 5).

So now I start disassembling the steering colum covers, only to realize that there’s no way to get to the switch connector without pulling the wheel, which I didn’t want to do.

So at this point I decide to find some contact cleaner and spray the crap out of the switches at the end of the stalk. Well, lots of contact cleaner and switch wiggling later, and my cruise control works. If I had done this first I would have had to disassemble nothing at all. Oh well.

Now I’ll have cruise control for the drive to Watkins Glen tomorrow. Yay.