I saw someone posting in the parts for sale section for the cruise control module that mounts under the driver's side storage bin, and that triggered me to ask about possible cruise problems on my 85 GSL-SE.

I was fitting the bins, which I recently bought, into place and noticed the "extra" box in there, sort of near the amp, and wasn't sure what it was. I did notice, however, that there is a black wire hanging loose with a bolt-on type connector which appears to have been crimped at the factory. Looking at it, my first assumption was that it was a ground wire, which I thought was odd since the control box is mounted to the metal of the car which should, in theory, be a pretty good ground.

Now that I know what the box is, I'm holding off on putting the bin in place so I don't have to take it back out when I go to fix the cruise control. The problem with the cruise is that once turned on and "set", the car will accellerate -- as though the cruise was just instructed to "resume" a rather high speed.

I realize that you're probably thinking: "Well, dipstick, hook up the wire to a good ground and see what happens when you turn on the cruise!", but I'm still working on getting the front end back together at the moment (and there's snow, ice, and salt on the roads). So, since I have the bin out of the way *anyway*, any chance that hooking that up to a good ground would fix my problem? It seems like a long shot to me, but then, I have very little understanding of exactly how cruise control is supposed to work!

Thanks much!

 

Okay, here's the quick long-and-short of how the cruise control works in an effort to help you get your SE back to proper functioning;

First off; I wouldn't reconnect that black bullet connector unless you KNOW where it's supposed to go. If you see another connector there that looks like it just came undone, you can give it a shot - but I would be VERY hesitant to hook that up to a ground without knowing what it's for. As an aside - there is another set of plugs under the shift boot that 'appear' that they belong together, but if you hook them up together, you cause major problems with the car.

Back to the cruise control. I would expect that since you describe the car as accelerating as if under a command to 'accelerate' from the column control - I would first look at the wiring in your cruise column before looking elsewhere. It could be as simple as a shorted out 'accelerate' wire that's telling the cruise system to speed up.

This is basically how the system works; when you set the cruise control, it senses the current vacuum setting of the engine intake via the associated tubing that goes to the large, round container next to your passenger side strut mount. This vacuum pressure is held in the system so that when the pressure from the engine drops (as in decelerating while going up a hill), the result is that an internal diaphragm contracts and causes the actuating cable to pull on the throttle, increasing engine speed (and vehicle speed).

Conversely, when going downhill and the car is accelerating beyond your 'set' speed, the internal diaphragm expands and the cruise throttle cable is slackened which eases the throttle setting, slowing the engine and car down.

The cruise speed can be 'adjusted' while underway by use of the column mounted cruise controls - which either bleed vacuum pressure from the diaphragm (coast), allow for greater pressure (accel), or bump up the pressure by a small fixed amount for incremental increases in speed, such as adjusting to a slightly higher cruising speed to keep up with traffic (usually 2mph, or close thereabouts).

In your car, if it immediately tries to accelerate, it could be a vacuum leak going to the solenoids on the passenger firewall, a problem with the air cannister (diaphragm), or the control unit located behind the driver's seat, or wiring, as I originally stated. The system is actually pretty simple, so it may be process of elimination to help you identify where the problem resides.

Post back if you have more questions on this, HTH,