94 940 Cruise Control Problem

Broken solder joints in the control module? J

When the cruise quits, hook your foot under the brake pedal and pull it toward you. Most cruise problems I see involve pedal switches coming out of adjustment.

See if your brake lights stop working at the same time.

My cruise stopped working and it was the bulb out relay.( 94 940 ) Bad solder joint (s) I believe it was pin 54 L R or N.

Apparently the cruise gets a ground through the brake lights.

Thanks I think I knew that.

My brake lights work but I do have an occasional indication of bulb failure, which I thought was a bad ground. Some times the brake light andsometimes the turn signals.

Thanks I'll try that.

I've also determined that the 'resume' function doesn't quite work right either.

Where is the control module?

I also have a 94 940T. Cruise has not worked since I bought the car. I have adjusted the brake switch to the shortest distance. The vacuum hoses have all been checked and/or replaced on a recent engine removal project.

I don't know where to go next. I can't figure out how the thing is operated.

Any help from the forum?

Assuming your 940 is the same as a 740, there's a control unit mounted on left side of the driver (LHD) behind the kick panel. There is an electric vacuum pump controlled by this unit (engine vacuum is not used) that is mounted to the left shock tower, 6-12" from the top. The actuator is on the intake manifold, connected to the throttle pulley by a short cable. The switches on the brake and clutch pedals not only turn the pump off electrically, they dump any vacuum in the system to release the throttle.

If you pull the vacuum hose off the pump and apply vacuum to it, the throttle should start to open. (Note there is a hose that goes from one end of the pump to the other, ignore that one, the one you're interested in is the one that goes toward the actuator and firewall.)

All the problems I've seen with this cruise control has been related to vacuum problems, hard cracked hoses, rotted actuator, or misadjusted switches.

My shop has checked and found no vacuum leaks. They also adjusted the switches. I'm leaning toward the actuator, since the resume function seems broken as well, that could be caused by a weak actuator which doesn't have enough "pull" due to vacuum leakage in the actuator itself. The only other part it could be is the vacuum pump, assuming my shop is right.

It should be easy to check the actuator, it will either work or leak. It can't be weak, it relies on unchangeable laws of physics - if there's a vacuum inside it, the force it exerts is proportional to that vacuum and its surface area. If the actuator pulls smoothly, and there's no leak it's OK.

Also, (as someone else mentioned) I did forget the "lesson of the brake lights" - if you have no brake lights, you have no cruise control. This I've seen more than once - the failure being in the bulb failure sensor, or corrosion at the taillights.