94 940 Cruise Control Problem

I have a 94 940 Turbo and it has developed a problem with the cruise
control. It works fine for about an hour then cuts off. It can be
reengaged but cuts of increasingly frequently until it will not reengage
at all.

I've had it checked and there is no vacuum leak and the shop could find
nothing wrong, since it worked for them.

Any one have any ideas?

 

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.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

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?

Dave

 

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.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

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.


--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

similar prob

Mike
I enjoy your posts = very informative. My 94 940 has an intermittent brake dummy light coming on for some time now. Then the cruise quit. So can you give instructions on how to check the fuse did you say earlier? clean them? or look at the hoses?