Cruise control oddities

[Power Wagon]

Randomly, my cruise will do strange things. Once in a while, it just loses 1-4 mph, once in a while it'll gain 3 or 4, and every now and then it just seems to shut off. I've even had it appear to engage on it's own and accelerate.



And then again, it'll sometimes go a long time without any symptoms at all.



I can't seem to pin this down to any one thing, condition, event... It just seems to be totally at random.



If you've experienced anything like this and found the cure... I'd sure like to know.

 

[Old Smoky]

My cruse control works great, most of the time. Twice it has completely quit working. Not long after I bought it, the cruise wouldn't work at all, I couldn’t set it. A couple of days latter I tried it again and it worked fine. Last week I tried to set it but it didn't work. The next day it worked fine. Besides this, it has worked flawlessly.



Mike

 

[Dfeland]

When my TPS went out when I had cruise on it would lose about 5mph when I went up a hill rather than keep up with the set speed. As soon as I fixed the tps it worked perfectly agian. The only other input is speed sensor.

 

[paccool]

Mark, I have had the same type of problems with my 93. Turned out to be the stop light switch out of adjustment. The cruise uses this to turn the cruise off when you tap the brake. For some reason, the switch caused mine to do some of the things you are talking about.



The switch simply pushes into a socket. I thought the switch was going bad so I replaced it. A few days later, same problem. Reached under the dash, pushed the switch back in, worked fine. Figured out that I was bumping the brake pedal when I was getting out and that was pushing the switch out of the bracket. Took a cable tie and secured the switch in place - no more problems. Hope yours turns out to be something this simple.

 

[nascar mark]

Hi Power Wagon.



Looked up vehicle speed control system in my manual and it said 2 possible causes.



Faulty electrical circuit which is a lengthy procedure to diagnose, so test for Defective servo first and if it checks out ok e-mail me and i will type out the procedure for you.



Servo test is easy with a vacuum gauge as it should be at least 10" mercury at idle. If lower check for leaks.



mark

 

[nascar mark]

Stop light switch won't cause engagement of cruise control, only disengagement so i think you can rule that one out.

 

[dslcummins]

Mark



My 92 was shutting off and reengaging, doing crazy stuff. It ended up being the switches in the steering wheel. You can take them out and test them if you have a manual. The switches come in a set, I put the new set in and it solved the problem.



Rodney

 

[paccool]

No, you can't rule out the stop light switch. That was the problem with mine! Seemed the switch was on the edge of turning off but went back and forth. Would increase speed 4 or 5 mile an hour then shut of and come back on. Sure as hell worth looking at before ruling out.

Stan

 

[nascar mark]

Won't hurt to check then. Sorry paccool. Didn't think the stop switch could re- engage the cruise.



mark

 

[paccool]

Mark, I didn't think it could either. It drove me crazy trying to find the problem. Happened to notice the brake lights were on after I got out of the truck once and that prompted me to check the switch for that problem. When I pushed the switch back in, the cruise started working right. I'm like you, thought it would break the circut and turn off. Since the switch was tied in place, there have been no more probs. This may or may not be the problem with Power Wagons but he asked for help and I was just passing along my personal experience.



How does the vacume work in the cruise/ Is that what modulates the fuel?



Stan

 

[Philip]

I have been lurking around here for a while. So here is my $. 02 worth.



When you assembled your CC. Did you check the bulkhead connector for loose terminals? Mostly on the outside of the firewall. These terminals are held in by two very small tabs on the sides of the male pin. With the smooth ride our trucks have. The tabs can crush down and loosen up. Then you get interment problems like the ones you are having now.



Pre 80 models were bad about burning out the main fuse block power feed wire at this point.



Over the years. I have seen a lot of problems with this area.



Did you install the vacuum cut off switch into the CC circuit? On my 93 it has it located behind the driver side hood hinge. This is used to drop the CC if you loose vacuum to the brake booster. Check the vacuum line to it. Also check the T in the line where it splits just before the booster. It is made of plastic and is prone to breaking with age.

 

[Power Wagon]

After reading this through a few times and driving the truck a few more times, I'm thinking it's my switches... specifically, the set/decel and resume/accel switch pod.



I've noticed that even when it's working, finger pressure on that switch will activate it, even though you can't feel it move. I just put my thumb on it and it responds, even though I didn't press. Other times, I have to rock it several times to get it to do anything.





Thanks much for all the info.



Now I gotta see what the stealer wants for replacement parts (GASP!)

 

[nascar mark]

:--) Don't do it Power Wagon, You will have to sell the house,wife and kids. LOL Have you tried spraying the crap out of it to clean connection? Just a idea.



mark