Cruise Control Blues

[PUMPERDUDE]

When traveling on not so new roads, my cruise control will disengage when hitting bumps. I think the problem is the brake pedal bouncing and giving a idication of braking and killing the cruise. Anybody else had this problem and found a solution to it?

 

[gitchesum]

My 94 did the same thing. It turned out to be the brake light switch. Replaced it and went on about my merry way.

 

[Alaskaskiff]

Mine did it when the throttle cable started wearing. Looked under the hood and found a big birdsnest of wire. Changed it out with the new style and cruise stopped doing that.

 

[Joe G.]

I had a cruise control problem and it was the brake light switch. I fixed it by readjusting it. This is a simple task but it is not obvious how to do it. If you don't have the service manual you would not be able to figure it out. It is an automatic adjustment. To do it remove the wire connector. Then while the pedal is pressed away from the switch turn it about 30 degrees counter clockwise and remove it. Pull the plunger out a few clicks. It's pretty stiff. Then replace it with the pedal depressed by aligning the tab with the slot and turning it clockwise about thirty degress. Now slowly let the pedal press against it. That will depress the plunger the right amount to adjust it. That may fix the problem. You may want to check the vacuum tube to the cruise control under the driver's side battery box for holes.

 

[MxerChris]

i have been having a problem with my cc also, it just quit working all together, I checked all fuses and vacuum lines and have not found anything out, if the brake light switch seems to be working the brake lights ok could it still be out of adjustment and cause the cc not to work or are there other things I could check?

 

[Joe G.]

racingfanscjww,



Need to know what you're driving. Update your signature for these sort of questions. I know about '95s, but if you are driving one of the late model heaps of computers I have no idea.

 

[MxerChris]

sorry mine is a 95 3500 CC 2wd auto.

 

[Joe G.]

The following is from page 5 - 19 of my '95 service manual. It's about testing the brake light switch after you remove it from the vehicle.



There is a drawing of the switch. There are six pins numbered from the end opposite the push plunger.



--------------------------------------------------

Switch Circuit Identification.



Switch terminals 1 and 2 are for the brake sensor circuit



Switch terminals 5 and 6 are for the brakelight circuit



Switch terminals 3 and 4 are for the speed control circuit





Switch Continuity Test Procedure



(1) Check continuity between terminal pins 5 and 6 as follows:

(a) Pull plunger all the way out to fully extended position.



(b) Attach test leads to pins 5 and 6 and note ohmmeter reading.



(c) If continuity exists, proceed to next test. Replace switch if meter indicates lack of continuity (shorted or open).



(2) Check continuity between terminal pins 1 and 2 and pins 3 and 4 as follows:



(a) Push switch plunger inward to fully retracted position.



(b) Attach test leads to pins 1 and 2 and note ohmmeter reading.



(c) If continuity exists, switch is OK. Replace if meter indicates lack on continuity (switch is shorted/open).



-------------------------------------------------



I assumed that you should repeat test (2) for pins 3 and 4. (I don't think any of the people who write this stuff were English majors. ) Anyway mine passed this test and I adjusted it as I outlined in my previous post. This whole thing is pretty easy because the switch is easy to remove once you know the trick. The thing to note here is that the brake light circuit is NOT used for the cruise control so the switch could be bad on pins 3 and 4 while pins 5 and 6 work fine.



If you have the '95 service manual there is a diagnostic procedure for the "vehicle speed control system" starting on page 8H - 1. If you don't have the manual what are you waiting for? One hour of shop time you don't have to pay for would pay for the manual.

 

[tmarti96]

tachometer flucuation

Joe George,



Perhaps you can help me. I have a 95 3500( see signature) My tach starting acting up, shortly after a TC & VB install. It flucuates rapidly and then sometimes it will quit completely. When this happens, the alternator and A/C compressor quit also. Then the TC begins to shift in and out. When you accelerate in the locked up mode, it will then shift out of lockup in about 2 seconds. I have installed new crankshaft sensor, adjusted to about the thickness of a business card and worked fine for about 30 miles. Then started all over again. Could this be a TPS problem? I am scheduled for throttle cable recall tomorrow AM. Got any suggestions I could throw at the dealer? I am at my wits end of this. thanks.

 

[Joe G.]

WOW! The first thing that comes to mind with so many electrical gadgets going wrong is a bad ground. I would check all engine to chassis/body grounds for broken wires or corrosion.

 

[Missouri Mule]

tmarti96,

Engine speed sensor(crank speed sensor) would seem to be the culprit.

But could be something else.

The fluctuating of tach, alternator quiting, tc messin up some what points to it.

But a/c and no trouble with the trans shifting doesn't.



The engine speed sensor (mainly its connector,loose,burnt, dirty pins are usually the problem not the sensor) indirectly help run a few things on the truck.

Tach, vehicle speed control(cruise), asd relay(generator field), torque convertor electrical engagement, along with vehilcel speed sensor(VSS) and throttle position sensor(TPS) determines when to shift auto trans in and out of overdrive and their mite be a few others.



Check your connection for engine speed sensor.



Check grounds. I'm not sure but several of the items you are having trouble with mite have same ground location.



Check gound to PCM if I recall correctly the ground(for sensors) is located by injector pump on head or intake manifold in front of intake heater.

While you looking at grounds check all corresponding wires(loose broken,shorted) /connections(loose, loose,dirty,broken,burnt pins).

You mite be able to get a fault code out of your PCM.