Cruse Control

[KA6QGR]

I have a lot of histoy on this problem 1993 4x4 250. List of problems: Brake will continuosly indicate breaking unless i hook up bungi cord. Cruse controll will accelerate or decelerate with no constancy. At times i can get resonable controll and then it will take off with no warning. I have a new master brake cylinder. I have had this problem for months. I have looked in the data base for help and seen none. I have 290K+. The speedomiter sender seems to be in good conditions. I am hoping i have given enough information. Is there anyone who can advise me?

 

[GerryDrake]

Brakes tripping it ?

I am just shooting from the hip here, but if your brake light switch is not set right, the brake light could be coming on too soon (too close to the 'no brake pedal pressure' position) and that would shut off or cancel the cruise control. That would explain your need for a bungy cord, if that is what you are doing with it, holding the brake pedal up. A way to check would be to see if the brake lights are coming on with little or no push on the pedal. As to the accel/decel inconsistency, I haven't a clue...

 

[KA6QGR]

Gerry i just got a new stop switch as well. How do i adjust this function?

 

[KA6QGR]

Gerry i just got a new stop switch as well. How do i adjust this function?

 

[GerryDrake]

adjusting the stop switch

I don't know on your particular one, but on the couple I have meddle with, they have external threads on the body of the switch and they mounted in a sleeve with internal threads and you just had to either slide it in the threads or screw it until you have something on the order of 1/4" of movement in the brake pedal before it makes the connection. I found that using a meter across the switch while adjusting rather than having the wires on it was easier, but then again, I don't know about the switch in your application. Perhaps someone here does and will chime in...

 

[Paychk]

KA6QGR



Welcome to the Forum



To adjust the brake light switch;



Push it through the clip in the mounting bracket until the switch is seated against the bracket. The brake pedal will move forward slightly.



Gently pull back on the brake pedal as far as it will go, the switch will ratchet backwards to the correct position and no further adjustment is required.



This is from the Factory Service Manual (FSM). Come on over to the 1st. Gen forum, a lot of great guys over there that have 99% of the answers... the other 1% we invent as we go!

 

[KA6QGR]

Gerry i had the Dodge service agency here do the instalation so i am sure they did it by the book but the bungy cord is still needed.

 

[KA6QGR]

PAYCHK as you can see i accepted the store's responcibility.

 

[cojhl2]

This smells like the above have said, It is the Brake Light switch. Even if it was installed by the DC shop that does not guarantee a thing.



The cruise control is aborted by a circuit made in that switch also, hence the connection between you observing braking action and cruise control malfunction.



The bungi holding the brake up to correct the situation means the switch is too far away from the pedal shank.



Is there something missing that lets the Brake pedal come back too far (like a rubber stopper) that lets the pedal push the switch out of the way.



How about the return spring on the pedal? If you look under the dash at the mechinism I am sure you cona determine what is wrong. Good luck,, hard thatn the dickens on the neck!!

 

[KA6QGR]

correction

I think that everyone is focusing on the brake peddil. I have been told there is no spring but the new master cylinder is the to pusl back the peddel. Now for the correction. With the bungy cord keeping the brake from disengaging the cruse control the cruse will accelerate or decelerate at will, ITS WILL. Usually when the system is warmed up. I traveled from Blythe to Phoneix about 150 mi and both happened at various times. No warning or pattern that i can find. One thing i just found seems if i put control at less than 70 it will hold under 70 mostly. Some actions of the road at times acts as a reason for disconnecting or decelaration and then the same rode condiitons will not cause this. I can not find too much for the accelaration. It befuddeles me.

 

[btoscano]

I don't know at all how the cruise "computer" works on these trucks but I do know the cruise "computer" on old Mercedes would do exactly as you describe. The solution was always to resolder the solder joints or replace the cruise "computer". I would suggest replacing the cruise "computer" with one from a junkyard and see how she works unless someone is more familiar with the problem specific to these trucks.

 

[Philip]

On your cruise problem. Lets start easy here. Unplug the connector on the cruise control head. Terminal #1 is the ground, this is the black wire. Check it with a OHM meter to the battery - terminal. It should show little resistence on the meter. If it is showing a high resistence clean the grounds.

 

[Paychk]

Just had some problems with mine, unplug/plug the connector several times fixed it. Adding some dielectric grease wouldn't hurt ether.

 

[KA6QGR]

paychk help me where is the plug?

 

[Philip]

The cruise head is located on the left fender well just below the grid heater relays. It is the round thingy. LOL

 

[Paychk]

The plug is on the bottom of the round thing that has a cable that connects to the throttle, and is where Phillip describes it above.

 

[cojhl2]

I just went out in the shop to check my brake pedal. I did not look for the spring, but I can definitly tell you it has one by the way ir feels.



That would make sense anyway cause you should not depend on the Master cyl to push the brake back. There should always be freeplay.