[valiant67]

It doesn't hurt to leave the cruise control switch on when you don't use it.
The speedometer cable comes in to the unit from the transmission then out to the speedometer in the dash.
Pull off the electrical cable on top and clean any corrosion, I doubt that's your problem but it's given me problems there before.

 

[Bob Lincoln]

Cruise control will not engage below about 35-40 mph, that's normal, and that's what the owner's manuals and literature have always said. Not enough vacuum to sustain it.

The acceleration sounds like a problem with either the servo or the cable.

 

[TWX]

I'm surprised it still works at all. The diaphragm in the module under the hood is a weak spot, and when it fails it just doesn't work any more.

 

[valiant67]

The only car I ever drove where the cruise sped up like that was my mother's 1978 Ford LTD. She bought it used after her 1977 was totaled and I don't think my parents every used the cruise in it so they never tried to have it fixed.

 

[AllanC]

I'm driving, I press the button at a low speed, maybe 30MPH, nothing happens. I speed up to about 50, and press the button, it engages! it immediately starts going faster.....55.....to 60...to 65.. then I have to turn it off because I'm on the streets! I can physically feel the pedal going down when this happens.

Do you mean the vehicle keeps accelerating and never reaches a speed where it stops accelerating? If the answer is yes check the slide switch on the turn signal lever for the cruise control. It has positions OFF, ON, Resume. Is the slide switch sticking in the Resume position? The Resume position is a momentary contact position. When you slide the button to the Resume and vehicle is above 30 mph and a previous speed has been set since ignition off, the cruise control will remember previous speed setting and return vehicle to that speed. When you release this OFF, ON slide button the switch should return to ON. If it sticks in Resume that might be the cause of the inintended acceleration.

I checked a service manual for 1984 K cars. Chrysler was still using a mechanically controlled cruise servo at that time so it probably is the same functioning unit used in your 1977 Cordoba. Service manual indicates to close the throttle completely. Pull and remove all slack in the cruise control cable by moving the cruise cable servo clevis towards a closed throttle position. There should be 1/16 inch clearance between the end of the cruise cable servo clevis and the stud on the thottle arm. If clearance is incorrect loosen the cruise servo cable clamp in the vicinity of the throttle arm and adust accordingly.

 

[TWX]

Do you mean the vehicle keeps accelerating and never reaches a speed where it stops accelerating? If the answer is yes check the slide switch on the turn signal lever for the cruise control. It has positions OFF, ON, Resume. Is the slide switch sticking in the Resume position? The Resume position is a momentary contact position. When you slide the button to the Resume and vehicle is above 30 mph and a previous speed has been set since ignition off, the cruise control will remember previous speed setting and return vehicle to that speed. When you release this OFF, ON slide button the switch should return to ON. If it sticks in Resume that might be the cause of the inintended acceleration.

I checked a service manual for 1984 K cars. Chrysler was still using a mechanically controlled cruise servo at that time so it probably is the same functioning unit used in your 1977 Cordoba. Service manual indicates to close the throttle completely. Pull and remove all slack in the cruise control cable by moving the cruise cable servo clevis towards a closed throttle position. There should be 1/16 inch clearance between the end of the cruise cable servo clevis and the stud on the thottle arm. If clearance is incorrect loosen the cruise servo cable clamp in the vicinity of the throttle arm and adust accordingly.

I wonder...

My '95 Chevrolet Impala's cruise control stalk isn't identical to the stalk in my '78 Cordoba, but functions the same. Slider and button on the end. Since the Cordoba uses a Delco steering column, I wonder if they also used a Delco controller, and if so, if that would mean there could be aftermarket non-Mopar parts that might let one's cruise work again...