Cruise Control Amplifier or Actuator???
 

Hey All,

Seems the cruise controls are always breaking. I have an '84 300SD.

Cruise Control sometimes works, sometimes does not. Also it only is smooth going up a hill or on an even incline. The car will "pulse" when the cruise is working, and when I am going downhill.

I have seen how to replace the amplifier, but not sure if my problem is a bad amp or an actuator?

Any suggestions?

Thanks in advance

Could just be dirty linkages. You need to remove, clean, and lubricate all the ball & socket links under the hood. That helps a lot. Usually when the amp dies it just won't work at all, or intermittently. I get some surge on downhills but not uphill, and rarely on level ground.

HTH,

Check your speedometer cable. After I fixed my Cruise Control (replaced amp) it was surging no matter where I was and I noticed my speedometer needle would jump around erratically when it was surging. After I checked and replaced cable all was fine and smooth. You may just have to clean cable and make sure it is secured and not flopping around loosely.

Here's a detailed check proceedure for your actuator. From the sound of it I'd guess you have a bad amplifier but do the other checks first. I've had to replace the cruise amplifier in both my cars.

How to test your cruise control actuator


The guys who provided the above testing proceedure also rebuild amps and actuators. They did both of mine and I've had no problems since. Good luck.

LRG