I just bought a 1982 300d with 143,000 miles on it! The car is in great shape except for two things, the cruise control does not work and the tachometer does not work.</P>


Are they related?</P>


What is the first thing, or most likely cause of Cruise failure (the brake lights work).</P>

 

They are probably unrelated. Two major components of the cruise control system fail with some regularity. The amplifier is the electronic component and is the more likely candidate. The actuator is the mechanical component, and also bears some scrutiny. Both item are found under the hood.</P>

 

I have the same problem. I do believe that both of these items are related. I haven't figured out how yet but the tach and the cruise went out at the same time. I don't think it is a coincidence.

If anyone has any ideas please share..

 

Unplug the control components and plug them back in to re-seat the connectors. The tach amplifier is located on the left fender. It is a round black pod that unscrews. The cruise amplifier is located above the driver's feet. You have to remove the lower dash panel to gain access to it. They are not related. Also check your taillight/brakelight bulbs. Clean the contacts. The cruise control is very sensitive to voltage.

 

I'm having cruise issues on my 93 300SD. It feels like a mechanical issue, because it tries to hold the speed, but once the accelerator has to give much throttle to accelerate, the cruise just drops out. (i hope that makes sense, I'm not mechanic) Actuator?

 

p.s. this issue is gonna get me a ticket, i can see it already... even with a slight compression leak on glow plug #5, it has so much pickup for a diesel it's almost unbelievable.