Fixing cruise control on 87 300 SDL

[Turbopugsleylx]

Hey gusy the cruise on my car does not work whatsoever....regardless of which way I switch the stick thingie....what fuse is the one that handles this? all my fuses seem to be ok with no problems visually..though the Cruide does not work...

[compu_85]

If you hold accelerate does the car speed up?

-J

[Jeremy5848]

If the fuse is good, the next culprit is the electronic control, which lives in an aluminum box under the dash. You can search the forum for more information -- it's been discussed many times.

You can resolder the pc board in the box or buy a rebuilt from one of the on-line dealers. Caveat: most require a core (your old one) in return and will not accept one that has been resoldered at home. You have to decide whether you want to take that risk. Try this link for a source of rebuilt cruise amplifiers. Their core charge is in excess of $100, BTW.

The actuator on the IP is the next possibility. Buried under the intake manifold, it is much harder to access and fortunately fails less often than the electronic "amplifier."

Jeremy

[Turbopugsleylx]

The thingie is completley unresponsive regardless of which way I move it...accel decel whatever....I do not which fuse to look at to see if its good....is it a fude or a relay that handles it?

[Jeremy5848]

I don't know the S-class fuse lineup but there should be a list on a card in the lid of your fusebox that says what each fuse powers. "Tempomat" should be in the list somewhere -- that is what the Germans call cruise control.

[a2t]

Make sure the green wire behind dash is actually plugged into the speed sender on back of cluster, and into the transfer box. I replaced the whole module and found the PO had for some seemingly stupid reason unplugged that wire from transfer box. Took a bunch of pics and some old timers from here to tell me where the dangling end of wire went, back in dash on some block where several cruise signal wires plug into.

I got rebuild cruise amp for $160, now it all works. But before installing a new/reman cruise amp, test the actuator (its very easy) to ensure its not drawing too much current, or it will fry your new amp.

And make sure to change out those plastic rod ends on the cruise linkages with metal ones from a 123. Shortly after I got cruise working I may have uncovered reason why PO unplugged that wire. One of those little plastic ball ends popped off linkage and linkage jamed into intake at damn near WOT. NOT cool 'Mr bean counter who changed metal 123 part to plastic 124' dude. My wife and kids and front brake pads didnt appreciate the $.02 cost saving on flight critical component.