Going to try and troubleshoot the cruise control... - PeachParts Mercedes-Benz Forum

IdahoMauleMan · #1 03-12-2009, 12:26 PM

1982 300D.

The cruise control works about 5% of the time. Another 5% it is 'twitchy', i.e. it grabs a speed, but then disengages, but then tries to regrab it a second later, etc. The other 90% of the time it just never engages.

I've been putting this off since I don't really care all that when I'm driving in the city, and I'd rather not try and pull the amp from under the dash. But I've got a couple of long trips coming up so I thought I'd try and give it a shot.

Going to start with the easy stuff first, so I have a question...

Today I was pulling off all the throttle linkages for lubrication. There is one bar that connects to the cruise control module in the engine compartment, right by the power steering filter.

The little arm on the cruise control has absolutely no resistance to movement at all, with the linkage off. It just rotates freely at the slightest touch.

I have no idea what's inside, but I guess I thought there would be a little spring, or something, putting resistance against the throttle linkage movement.

Does that sound right? Does this sound like a good spot to start troubleshooting the whole kit-and-caboodle?

leathermang · #2 03-12-2009, 01:07 PM

I suggest you check out the PerformanceProducts paper catalog and perhaps their website. They have suggestions on this and at one time allowed one to order the computer, put it on, check it out, and if that was not the problem return it in original condition... a very useful service in my opinion.
Also, you might find the FSM which covers this item... some things are harder to diagnose on a forum than others.. since tests are so specific and ordered.

IdahoMauleMan · #3 03-12-2009, 02:39 PM

Quote:

Originally Posted by leathermang

I suggest you check out the PerformanceProducts paper catalog and perhaps their website. They have suggestions on this and at one time allowed one to order the computer, put it on, check it out, and if that was not the problem return it in original condition... a very useful service in my opinion.
Also, you might find the FSM which covers this item... some things are harder to diagnose on a forum than others.. since tests are so specific and ordered.

Thanks. What is an FSM?

leathermang · #4 03-12-2009, 02:47 PM

Factory Shop Manual ....

dieseldiehard · #5 03-12-2009, 07:38 PM

here is a good resource for rebuilt CC modules etc.
http://www.fix.net/~gdl/begin.html

MaydayMike · #6 03-13-2009, 08:28 AM

After you price rebuilt cruise amps and acuators, you may want to think about this option. http://www.peachparts.com/shopforum/showthread.php?t=219993 Works just as well as the original setup, and if you're handy enough to change your own oil, you should be able to do the install in a few hours.