87 300D - Cruise Ques, its not amp or actuator :( - PeachParts Mercedes-Benz Forum

a2t · #1 05-26-2007, 05:52 PM

No working cruise in my 87 300D turbo.

Tested actuator per GDL-online. Works fine. Replaced cruise amp with rebuild from Benz-store ($155, nice!). Still no flippin cruise.

What else could it be? I tested cruise stalk and it seems to work fine - basically probed the 14pin on cruise amp plug for inputs from the stalk. Worked just fine.

Also shorted wires from plug on amp to actuator to get it to move throttle, does it just fine.

Could it be the speed sender? Anything else I should be looking for?

Help me..the gas pedal has 10lb spring in it, lots of long drives killing me...

cdplayer · #2 05-26-2007, 09:50 PM

Since you covered the major areas, your problem could be as simple as mine was. A tail light bulb. Mercedes requires the use of Bosch or Oshram brand bulbs only. The system picks up a critical ground from the bulb because of it's design. Using the usual 1157 replacement bulbs you can find at most DIY stores, will in effect, cause the cruise to malfunction.

stevebfl · #3 05-27-2007, 03:18 PM

There is also a version modification on certain modules in that era. It requires removing a wire from the connector if I recall. Have no info at home, but there would be a bulletin on it if it applies to your car. Might search for it.

a2t · #4 05-29-2007, 11:30 AM

when you say tail light bulb - are you referring to brake light bulbs, or just the tail light bulbs ? Would front parking lights have anything to do with it? headlights? Hell while we are at it, reverse light? dome light? the burned out glvoe box light? Now I know why the cruise amp has 14 pins on it!

I checked all mine in the rear -

some say phillips, some osram, some just have a bunch of letters, digits on them.

Maybe I should just go to dealer and get all all new bulbs.

stevebfl · #5 05-29-2007, 11:53 AM

Yes, your car is affected by the modification. The actual document is AF54.18-U-6102A, titled: Cruise control does not operate after replacement of cruise control amplifier.

The story is such: A bridge is installed in cruise amplifier between terminal 13 and 14. Ground connection at pin 14 interferes with pin 13 signal. This is said to occur after amplifier 005 545 05 32 is replaced up to manufacturing date 08/88.

The remedy is: remove the bridge for ground between socket 12 and 14 in cruise control amplifier plug. Connect ground wire or wires to socket 12. Socket 14 must remain empty!

a2t · #6 05-29-2007, 10:20 PM

Thanks for that - when I called my dealer to get the cruise amp, they told me an adapter plug was needed.

But I got the amp from benz-store.com, and it is same p/n as the one I pulled out - 004 545 2432. I *think* dealer was tryin to sell new 005 545 2432 and that is the one that req'd adapter plug. But since Im installing a reman 004 545 2432, I shouldnt have to use adapter plug, or heed that service bulletin.....right?

For what it is worth, the cruise did not operate with old amp either. Man Im hoping for something like a bulb - anyone know if cruise is particular to brake bulbs, tail bulbs, turn signal bulbs...which bulbs need to be the Benz OEM ones?

Bio300TDTdriver · #7 05-29-2007, 11:17 PM

Working on my cruise. Wanted to be copied on this post.

Lycoming-8 · #8 05-29-2007, 11:34 PM

From numerous discussions about the bulb thing, it seems like it was just the brake light. It is rumored that the cruise control somehow needs to have a particular bulb or bulbs in place for when you hit the brake to kill cruise operation. There should be no other tie to the brake lights, and even the need for the Germanic bulbs is only a rumor.

The one thing I do find nice about the original bulbs is the chrome plating on the barrel, which resists corrosion so much better than the cheap brass domestic replacement bulbs!

Jim Beville · #9 05-30-2007, 10:33 AM

So the bulb type makes no difference? What is the most common cause of non functioning cruise control? Jim

a2t · #10 05-30-2007, 06:21 PM

the most common cause? probably the cruise amp.

I read about brake light bulbs on gdl website. unless you screw up and install a dual filament bulb, it seems any brand of mono filament will work fine for the brake light bulbs.

So...if I got working brake lights with monofilament bulbs, rebuilt cruise amp, working actuator, what else could it be?

Has anyone ever had to replace the speed sender? Id hate to drop another $70 or so on it only to find that isnt problem either...