W124 Cruise Control amp question

[Richard Eldridge]

The amp on my 1990 2.5 300D Turbo went out last summer.

A trip to the U-Pull-It yielded the amp from a 1988 300E. Sold to me for $8.00 as a "Fan Relay Black Box", even though I told the cashier what it was.

According to FastLane, the 1988 300D used one of two different CC Amps. The one I seem to have is identical to P5002-63658, which is also used by the 1990 300D 2.5 Turbo.

It has 2 rows of 7 pins on the right side and has a small black device plugged into it with the numbers 03 88 / 007 545 12 32 / VDO 519.201/1/1/14
on it. This device has two rows of three pins each.

However, the numbers stamped on this device are entirely different.

These read 09/88
12V
412 212/1/1
(MB tristar) Mercedes Benz
005 545 05 32

There is also a blue stamp , an irregular hexagon with the numbers 528 09/88 in it.

I am aware that it is probable that in the 17 years since this thing left Sindlefingen, it has probably dies just as my 15 years one CC Amp died, and I therefore should consider resoldering it.

However, do any of you experienced MB techies know why the numbers stampre on this part do not correspond to the numbers given on FastLane?

I greatly appreciate your valued opinion and response.

[E300D]

Hello,

I dont have an answer for your question but someone will chime in for sure .



THe cruise control in our 95 E300D is cutting out as well. I think it has to be the cruise amp.

I want to repair it, I do not know however where the amp is. Can I drive the car without the amp?

I am slowly gathering info.

I found this site, may be very very useful:
http://www.mindspring.com/%7Ehoulihan/merc/cruise.htm

[moakesr]

I believe the module that plugs into the CC amp is what Mercedes refer to as a 'coding plug'.

I am pretty sure it allows them to use a generic CC amp, but 'program' it for different vehicles.

With any luck, your old coding plug should work just fine with the replacement CC amp you got, which I believe you say has the same part number as the original faulty item.

Richard

[kggkgg]

What are the symptoms that make you think its the amp.

Mine is also cutting out but I dont know if its the signal from the control stick, the road speed signal or the amp. How does one tell?

Keith

[Richard Eldridge]

You can drive the car without the cruise control amp. The cruise control just will not come on.

When a CC amp goes out, from time to time, with the CC on, the car will slow down and then speed up again in rapid succession. the car sort of bucks and wheezes as the CC cuts out and back in.

I suppose that it COULD be the other items, but everyone in here has mentioned only one cause: the CC Amp going out.

Apparently, after a certain amount of useage, the solder connections go dead and it won't function. I imagine that if they used a better type of solder (silver solder, perhaps?) this would not be a problem.


Then one day, the CC will just refuse to work.

The amp in the 87-92 W124 is screwed to a plate just under the speedometer, about an inch above where the lower dash joins the upper dash. It is screwed to a bracket with phillips-head screws that are very, very tight. It is easier to unscrew the 8mm bolts on the bracket. There are only two, and when you have taken them out, you can take the amp out with the bracket and unplug it from the harness.

I still don't understand the deal with the parts numbers vs the numbers stamped on the device.

[lrg]

Here's some info on CC diagnostices (at least for systems through 1992)

GDL Troubleshooting guide

You may want to pke around on this site a bit. It has a bunch off good info about cruise systems.

[speedy300Dturbo]

You can't use an early amp without the coding box provisions on your 1990 300D. You'll need to head back to the junkyard and find a CC amp out of a 124, 126, or 201 car that also has the black coding box on it. Put the coding box from your 300D on the junkyard CC amp, and you'll be good to go.

[Richard Eldridge]

You can't use an early amp without the coding box provisions on your 1990 300D. You'll need to head back to the junkyard and find a CC amp out of a 124, 126, or 201 car that also has the black coding box on it. Put the coding box from your 300D on the junkyard CC amp, and you'll be good to go.
=========================================================
Thanks for the advice.

Is the coding box the small black six-pin thing that the amp plugs into?
If so, there is surely one on the defective amp that is installed on my car.

It is my understanding that what always goes out is the amp, that is, the circuitry in the silver box, not the small coding box, if that is what the part is.

The 1988 unit has a coding box on it already, as I stated, assuming that the small six-socketed box is indeed the coding box. There were no other boxes in the vicinity, so I am pretty sure that that is what this is.

There was only one 300E and no 300D's in the junkyard. There are several 190's, but the year is not accurately indicated on the vehicles.

By the way, the number listed on the box is identical to the number listed by GDI. 005 545 05 32

I got this one with the idea that I could resolder it and save several hundred dollars. I also took it out so I could see what needed to be removed to get at the fool thing, which turned out to be a lot less than was mentioned in the manual I have, which starts with the steering wheel.

$8.00 seems like a small price to pay for a hobby. A brand-new, 2005 technology Cruise control with all the latest bells and whistles would cost a lot less than repairing the unit on my car, only it would be less convenient to use.

It cost me over $400 to replace the CC on my 1985 300TD, and I did all the labor myself.

Changing the box and the actuator isn't hard. It's getting to the box without messing up anything else that sucks.