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'91 C124 300CE, '06 W164 ML500, '00 BMW MCOUPE, '65 COBRA REPL.
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547 Posts
Discussion Starter #1
Hi all,
as title states, I have an issue with my cruise control. It does not work at all.
I have read most threads, but can't find a solution.
My cruise control does not function at all.
I bought the car like this.

My car has the M104.980 motor. This is the 104 motor with the first gen. fuel injection. The CIS-E. So I think this will be closer to the M103 motors. Not sure.

Well, I have removed the c.c. amplifier (tempomat) and checked all soldering points. I even re soldered some. The unit has a slight smell of a shorted electrical board. Not sure if this is normal, just mentioning it. I do not think the amplifiers are prone to self destruction.

All the fuses in the engine bay, left of brake booster are good. I checked all relays in that area and nothing seems bad.
I also removed and checked the cruise control/engine overload relay behind the battery. Again seems good.

On a side note, my factory alarm does not work. I get voltage to it. Mentioning this just in case there is a common link, although I doubt it.

I do not think that my motor has an idle speed control module around/under the intake or anything that might affect the c.c. I could be wrong.

Is there somewhere else I should look?

Here is my engine.
 

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Registered
'91 C124 300CE, '06 W164 ML500, '00 BMW MCOUPE, '65 COBRA REPL.
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547 Posts
Discussion Starter #3 (Edited)
Thanks cbc atl, (thanks for all your efforts on having all these pdf available to us)
I am wondering where can this problem stem from as my brake lights work perfectly.
I checked all the lights last night and all is good.
I can see that the stop lamp switch can be my problem since it affects the c.c. and alarm.
But the stop lights work!!
I will check it any way.
Any other suggestions?

Thanks guys
 

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'89 420SEL, '93 300E and '07 Hyu Santa Fe
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562 Posts
I was having issues with CC in 300E as well. All lights was working but exterior lamp thing will pop up sometimes. One day i removed tail light assembly at night and surprise...My brake light bulb was lighted but very dim as much as that i could not see it in day light.
Thought about it and decided to check brake light switch at pedal, it was not looking right so Ordered on Ebay..Replaced it in 5 min and my cc works....

Anyone having cc issues first thing to check because it's cheap and spring in it may be gone by now
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,745 Posts
The problem is the cc amp. It is a well documented weak point. Just bite down hard and get a re-man unit or grab one from a pull it yard.

Good Luck,

Jayare
 

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Registered
'91 C124 300CE, '06 W164 ML500, '00 BMW MCOUPE, '65 COBRA REPL.
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547 Posts
Discussion Starter #6
OK I pulled the lower part of the dash and got to the brake switch. Works perfect.
Spring is good, and I do get the "interruption" of current on pin 8 on the amp.

For now I will assume the c.c. amp. is bad and get another one.

Thanks guys.
 

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Premium Member
'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,388 Posts
Or...do as Jayare suggested and send yours in (as a core), for a re-man with a warranty. But, since you soldered on yours now, they won't take it. However, you can still pull one at a yard and send that one in.....providing that no one soldered on that one either.:rolleyes:

Kevin
 

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1991 300E
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601 Posts
1991 Mercedes > 300CE > Electrical & Vacuum > Cruise Control Amplifier core deposit $65, price $181.17

"Part Number 0235452132, Programa (OE Rebuilt), Cruise Control Amplifier; Updated Amplifier Unit
"This unit is the Mercedes replacement unit for numerous older versions. Will require appropriate Mercedes coding part for proper function and may require slight wiring modification on some models per Mercedes TSB. Most failures are found in the coding part not the amplifier, we cannot accept amplifier return for warranty without corresponding proof of purchase of new coding part from Mercedes. 1 per car. "

You should call them and see if your re-soldered core will work. If not, you might find the cost/benefit of obtaining a junkyard alternative, plus shipping, to be prohibitive.
 

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Registered
'91 C124 300CE, '06 W164 ML500, '00 BMW MCOUPE, '65 COBRA REPL.
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547 Posts
Discussion Starter #12
Thanks Fish.
Mine looks just like when I pulled it off the car. The re soldering are not noticeable and should not be a problem.
I will check them out.
 

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'91 C124 300CE, '06 W164 ML500, '00 BMW MCOUPE, '65 COBRA REPL.
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547 Posts
Discussion Starter #13
Just an update.
I removed one from the local wrecking yard (yeah, I like going there once in a while, reminds me of when I was restoring a '78 Fiat 124 spider about 20 years ago).
The donor car had 316k miles so I thought it would have had it replaced, especially since it had a "Department of Defense" sticker.
I was right! It was replaced in '04 and works great and for only $10!!
Good times....
 
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