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1995 E320 Wagon, 2002 S430
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595 Posts
Discussion Starter #1
CC refuses to work on my newly acquired 91 300E except intermittently on the freeway. And when it does engage the thing goes WOT (wide open throttle) and takes off LIKE A BAT OUT OF HELL! WHOA HORSEY I say as I quickly tap the brake pedal to disengage the cruise control immediately.

MY QUESTIONS FOR YOU ALL...

1. Has this specific symptom and issue occurred with anyone else' Benz of this era?
2. What did you do to fix it?
3. Does anyone think that the oven bake trick or re-flowing the solder joints on the CC amplifier would rectify this particular problem?

Also, I understand the CC amplifier is underneath and to the left of the steering column but others have struggled to find it. Is there a detailed post or page that shows the process of removal for the CC amplifier? Thank you very much in advance.

SOUNDQUEST

Thanks you guys.
 

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1991 300D 116,000m
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730 Posts
1. I have WOT issues with my CC as well under certain circumstances. Mostly when I hit the Accel button a couple of times or hold it for a few seconds to accelerate. However when it gets done with it's WOT, WAYY past the speed I wanted to be at, it immediately drops down to the previous set speed...so I'm at square one.

The only way my cruise works is when I get to the speed I want to be at and I hit set.....as soon as I feel the CC 'catch', I let off the stalk and it settles into the correct speed. But I have to feel it catch because if I let off too soon, it won't engage the CC. Stepping on the brakes and hitting the resume seems to work perfectly, it goes right to the speed I was at before.

2. Nothing. Mine sets and resumes ok.

3. I think it's worth a try. I'd definitely do it before buying a new one...and that is very unlike me.

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1178896-cruise-control-amplifier-removal-91-300ce.html

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1258279-cruise-control-amplifier-location.html
 

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Registered
1995 E320 Wagon, 2002 S430
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595 Posts
Discussion Starter #3
1. I have WOT issues with my CC as well under certain circumstances. Mostly when I hit the Accel button a couple of times or hold it for a few seconds to accelerate. However when it gets done with it's WOT, WAYY past the speed I wanted to be at, it immediately drops down to the previous set speed...so I'm at square one.

The only way my cruise works is when I get to the speed I want to be at and I hit set.....as soon as I feel the CC 'catch', I let off the stalk and it settles into the correct speed. But I have to feel it catch because if I let off too soon, it won't engage the CC. Stepping on the brakes and hitting the resume seems to work perfectly, it goes right to the speed I was at before.

2. Nothing. Mine sets and resumes ok.

3. I think it's worth a try. I'd definitely do it before buying a new one...and that is very unlike me.

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1178896-cruise-control-amplifier-removal-91-300ce.html

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1258279-cruise-control-amplifier-location.html
Very helpful reply, thank you. I will get in there tomorrow and "see what I can see."

If upon opening her up I don't see any visible signs of distress on the solder joints, I will bake her according to instructions here Oven Trick | W124-Zone.com - A Mercedes W124 Resource Site
 

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W124
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5,178 Posts
Same thing happened to my '88 300e. Driving home from work, I was bored and flipped the CC lever up to set and held it there for a second or two. The car took off same as yours and I tapped the brake to stop it. It repeated this operation until I switched the car off when I got home. The CC hasn't worked in my car for nearly ten years so I was really surprised when it took off. One of these days I will have to get the lower dash cover off for some reason and when I do I'll pull the amp and check it visually for cracked solder joints. Until then I won't do much more than every now and then see if the symptom will repeat itself.

Let's see; EHAs that dump raw fuel on the engine, CC that throws the car into WOT, wiring harnesses that will make the engine inoperable, how did Toyota get so screwed over a couple of unintended accel claims? MB must have pictures of the DOT commissioner in bed with barnyard animals...
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,400 Posts
how did Toyota get so screwed over a couple of unintended accel claims?
Maybe the folks at Audi should answer that question when 60 minutes (back in the 80s) reported unexpected acceleration, which turned out to be user error because the American consumer wasn't used to having pedals placed closer together for heel-2-toe driving. But the damage had been done and almost caused Audi to pull out of the USA market all-together until the B5 A4 chassis saved them in the mid-90s.

As for Toyota, they are a victim of their own product, for building in massive quantities and having lost touch with the customer. When is the last time anyone got excited over a Toyota, or the Japanese Cadillacs (Lexus)? My last Toyota was a Supra twin turbo, and they haven't build anything worth driving IMO since.

In other words, ultra reliable AND ultra boring. Lexus may claim to be competing against the European offering, but Lexus as a brand has failed miserably so far in Europe until they introduced the IS220d which does slightly better because its diesel powered. But still boring nonetheless. And Europeans are not mesmerized by the Prius either. VW has had diesel cars that are far more economical long before the Prius became a sensation in the US.
 

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1991 300D 116,000m
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730 Posts
Audi totally got screwed with sensationalistic journalism, I use to see the Audi 5000 in red when I was a kid and thought it was interesting for it's time. Toyota got a little taste of that last year, but I think their PR dept got it under control. I doubt there was anything wrong with either of those cars that stepping on the correct pedal wouldn't have solved.

It's the same as making a remix of Howard Dean's jubilation and destroying a viable candidate's chances. People are sheep.
 

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90 300E, 87 300TE & 406 Mog
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166 Posts
My 90 300E has the same problem, I am going to look at the speed sensor for the cruise which is apparently behind the cluster either on the back of the cluster PCB or inline to the speedo cable depending on year, I will get back when I have done it if it works or doesnt,
cheers Russ...
 

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2015 ML250 Bluetec
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256 Posts
The hall-effect speed sensor is in the speedometer on all 124-body cars (yours). If the radio volume increses/decreases with speed, it is working fine.
 

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90 300E, 87 300TE & 406 Mog
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166 Posts
radio volume increases and decreases hmm, cant imagine many 124's having the original radio, mine included, original is long gone, any other way to test it other than the ohms of the sensor? looking at my symptoms this would be the first thing to check I would have thought unless you can suggest something else
 

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2015 ML250 Bluetec
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256 Posts
The only things connected to that sensor on the '91 are the radio, outside-temp sensor, and cruise control. I have not heard of the speed output failing but I suppose it's possible, testing its output is probably in the FSM and you're probably looking at a square-wave output.
 

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90 300E, 87 300TE & 406 Mog
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166 Posts
that would be my guess too, maybe something to do with the original radio being removed? my outside temp doesnt work either, hmm you got me thinking
 

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2015 ML250 Bluetec
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256 Posts
Outside temp in-op is common, usually the display goes dark. The speed signal to the outside display ('90-up IIRC) is only so that the temperature changes more slowly when the car is stopped or moving very slow (such as in traffic) so that it doesn't just read road temperature.
 
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