Ok, I found out my cruise control actually works... ACCELERATE and DECELERATE works like a charm, as well as SET SPEED (?)... anyway...

I do not know how the cruise control mechanism actually works, not knowing is what's bothering me.

CAN the cruise control malfunction in such a way that I lose MANUAL control of the accelerator?

Let's say the SERVO or whatever controls the linkages (if ever) gets stuck or is given the wrong signal to continue accelerating can it be OVERRIDEN by the pedal? IF there's a slight chance that it can cause me to lose control of the pedal then I AM gonna disable it. I do not want to rely on a 25yr old system.

Thanks.

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

The brake switch cuts off power to the servo.

What if that fails? Is the servo "stuck" at that position? Are the linkages spring loaded such that when the servo is cut the linkages return to normal position?

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

There is a clutch in the servo that must be powered for it to remain engaged. When power is cut the actuator springs back to its resting position.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

It's more likely the floor mat will wedge the accelerator pedal at WOT, even if these aren't Lexus

Sixto
87 300D

My previous cruise "amp" had a mind of its own. You would be going down the road fine, then suddenly it would decide you needed to be going 30 mph faster and would floor the go pedal to get there! Hitting cancel would not stop it, but pressing the brake would. It got my attention the first time it did it!

-J

Where do you use cruise control in Manila???

Mine sets itself about 10% higher than the speed at which you press SET. Accelerate to 57, hit SET, cruise at 65. Accelerate to 65, hit SET, cruise at 72. Coast to 65, release stalk, accelerate to and cruise at 72.

Sixto
87 300D

The amp I just got off ebay (same PN as the one from my car originally but made in late 1992) is working perfectly

-J

We were going north to subic. The North Expressway and the SCTEX hiway system has been improved dramatically. Reminds me of the I5... MUCH LOWER speed limit though... 100kmh?!?!?!?! I did go over that by 30kmh... the patrols didn't mind.

So the cruise is SAFE granting power can be cut off the actuator via the pedal... what if that cut-off system fails? Remember, I do MOST of the work in my car... so I'm on my own with regards to the CC. Anyway... maybe i'm just being paranoind. Cool that it works, just wanted to know how the system worked so I know how to troubleshoot and what to expect just in case.

I didn't notice that it was directly connected to the pedal... so worst case scenario IF it gets stuck at wot or part throttle... I just YANK the pedal back up?

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85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

In the cruise unit there is a relay which is connected right to the brake light switch, as soon as you touch the brake system it disables the cruise at a very low level.

I don't think pulling back on the pedal would do it. You could quickly cycle the ignition key.

To be honest I'd worry more about the turbo blowing and causing a runaway then the cruise control messing up and causing a runaway.

If you want to learn more about how your cruise system works, you might be interested in the GDL site....lots of useful information.

General Development Laboratories - Table of Contents

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Yes, but this is assuming that the switch will work...and after that, that the actuator will actually disengage. I'm thinking worst case scenario... where the cruise control engages and moves the linkages and locks up in that position... I guess my QUESTION really is... CAN THIS HAPPEN? I do not know how the servo/actuator is designed/assembled... what moving parts are connected to whatever. If I knew what the innards looked like I could probably make a sound judgement call.

Knowing how a semi-auto pistol works can save lives... by not assuming a gun is empty simply because the magazine is out.

__________________

85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

Your throttle linkage can stick even if you remove the cruise actuator.

You're more likely to run into Abu Sayyaf in Zambales

Sixto
87 300D

HAHA! I'd want neither. So everybody swears by it eh? Just be thankful that it works?

__________________

85 190E 2.3(SOLD)
86 230E (-->300D) sold
87 300D (-->300TD) sold
68 250S w/ a 615 and manual tranny (RIP)
87 300TD (SOLD)
95 S280 "The KRAKEN" (Turbo 2.9 602 transplant) traded
86 190E 2.3... current project

Well if any member had heard of a true runaway even once with a vintage mercedes. That is one caused by the cruise conrol system he could not get shut down it would have been mentioned on site.

Cruise controls of many types develop defects that make them surge higher. I have experienced this myself. Just cancelling them stops it though in my experience. Not brand specific either.

You probably have a much better chance of winning a major powerball lottery that the senario you project actually occuring. Or the chances of a steering system failure statistically is higher. In otherwords it is a very low probability issue.

There are other things just as serious that are more likely to occur. Life has certain unavoidable risks that are unpredictable as well unless you do nothing.