My cruise control became intermittent and then failed completely. (1991 300D)

The problem was a broken wire on the clutch coil inside the actuator. The way that it is soldered to the circuit board allowed the wire to fatigue and break.

If you have a similar problem just check the actuator on pins 6 and 7 as marked on the plug. Use a meter designed to check diodes and put the positive lead on pin 7 and the negative on pin 6. If you don’t read a diode drop (.6 volts) then you most likely have the same problem

Thanks for such good advice

This sounds exactly what I have 1990 300d

Would you please tell me where I can find the actuator. I am very unfamiliar with this area of the car.

Many thanks

John

The actuator is mounted on the drivers side of the intake manifold and has an arm on it that pulls on the throttle linkage. The square plug that is mounted on the drivers side about half way down in the engine compartment is the lead that you can use to check it. You will have to look closely to read the pin numbers on the plug.

If you don’t get a reading on pins 6 and 7 you will have to take the actuator apart. There is a small tab that you will need to grind off with a Dremel tool in order to open it.

If you need more info I can post some pictures.

Thanks Tasma for the info and the offer of pictures, yes please, it will prevent me getting the wrong piece in hand.

Regards

John

I don't know how to post pictures on here. Maybe someone can help. I could also send them via e-mail if you send me a message at trceng@iserv.net

Also, when removing the nut on the lever arm of the actuator, "back up" with a wrench or pliers on the lever arm, so that you don't put pressure on the internal plastic gears.

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Thanks for the further tip. I will bear that in mind!

Re posting images here

I see that there is a grey button browse to an image in this reply form below.

If you wish to send a picture with a message click on Browse and navigate to the image you wish to send.

Select the image.

This will include your image in the post.

There is a mazimum file size allowed of 66560 bytes. Check your file size first to make sure its less than 66 kbytes.
I hope this is all clear

Thanks again for your help

Regards

John

Here is the actuator

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Here is the plug

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The pins to check

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Fantastic! and what a clean engine!

A picture is worth a thousand words

Even I cant make a mistake now! I think!

Very many thanks

John