I have a cruise control that does absolutely nothing. I pulled out the amp and checked resistance on the coding plug and every resistor is open. Every PIN combo tests open?

So I ordered a new Coding plug. But that makes mewonder what blew the "plug" out?

Any ideas what takes the plug out?

Here's an excerpt from "another parts dealer" about the amplifier replacement:

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.

That's the only place I've heard about the coding plug being a big problem. Elsewhere it seems that the Amp is a bigger culprit? I'm going to check the other parts, just thought maybe someone would say "X" makes the coding Plug Blow.

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<<Les Garten>> 1988 300TE 280,000 Miles

There is only one resistor in the coding plug that could possibly be blown by 12 volts. All the others are too high a resistance. Take the cover off and check across each resistor individually. Pry the cover out slightly to clear 4 small tabs and it comes apart easily.

What type of ohmmeter are you using and on which range?

That's what I did. I pulled it apart and checked all the resistors at the solder points and then because of my disbelief, I checked them all at the legs of the resistors.

I have a Fluke 87, that works perfectly on auto ranging. I have the tone on and can't get a beep or anything. The Fluke, I use daily, so no question there.

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<<Les Garten>> 1988 300TE 280,000 Miles

Pretty hard to believe. They are hysteresis and feedback for op-amps - unless the car got hit my lightning, no way they are open.

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86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm

Heh, well that ain't what my DMM says!

Very strange indeed.

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<<Les Garten>> 1988 300TE 280,000 Miles

You can't check high resistance with the beep on with a Fluke 87. It stays in the lowest resistance range. It is for continuity checking only.

Hey,
Thanx, I've had that thing for over 10 years and didn't know that! You're right though.

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<<Les Garten>> 1988 300TE 280,000 Miles

OK, circling back to this thread. I have a Fluke 87 and it was pointed out to me that if I turned the "BeeP" on, I would have troubles measuring high impedance. Sure enough. So now I need the specs for the coding plug I have. The plugs have greatly different test impedance's. I have Alldata, but it does not have specs for my coding plug.

I have 007 545 1232

Do any of you guys have the test points and measurements?

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<<Les Garten>> 1988 300TE 280,000 Miles