Need help diagnosing cruise control 1991 300e

Hi,
A few weeks ago the cruise stopped working. Whatever it is that keeps it engaged isn't doing it.
Everything works except it won't stay on for longer than 5 to 20 seconds,
and then it shuts off.
Is this something easy to fix that I might be able to do myself?
Thanks for any ideas,
Aart
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Usually, it's cold solder joints on the small controller board. You can either buy a "fixed" board with an exchange of yours or, if handy with a soldering iron, fix yours yourself.

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It can also be a bad brake light bulb. I had this problem on my car twice. The first time it was the spring contact at the bottom of one of the bulb sockets. It just wasn't making good contact. I bent it back up and the cruise was fine. Then a year later one of my bulbs burned out. I replaced it, but the dealer gave me the wrong wattage bulb, and the cruise kept acting up. Once I put the correct wattage bulb in, everything was back to normal. I'd check these easy things before you go hunting for a cold solder joint on the board.
Bill Balmer 1986 190E 2.3-16 first 16V in the US featured in Car & Driver - March, 1986
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Hey guys!
Thanks for the tips. I'm amazed a brake lite could interfere with the cruise! I'll definately check out the easy stuff first.
By the way, where is the circuit board located that may have a cold solder joint or two? I use to be an ET in the coast guard so I know how to burn my fingers with a soldering iron.
Aart
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Check out these links:
http://gdl-online.com/begin1.html#contents (generally) http://gdl-online.com/remove.html (specifically MB 300E)
These guys are great. If you find you need to replace the amplifier, you'll not find a better source.
Rugbyguy

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