300sd cruise

[frossa]

1979 300sd, I can get the car to accelerate with the column stalk, but can not set speed. Which part is it likely to be ?

[Mike D]

It's usually the amplifier but check the vacuum diaphragm first. If you have a vacuum leak anywhere in the system it can affect the cruise supply line. Someone also mentioned their cruise wouldn't work unless ALL the doors were locked. Whether that was a safety feature or an indication of a vacuum leak in their door system I couldn't tell you.

[JimFreeh]

Originally Posted by Mike D

Someone also mentioned their cruise wouldn't work unless ALL the doors were locked. Whether that was a safety feature or an indication of a vacuum leak in their door system I couldn't tell you.

That's a deferred maintenance issue....

Your symptom sounds like a bad amp.
You could try the resolder trick, do an archive search for mucho info.

Jim

[Mr.Kenny]

Re-soldering my amplifier did the trick. All you have to do is hit every solder joint with the iron so it re-melts the old solder & makes a new connection. I don't remember if I added more solder........I probably did if the joint needed it.