How do I troubleshoot a non functioning cruise control. Does the cruise require vacuum? Is the vacuum supplied by the engine vacuum pump or the auxillary pump in the trunk of the car?

Lots of info on trouble shooting cruise controls is at these 3 locations:

1) Archives - do a search on 'cruise control' - dozens of threads.

2) http://www.mbca.org/pages/tech/MBCA_Troubleshooting_cruise_cont.htm

3) http://www.gdl-online.com/begin1.html#contents

Good luck.

__________________
John

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

Click to see 87 300E

No vacuum on 1982 300SD Cruise Control. Electric servo motor and electronic control unit for it. 1).Make sure your brake lights work. 2). Check servo motor as per GDL techniques listed by JCE. 3) Remove Cr. Co. ECU and check circuitry (as best you can). 4) Send to GDL for exchange.

__________________
The Golden Rule

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