Cruise control and Tach problems on 300SD
 

I have 2 300sd's an '82 and '84. Both have the same problems. The tach is dead and on one the cruise wont lock in, it will accelerate but wont lock, on the other it will lock and work fine then it will start to accelerate and/or drop off. I have done the obvious by lubricating the linkages and cleaning the electrical connections but didn't help. Also what is a good repair manual for these cars? Haynes was pretty useless.

On the one car the tach gets a signal from a special box on the diesels that generates a signal from the crank sensor - that's probably out. As for the cuise it's the same old thing 99% of the time it's the cuise amp has died from bad solder joints. (are you glad new cars have more gadjets?)