Cruse control mod
 

I've been trying to get my cruse control to work with no luck. I've perform all the test and with positive results. I'm able to set the speed but it doesn't hold, it starts to decrease slowly. I'm petty sure the problem is the control unit, if any one has a working unit for sale or one that they could loan me I would applicate it. I would be glad to send a deposit for the unit.

This guy:

Home — Cruise Control Repair

He is the man for repairing our cruise control units.

No offense meant to our host.

Yep, that is the control unit. Mine did the same thing. I sent it in, and had it repaired. Works great now.

And the Bentley manual has a glaring error on the test procedure for the switches.

Replace the 0,1 uF capacitor near the Guenther relay ( lower right side of the board when you hold the connector up ).
It is the capacitor that has ‘one leg up’ that is connected to the relay and to the BSV81 FET transistor. Protect the transistor from the soldering heat. Mind he polariy of the new capacitor !

While you are in there, you can also replace the two 47 uF caps in the middle of the board, but try to replace them with 47 uF of a higher voltage rating ( eg 25V) instead of the 16V max rating the factory put in there.

I will try replacing the capacitors, recently repair my clock by replacing the cap, I suppose they dry up with age. Thanks for the info.

Kris Rose, at the above mentioned website fixed mine and was very prompt, professional, and knowledgeable- highly recommended

Another vote for Kris Rose. Even though he wasn’t familiar with our auto temp controller between the seats he was able to repair mine after he repaired the cruise module. Both are working great.

Cruse control mod
 

Replaced the capacitors per Frank M. instructions, cruse control works. Thanks Frank

No worries mate !

I am trying to map all the electronics in my car just so I can service it for the next 35 years. The cruise control was my first (had the same issue than yours), have done some of the relays meanwhile as my dme relay failed (the original from 1984!) and the buzzer relay. Done the schematics on both of them and was able to fix them.