Did this job a year ago on my 1985, also got a refurb unit from Roger. I also did the testing of the input signals and tested the servo, there is a procedure for this in the WSM, pretty straight forward but good to check that the input and servo is working since a new computer will not fix the issue if there is a bad speed signal. A scope is needed to capture the speed signal, which is just a square wave, and I believe the servo can be refurbished with a new seal from Roger if it is leaking. Let us know how the new computer works, I actually never tested mine yet.
I have exactly the same issue. I had previously had the board re-soldered and the cruise came back to life. Although that was 15+ years ago, fix lasted for 10 years. I not surprised your reconditioned module did the job! Please open the old module and check it out, just for interest.
My '87 cruise does nothing. The engine vacuum system was a mess, broken pipes, perished rubber connectors and several breaks. Repaired all the breaks and pulled out the vacuum servo for the cruise and vac tested that and the solenoid, no change, so might be the control module. Bonus was repairing the engine vacuum provided vacuum to the auto transmission, it now changes smoothly instead of banging into gear like it always did.
While my cruise control works, it doesn't maintain speed very well. It lets the speed fall too far before then overshooting, and then the cycle of under and overshooting continues. I'm told that's just what they were like. I have a 1987 W201 Mercedes and its cruise control works much better, and holds the set speed quite well.
The replacement 928 cruise control unit from 928srus worked perfectly, cruise control is fully functional again!
Did this job a year ago on my 1985, also got a refurb unit from Roger. I also did the testing of the input signals and tested the servo, there is a procedure for this in the WSM, pretty straight forward but good to check that the input and servo is working since a new computer will not fix the issue if there is a bad speed signal. A scope is needed to capture the speed signal, which is just a square wave, and I believe the servo can be refurbished with a new seal from Roger if it is leaking. Let us know how the new computer works, I actually never tested mine yet.
I have exactly the same issue. I had previously had the board re-soldered and the cruise came back to life. Although that was 15+ years ago, fix lasted for 10 years. I not surprised your reconditioned module did the job! Please open the old module and check it out, just for interest.
Thanks for posting this. My cruise sort of woks but is intermittent, never when cold, and even when it does work sometimes it just quits.
My '87 cruise does nothing. The engine vacuum system was a mess, broken pipes, perished rubber connectors and several breaks. Repaired all the breaks and pulled out the vacuum servo for the cruise and vac tested that and the solenoid, no change, so might be the control module. Bonus was repairing the engine vacuum provided vacuum to the auto transmission, it now changes smoothly instead of banging into gear like it always did.
While my cruise control works, it doesn't maintain speed very well. It lets the speed fall too far before then overshooting, and then the cycle of under and overshooting continues. I'm told that's just what they were like.
I have a 1987 W201 Mercedes and its cruise control works much better, and holds the set speed quite well.
0:12 sounds like cruise control degraded into a dodgy launch control lol