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Runaway cruise control on '86 900S Posted by Baab [Email] ![]() ![]() ![]() |
I've been working on my '86 900S cruise control trying to get it working. Basically I found the vacuum lines were bad and the cutout switches needed adjustment. After fixing these, it works in a way -- when you hit the "SET" button the car just takes off and keeps speeding up, just as though you were holding the button down or flooring the accelerator! Hitting the brake disengages the cruise control for a few seconds, then it comes right back on! (Needless to say I'm going to remove the cruise control fuse until this is corrected.)
I don't know the history of the car, but it looks like the turn signal/cruise control switch was replaced fairly recently, it has been spliced into the original connector and appears to be working OK. I assume the speed sensor on the speedometer is sending out a signal, or the cruise control wouldn't engage at all. The vacuum pump passes the electrical tests in the Bentley manual for disengaging.
Any ideas what might be going on here? Bad control unit? Sticking relay? I do notice the Bentley service manual manual says on pg. 368-4 that when a new-style control switch is installed in an '85 thru '88 900, it is necessary to remove a relay and splice two wires together in the relay connector. I can see that this has not been done -- how can I tell if I have a new-style switch? Would installing one and not doing the relay modification have this kind of affect?
posted by 66.217.67...
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