OKay, here is a stumper for all of you technical types...

1978 W123 300D

Please explain why the cruise control on this car works perfectly at temperatures above 85 degrees (air temp.), intermittently between 75 and 84 and not at all below 75. Honestly, this is the truth. I've watched this thing do this now for two years. Any ideas? My MB mechanic would just like to replace everything...

Cheers

Jeffrey