Cruise Control/TurnSignal Interaction
 

Today, Cruise Control (CC) started acting strangely. Stalk functions perfectly normally; i.e. set, accel, decel, deactivate and resume all function perfectly normally. However, whenever I put either turn signal on, the CC shuts off just as if I hit the brakes, clutch or deactivated it from the stalk.

Two possibly related things: One, minor front end damage on left was just repaired. Wiring was not disturbed in that area and all looks and functions normally.

Two, replaced all brake bulbs with LEDs (for lower latency.)

Any ideas?

CC Turn Signal Issue Solved
 

Solved!! Replaced two (of six) high stop bulbs with original 194 (W5W) incandescent bulbs. Problem resolved. Went back and forth twice and duplicated problem and 'cure' each time. Also left all LEDs in high stop and replaced one main bulb with original 1157 (W5/25W) bulb. This also resulted in correct operation. Apparantly, the CC system needs to 'see' incandescent bulb type resistance for it to work properly. This may actually be designed into the system to alert driver to failure of ALL brake lights. Not sure how the Turn Signals tie into the issue, as the Bentley manual electrical diagram does not show ANY connection between the CC system and the Turn Signals for my 97 318ti. Any one brake light (main or high stop) must be an incandescent bulb or there must be an equivalent resistor in the circuit. Only reason I suspected this is because a mechanic once told me that a GM car he was working on had a similar mechanism to alert the driver to a failed High Stop bulb failure. In that case the entire CC system stopped working when the high stop bulb failed and there was no connection to turn signals.