Thread: Cruise control inverter schematic

I recently had to dissect the inverter unit used in pre-Bosch cruise control systems (RRC, early p38 and D1). This device seems to be an afterthought to convert the grounding SET & RES switch outputs to active 12V signals to the CC ECU. The ECU could have easily be changed to accept active low signals, but that's not the LR way.
My fault was the commonly reported dry joint and a picture showing this is attached. A re-solder was all that was needed.
In the case of more serious internal inverter issues, I've traced out the schematic for those inclined to diagnose and fix simple electronics. Note that there is no ground wire to the device. It relies on an open-collector output from the transistor to operate and is 'grounded' through the ECU inputs. The same circuit is duplicated on the PCB for SET and RES switching.Hope it helps someone.
Cheers,
Steve