ICQ>

If the oil level and the wiring are o.k. another root cuase might be wear of

the rubber O/D piston rings (mainly if O/D works fine when cold, but intermittend when warm/hot).

The O/D clutch is actuated by two pistons sealed with rubber O-rings.

If these rings are worn oil pressure is reduced when the oil gets hot.

The parts are very cheap, but you have to take the gearbox off the car to change them.

You might want to use a high quality oil in the O/D to avoid this issue until you are going to rebuild your gearbox. Castrol RS for four-stroke motorbikes worked fine for me.