The signature E36 top failure is mechanical, not electrical — and I catch this one all the time. Under load the sheet-metal bracket carrying one of the trunk gearmotors bends slightly, the motor's pinion stops fully meshing with the large gear, and it slips off.
What you'll notice:
- Ticking, knocking or grinding (loudest when the storage lid first tries to lift).
- Sometimes metal shavings.
- The top stalling partway.
- A flashing red light in the switch.
If the motor spins with a knock, or the top won't begin a cycle, I suspect the drive gears jumping mesh first, then the position microswitches, then the module and its wiring — a truly dead motor is far rarer than a slipping gear.
The lasting fix is to straighten and reinforce the bent bracket and re-seat the motor so the pinion stays engaged. Drop in a new motor without correcting the bracket and it just slips again.
For this you'll want the gearmotor and a reinforced bracket kit (and the microswitches if worn) — I've put them below.