I've rewired a few 245 tailgates. Challenging and rewarding.

On my most recent one, I found I just needed to put in new good ground wires to set it all right. Each hinge has a wrapped harness of 4 or so wires, plus a separate black ground wire. The ground is just a short run, from one side of the hinge to the other. Especially for '88 and later, when they weren't using the rotting biodegrading wiring used in earlier years, there's a good chance that the very fine stranded wires in the multi-cable are OK and only the ground is broken. Look down into groove at top of hinges to see if the grounds are broken.

Installing new grounds 'original style' would involve removing the hinges which I never wanted to do. The method below is pretty quick and only requires removal of the tailgate's inner cover panel.

The grounds serve all tailgate functions. The metal hinge doesn't supply a reliable ground.

I drilled into the car body at the tailgate opening's side frame, near the strut mount location. I used a good sized stainless sheet metal screw, maybe a #10. Connect a ground wire there with a crimped on ring terminal. Run the wire down the visible hole in side of tailgate (at top). With inner panel removed you can fish the wire out at the bottom. You'll find ground screws near the center of tailgate near the latch. Connect your wire there. One wire on each side, to give good current carrying capability.

My thinking is, the motor may or may not be bad. But you must check those ground wires because if they're not good no other remedies will succeed. And it's a pretty easy fix.
--
Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.