Think you have a motor problem. My experiences with the motors is that in the end of the housing where the shaft exits the motor housing, there is a circular bushing in a groove in the casting that seems to be of a hard plastic material ? Still don't know how they got it into the casting groove... That bushing appears to have shrunk with age and binds up the shaft where it exits the motor. The motors armature actually turns quite fast, but the planetary gear reduction in the end housing reduces motor RPM's to less than 1 RPM. The end shaft I refer to only turns 180 degrees to open or close the buckets. In addition to supporting the end shaft, think it was meant to act as a seal to keep moisture out of the motors. The whole design with relays and limit switches can be quite reliable but... it depends on getting a full 180 degree rotation of the buckets so that the adjuster screw on the bucket mechanically operates the limit switches properly.
On that adjuster screw, a dissimilar metal condition typically causes a corrosion issue that likely has that slotted steel adjusting screw frozen in the bucket casting making it immovable, so a good long soaking of the screw with penetrating oil is needed to get it loose. Good idea to coat that screw with anti-seize when I replaced it after getting it freed up and cleaned up. This adjuster screw physically contacts both of limit switches.
With motors apart, I tried to use some emery cloth to try to shave a few thousandths off the ID of the bushing. That proved difficult and un-sucessful, so with the shaft in a lathe, I used emery cloth to just take off a bit of metal off the OD of the shaft where it passes thru the bushing, checking the fit periodically in the process so it rotated freely in that bushing without any binding. Little bit of lubricant also helps. things.
If operating the motor as a test on the bench, it must be fully back together with both ends of housing held together tightly as the armature of the motor depends on both ends of the housing to properly align and turn freely. I used a battery charger to operate the motors on the bench as they do draw a fair amount of current. In the car there is a circuit breaker located in the drivers side kick panel for the headlight motors and relays. The motors also have an internal thermal type protector that ultimately protects the motor windings. With motor not mechanically connected to the bucket, you also need to check that the bucket rotates freely and verify that your limit switches are electrically operating as intended.
