Robert

Just put the battery on my bj8 to test all the electics and had the same problem, I had previously cleaned, greased and rebuilt it. Had to take the glovebox out to get at it again which was a pain. Regardless off negative or positive cars, on the bench, attach the + of a battery to the terminal 2 (was green wire) then attach the earth E and terminal 1 (was black / green) together and to the - of the battery to see if it works.

Terminal 1 is the internally limit switched contact for the park control from the plate in the gearbox.

My problem was that on reassembly the commutator was to tight against the case on the opposite side to the field windings.

To check the motor undo the 2 long screws on the top (terminal end) and prise off the top, check to see the commutator spins freely, checks the brushes, you may the need to remove the 2 screws in the body that lock the field windings to the body and pull off the body, you can then check the windings with a meter and visually. When you put it back together make sure it again spins freely (the motor body has a slight recess that only goes part way down inside, so make sure it is the right way up).

Dried grease in the gearbox may also be to blame, clean and regrease.

It doesnt take much pressure to stop the motor turning!

Hope that helps, cheers Andy