Rail King GG1 Pantograph motor P/N

I suspect it's the same mechanism that is used for the Premier GG-1, have you tried calling MTH?  FWIW, the most common issue with those is the belt starts slipping.

PS-3 Designs have change, but principle is the same.  I agree, making sure belt not slipping, and also pantograph engaged properly.  You also can unplug harness and use 9V battery on motor to see if it spin.   G

Thanks for the information will try the battery

I run many GG-1 locomotives.  Do what George told you.  I run into that situation many times each year.  Hit the motor with 9 V in both directions and you should be OK.  I run many electric locomotives and have never had to replace a motor.  

Marty when pantograph belt slips do you just replace them? I have a bb1 and the mechanism is a little differ from the GG1 loco proto 2. Do you use a small O ring than a number 14? It also seems that the motor turns the wheel one way and it isn't turning the other way when pants go in other direction. Maybe it needs a reset too.

Yes.  Take belt off and go to auto store or home improvement and match up.  As example the PR GG-1 uses a 19mm 2.5mm belt.  When testing with battery does motor spin both ways?  I just worked on a PS-2 3v where the circuit board had a bad channel.  Only would spin motor one direction, not the other.

BUT slipping belt can look the same.  Going up is easy since spring helps motor or slipping belt.  Going down your fighting the spring and pulling panto down.  That is when belt will slip if expanded, or oiled up.   How about a picture of you mechanism and control board.  If this is PS-3 the board is new and very small.  Check for broken wires, but if it moves one direction that usually is not a broken wire.  G

George I think I have a problem with the pantograph board. Both motors only turn in one direction. Do you have these boards or part numbers?

AG-3100000 for the premier GG-1 PS-2.  G