possiable short

[taraskirby]

Our BH loco stops working when the front wheels touch the track. This just started today.

[Joe Zullo]

It sounds like your pilot truck has turned backwards. Turn it around and you should be OK. BTW, there should be a little plastic insert with a white arrow on it that indicates front. It is seen on the bottom of the pilot truck.

[Loco Bill Canelos]

Here is a link to the instructions, You can see a picture of the front truck with the arrow if you scroll down to page 9 or 10.  Some of the very early Bi9g Haulers did not have the arrow, but no matter just turning it around 180 degrees as Joe says will fix it  :

http://www.bachmanntrains.com/home-usa/dwg/dwgs/Big_Hauler_Instructions.pdf

[Barry BBT]

Sometimes the arrow block will fall out, so you need a new spacer, glue it in place.

A little hint, paint the trailing edge of the pilot truck frame (and maybe the axle insulator) in white paint.  This way if you see it from the front you will know it is reversed and will short out the loco.

Barry