GP7 Ground Relay tripping.

Our GP7 has begun to trip the relay quite often. It seems to happen most when changing run levels, say from 3 to 2, or down to idle. We can reset it and go for quite aways, until we change notches again.
How does one figure out what the problem is? We have looked for burnt/broken wiring in all of the cabinets to no avail. Whats a good way to diagnose this problem? What else can we look for? thanks. -pat masterson

The ground relay protects the high-voltage side of the electrical system. The leads to the motors, and the leads from the contactors to the generator are the main items to check. (with engine not running) If no signs of cracking, chafing, burning, etc are seen, you might also inspect the brushes and brush holders, both in the traction motors, and on the main gen. Unfortunately, sometimes you might not ever track down one of these little devils. With the loco dead, and switch pulled, you can also blast out the brush sections of the motors and generator, with some electrical cleaner, or safety solvent. Same for the contactors, breakers, etc. When we put the TP&W 800 & 801into service on the M&E, I used two 5 gallon buckets of safety solvent on each loco, cleaning out the electrical cabinet, and generators/t.m's, etc. That's how much it took, to clean out the cabinets and cases! It's a very dirty job, but it helps rid the unit of electrical gremlins. If you have the "can stand" controller, you might wanna open it up, and blast this out as well, as there's HV contactacts inside there, as well.