Thanks, but if you read my post changing over to dcc is not in the budget, and as I further posted, I solved the problem in both the dummy engine and the track issue. Both of the actual power units are pulling well again.

Thanks Johnathan, but switching over to dcc is not an affordable option right now. I did discover that running a dcc equipped loco (bought separately) on my layout was one of the problems I was experiencing. It eventually burned up the decoder so I gutted it and basically made it a dummy loco (or rolling stock). I bought another identical train set, added it to the manifest, and purchased the larger controller (MRC Tech 7), 18-23 volts, 2 amps). All worked well until recently. I sent out a request for help on a model RR group site I joined, and after checking several suggestions on troubleshooting, I found several sections of loose track that was intermittently losing power (I never secured it or ballasted it because it is hidden inside the tunnel), and further investigation revealed an intermittent short in the dummy engine where the pickup wires were grounding on the frame. I made repairs to the track and isolated the wires in the engine. The train has been running well since then with no overheating issues in the controller or either of the 2 power units. Thanks again for your response.

I have been trying to run multiple GP40's on my layout from the start. I have a relatively short manifest however I really like the look of 3 loco's. I have speed tested and matched them, and have also upgraded my controller for higher output. The problem is that they run good for several weeks and then one of them will start dragging the other one down. How can I correct this problem so I can run more than 1 loco and pull my full manifest of 16 cars which includes a track cleaning car?