# Lessons Learned: Finding a Wiring Short



## LGB333$$$$ (Oct 11, 2017)

An interesting experience repairing a customer's LGB 2040 Crocodile Locomotive. I replaced both of the original clam shell motor blocks with new D type motor blocks. Converted the push-pin connectors on the master cable from the locomotive's circuit board that connects to the motor blocks at each end with a 5-pin connector plug. When tested prior to reassembly on my DC Test Stand, the locomotive's motor ran well in forward direction but in reverse direction the three rear lights and cab light would not light and the motors operated slowly, even at max voltage. This condition is usually a sign of a short someplace but I couldn't find it.....thought maybe the motor block was defective. However, when I was testing the problem about the fourth time after confirming the wiring to that motor block and lighting circuit board had no shorts, I happen to reposition the wire to the upper light unit and the motors jumped. I moved back the white sleeve around the bulb and, Bingo, I found the solder to the bulbs to terminals had fused together. No wonder I was getting a short! After I separated the solder on that light bulb's two terminals, the locomotive worked like a champ in both directions. Lessons Learn: When there's a short in your locomotive, it super difficult to fault isolate the problem. I thought perhaps the locomotive's main circuit board was failing. But then found the short by chance, a light bulb's terminals shorting out the entire locomotive in only one direction, i.e., when that specific light bulb would be activated.


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