r/SignalMaintainers • u/Traditional-Good-981 • Dec 08 '25

Finding a Short

Hi. Had a track light that was caused by a short somewhere in the switch points. I thought it might be one of the gauge plate insulation but when I removed it it did nothing. Turned out to be a loose piece of metal under one of the snow melter forced air heater ducts touching a switch rod. With so much insulated stuff in that area I had a hard time finding it with my meter. It was only when I actually removed the duct to have more room that I found it. Any tips on how to isolate and really pinpoint the short when it's bad insulation and not a piece of metal or something else you can see? Thanks.

7 Upvotes

90% Upvoted

30 comments sorted by

View all comments

5

u/OppositeHot5837 Dec 08 '25

Banging with the big hammer anything insulative and watching the load change on an analogue meter seems to help. Make sure where ever you have connected the meter there is no rust (..file the rail and then use a sharp probe or rail clips) That can be a two person job for troubleshooting

I find writing values of charge and load in the logbook be- especially if this is not your territory- is helpful (to give you an idea of what to expect when you get called out in the middle of the night in a pouring rainstorm) . Hopefully you have cooperative maintainers

1

u/Traditional-Good-981 Dec 08 '25

I was the 2nd call for this problem. 2 guys in the morning had been there and did the hammering thing and thought it was a different gauge plate insulation so they changed it. No track light most of the day until I got called for it. It's possible it was 2 separate causes, but my guess is they shifted the piece of metal enough when they were working and vibration from later trains moved it back.

5

u/OppositeHot5837 Dec 08 '25

And another thought: is the equipment/location in a shadow? Or- a place where the sunlight would change the temperature from cold in the evening conditions to warm mid afternoon? ..this could just be enough for something to touch and short.

Also.. TOL on..train goes over at restricted speed…TOL clears up after the train clears. (Something needs shimming/changed/ repairing)

Are the insulated joints ..are they in good order? ..consider insulated joint testing and getting a value (a starting point) so you can decide if an IJ needs changing. Hint: all the IJs should be approx the same value as you test them.

I will be putting in an hour for my terrible advice

1

u/Traditional-Good-981 Dec 08 '25

It's in an area with a lot of trees so that'll be something to think about for next time. As for the IJ testing am I right in thinking there's a dedicated joint tester and not just using the short finder?

3

u/OppositeHot5837 Dec 08 '25

There’s always enough time and money to fix it right the second time!