What am I seeing? (electrical problem)

[FiatFan]

I tried to run the train the other night after about a two month absence. Nothing. Started testing with the meter and eventually found that the two rails are showing a short. I have a single loop of track. No turnouts or other wiring complications.

A digital meter shows a short with about -500 ohms with the common lead on one rail. If I switch leads the meter shows open. With an analog meter I show about 500 ohms regardless of which lead is on which rail.

The track has been in place for about one year. It's brass, code 332, with plastic ties. I have vacuumed the ballast out from around the area where the problem seems to be occurring. I narrowed the problem area down to this location by raising the track onto wood blocks and then removing the blocks one at a time until I found the location where the short reappeared.

Some times if I move the track, the short will disappear, only to reappear a couple minutes later. I have put the meter on the track while raising the track and the meter still shows a short. If I remove the leads and retest a couple minutes later, the short is gone.

I am completely stumped by this behavior. Any ideas or suggestions would be greatly appreciated.



Tom

edit to add: I did not have the power supply connected when testing the track.

[Sumpter250]

I did not have the power supply connected when testing the track.

or -- any rolling stock or loco ????

"I have vacuumed the ballast out from around the area where the problem seems to be occurring. I narrowed the problem area down to this location by raising the track onto wood blocks and then removing the blocks one at a time until I found the location where the short reappeared." ---So, all your ballast is loose, not glued down ? maybe you should remove it completely for a foot or two either side of where the apparent problem is, and see if the problem "stays away".
Have you ever used steel wool for anything on, or near the track ?, or anywhere else?, since the last time things were working properly. My thought here is, something like a steel wool fiber, carried to the rails by a shirt sleeve, or by a piece of rolling stock that might have been set on "the source", "making contact with" brass rail could cause the resistance readings you saw. There is also the thought that the short might be "chemical" in nature....something spilled, dried up, but still conductive.

"A digital meter shows a short with about -500 ohms with the common lead on one rail. If I switch leads the meter shows open. With an analog meter I show about 500 ohms regardless of which lead is on which rail." --- That, is a bit odd, but the 500 ohm reading seems to indicate "contact resistance" between the rails, and the "cause" of the short.

In any case I can't do too much more than to "go on shooting in the dark", so I wish you luck "finding the gremlin".

[FiatFan]

Hi, Sumpter.

I use a 3M red plastic scratch pad for cleaning the track. The power pack is disconnected from the track and all rolling stock is removed from the track.

The ballast is loose and I have removed about 5 feet so far before the sun got to the problem area. (Can't work in the sun due to prescription drugs I am taking.)

Right now I'm pretty stumped myself. I guess I'm just going to start cutting the track in smaller sections until I isolate the problem.


Tom

[TinGoat]

Hi Tom,

Maybe it's not the track: Maybe it's the feeder wires.

Are you using solid or stranded wire for the track feeds?

Sometimes a loose strand will cause a short.

Or a break or kink in the feeder wires will cause an invisible short.

Wiggle the feeder wires and see if the short comes and goes...

[Sumpter250]

Hi Tom, Maybe it's not the track: Maybe it's the feeder wires. Wiggle the feeder wires and see if the short comes and goes...

If there's one chance in infinity......it is possible , maybe not too probable, but ----- I have seen stranger things than that.

( it's the -- jiggle the upstairs toilet handle, to get the furnace to come on concept )

[FiatFan]

Great ideas so far, everyone. Unfortunately the problem did not go away when I disconnected the feeder wires. After many suggestions form this and other forums, I have come to the conclusion that the problem stems from the fact that one of my brothers was born in Roswell, NM.

Seriously, thanks to everyone who has contributed suggestions.

Tom

[TinGoat]

Hi Tom,

Can't work in the sun due to prescription drugs I am taking.

Tom

I think that I may have identified your problem. You are stumbling around in the dark while on drugs.

Sorry, I couldn't resist...

From your description, I am assuming that this is an outdoor G-Scale track?

Try dragging a large magnet around the tracks. You may find an old nail or piece of rusty wire hidden somewhere. Or the ballast itself may contain some metal.

Maybe it's time to switch to battery power...

[FiatFan]

I appreciated the humor. On another forum where I'm also looking for solutions earthworms, aliens, and evil squirrels have all been mentioned as possible culprits.

That's a good idea on the magnet. I'll give that a try.

Tom

[poliss]

Could it be dissolved salts from rain making the ballast conductive?

[FiatFan]

I guess I fixed it. I went out this afternoon armed with meters, plastic bags (to put under the track to isolate it from the ground), and a determination to find the problem. Put the meter on the track and all showed good. Got the train out and it ran like a champ. Go figure.

At this point the only solution I can think of is that there is dirt somewhere that has dried enough to eliminate the short. I may soak the track good with the hose and see if the problem reoccurs.

Thanks to everyone who contributed ideas, suggestions, questions, or silliness (I've had some of that in some of the forums). Your contributions are all greatly appreciated.


Tom (still scratching his head)

[ezdays]

I guess I fixed it. I went out this afternoon armed with meters, plastic bags (to put under the track to isolate it from the ground), and a determination to find the problem. Put the meter on the track and all showed good. Got the train out and it ran like a champ. Go figure.

At this point the only solution I can think of is that there is dirt somewhere that has dried enough to eliminate the short. I may soak the track good with the hose and see if the problem reoccurs.

Thanks to everyone who contributed ideas, suggestions, questions, or silliness (I've had some of that in some of the forums). Your contributions are all greatly appreciated.


Tom (still scratching his head)

Just to save you a bit of time, but dried dirt will not be more conductive than it would be if wet. Wet dirt is more likely to cause a high resistance short than a direct one. Some "dirt" can be magnetic like if it had a hight content of iron oxide, but it still would not cause a low resistant short across your tracks. Remember though, the earth is used universally as electrical ground reference and that could possibly cause some problems depending on where your tracks are.

[FiatFan]

Thanks, Don.

Still not sure what to do next but it was definitely nice sitting on the patio with my wife an a neighbor, enjoying some patio juice, and watching the train run.

Tom