MTH engine stalls on switches and isolation track

Switch the 3-rail/2-rail switch back and forth a couple times and then leave it in 3-Rail.  Measure continuity between the left and right wheels and make sure it's connected them properly.  This switch is a common trouble spot.

@gunrunnerjohn posted:

Switch the 3-rail/2-rail switch back and forth a couple times and then leave it in 3-Rail.  Measure continuity between the left and right wheels and make sure it's connected them properly.  This switch is a common trouble spot.

You know John I have one such 2 rail/ 3 rail loco and have not had any troubles but it occurs to me now that you mention it that in a derailment on a turnout a dead short through that switch might be possible. Next time I have to service it I may trace some wiring.     PTC fuse ?                             j

It is always a possibility the engine is losing the common. We had some MTH Proto 2 FT units which would stop at a crossing followed by a straight with an insulated rail. Tested using a jumper wire from the insulated rail to the other outer rail and it would go through fine. That it occurs in one direction seems to rule out the pickup spacing.

I've removed that functionality from a number of engines for customers, primarily because of the poor reliability of the two switches.  They're using ten cent switches to switch track power, and they don't always stand up to the challenge.

I did flip the 3r/2r switch back and forth, it worked a little better but only for a very short period. That leads me to believe the switch is the culprit, as you suggested.  I did not get conductivity between the drive wheels with the 3r/2r switch in either position.  I have not pulled the shell off the tender to look at the switch. I think it may be more like a 5 cent switch. Is the 3r/2r switch a SP/ST or DT or DP/ST or DT? There are some very good relatively inexpensive toggle microswitches out there that could be installed in a different location in the tender.  Since I'm only using 3 rail, bypassing the switch altogether may be a best  option.  If I understand correctly, only the 3r/2r switch needs to be bypassed?   That should be a good and reversible fix for 3r operation.  

I also placed a temporary jumper between the tenders common copper brush hold down screw and a screw on that truck near the brush. Photos attached.

I then get great conductivity between both sides of the drive wheels on the locomotive with the jumper. There is a spot on the tender common pickup truck to route a short stiff copper wire between the brush mounting screw to a truck mount screw where there will be no wire movement caused by truck rotation.  Do you think that should effectively bypass the 3r/2r switch?   Do you foresee any problems with making that more permanent, as long as the "jumper" is mechanically protected (i.e.  tacked to fixed points on the truck so it won't catch on objects?  Very small ring eyelets with the jump wire soldered to the eyelets should make good connections and not protrude beyond the brush mounting screw.  My rough mockup shows an 18ga magnet wire in a rough position just to get the idea across.  I don't know how reliable the connection between the tender truck and chassis would be.  It would take more creativity to do the same for the locomotive common brush, since that truck appears to plastic.

Another possible solution to throw out:

Will a standard 3rail, non isolated MTH freight truck wheel/axle set fit in the tender and locomotive trucks?  If so, that should help insure good connectivity as they pass over isolation track sections and switches.  If that can also work, I just have to find some sacrificial wheelsets.

Where it happens is when the non-insulated wheels on the locomotive and the tender end up on isolated rails at the same time. Basically, MTH steam 3-rail/2-rail locomotives are set up similar to a 2-rail locomotive with the drivers on one side of the locomotive insulated and the wheels on the other side of the tender insulated. The switch is supposed to connect the insulated side to the other side and fails.

We had insulated sections for signal control and this issue showed up on turnouts or when we switched the insulated running rail to the other side on curves (you want the common on the outside of a curve for better contact). The way we fixed it was to make sure that on turnouts both running rails were tied to common and that there was an overlap with switching rails that carried the common on both sides for a short distance in curve transition.

This doesn't seem to be a problem with diesel locomotives.

Matt,  I see what you are saying. I'm trying to avoid pulling switches and approach tracks to rewire & really don't want to add surface wiring -   25+ switches with roadbed & landscaping is not a very pleasant thought to run one locomotive. I have numerous locomotives that work flawlessly on the layout, but really don't want to loose this one, it's a real good looker. Now only to get it to work pulling a GGD articulated consist. Those are some nice coaches.

I think Johns suggestion to circumvent the 3/2 rail switch in the tender is a winner. 

I this happen on my two MTH diesels, so I switched which rail was the isolated rail and now they work just fine.

Thanks -  My diesels run through them just fine.  I have very solid common connection on the outside rail of each switch and switch exits. One side of the loco is not picking up the common, apparently a poor designed & or bad 3R/2R switch in the tender.. I can't find a quality replacement switch that fits in the original location so it's bypass time.   I think I have an even simpler solution that will work well, just waiting for a couple grounding tabs before I can try it.  Could make some, but I found some ground tabs that should be a perfect fit. I can't get any electronic supplies locally anymore, the last shop in the area closed a few months ago - have to order almost everything, including any through board part like resistors/ capacitors/ regulators etc, or a 2+ hr round trip, at least in my region.

I have just one 3r/2r convertible steam loco that's making me loco. All others work fine. My isolation rails are all fed from underneath and are a bit difficult to access without pulling up ballast/ landscape, etc. All are soldered power and isolation rail connections for extreme contact reliability, no lock ons.  I'm trying for a solution to not have to rewire. Rewiring 25+ switches (50 isolation rails)  w/ trackbed, ballast/landscape to run one locomotive is just not very appealing. Call me lazy I guess.

@BrettH posted:

Thanks -  My diesels run through them just fine.  I have very solid common connection on the outside rail of each switch and switch exits. One side of the loco is not picking up the common, apparently a poor designed & or bad 3R/2R switch in the tender.. I can't find a quality replacement switch that fits in the original location so it's bypass time.   I think I have an even simpler solution that will work well, just waiting for a couple grounding tabs before I can try it.  Could make some, but I found some ground tabs that should be a perfect fit. I can't get any electronic supplies locally anymore, the last shop in the area closed a few months ago - have to order almost everything, including any through board part like resistors/ capacitors/ regulators etc, or a 2+ hr round trip, at least in my region.

I have just one 3r/2r convertible steam loco that's making me loco. All others work fine. My isolation rails are all fed from underneath and are a bit difficult to access without pulling up ballast/ landscape, etc. All are soldered power and isolation rail connections for extreme contact reliability, no lock ons.  I'm trying for a solution to not have to rewire. Rewiring 25+ switches (50 isolation rails)  w/ trackbed, ballast/landscape to run one locomotive is just not very appealing. Call me lazy I guess.

Again, bad switch or not, that engine is losing the common connection. As mentioned you'll either have to replace or bypass the engine switch or modify your track wiring. (Or just run it the direction where it doesn't stop:-) keep us updated on your solution.

All wheel sets are not switched when going to 3 rail on premier steam.  Only a few are.  In extreme cases, you can remove the plastic bushing on the isolated sets and replace them with metal ones.

IMO, the 2-rail/3-rail arrangement for the MTH convertible locomotives is a bit of a kludge.  I get lots of repairs in that are related to that cheap switching arrangement.    On PS/2 stuff with the polarity switch as well, I've had a number of people just have me remove both switches and hard-wire them to 3-rail operation.

Dave is, or course, right about the switching.  you lose some continuity to the wheels with the 2-rail/3-rail kludge as well.

John,

After loosing more hair than I have to loose,  I came up with a real easy fix for the GS4 that stalls on switches and isolation rails.  Now the GS4 will crawl though all the switches on my layout.  Whew.  Your note about the poor quality 3r/2r got me thinking about the common for a 3 rail setup.

Simply reverse one wheelset on the front truck of the tender, and reverse one wheelset on the trailing truck on the GS4 locomotive. That allows very good conductivity between all the drive wheels, with a resistance of about 2 ohms between any opposing wheelset.   It's a backwoods way of bypassing the 3r/2r switch.

I marked the wheelsets that are reversed, and made a note to realign them to the stock orientation if it is ever to be used as a 2 rail.

Thank you so much for helping get this problem resolved.   No track / switch rip-outs / rewiring needed as many suggested.  The GS4 still gets a signal of 10/10 around the track with the quasi inverted pickup wheel setup. (~450ft of track - not a huge layout)

Now to figure out how to get the pilot wheels to trigger the Z1000 switches.  Switches wont trigger until the primary drive wheels hit the isolation track. It doesn't look like they disassemble easily to do invert one of the pilot wheelset.

Whew.

Maybe you can find a pilot that works that is not 2-rail compatible?

I don’t know if this’ll help or not, but on some of my “ normal 3 rail “ engines, a buddy of mine showed me a trick to run a jumper wire from the pilot truck back to the commons....helps a lot with some stubborn offenders,.....in your case, you’d still need to flip the pilot wheels around to get the best connection,...I just looked through my junk, I’m clean out of scale pilot wheels,...or I would have offered them up,...sorry,...I just drilled and tapped the top of the pilot truck itself for a 4-40 screw, and used a small wire eye and routed the wire up into the frame,....

Pat

Dave and all,

Replacing the insulating plastic bushing with metal bushing would could be a great help also, for 3 rail only. Any idea of the part number/ sources for replacement metal bushings? I'm coming up empty.

Thanks all for your input.     I'll work on getting the pilot changed to a conventional 3 rail, by either flipping axle orientation, finding a donor 3 rail pilot or adding a chassis wire.  All good suggestions