MTH Locos stuck in Lionel Accessory Activation Section

Are you using insulating track sections?  Are these premier locos with 2/3 rail capability?  If so, the MTH locos with the plastic baseplate on the power truck have problems with continuity between the wheelset and truck block, and with the 2/3 rail switch.  Check continuity between wheels on opposite sides and opposite trucks.  If the former, 0.005” shims are installed between the bronze bearing and truck block.

Railking diesels had some problems (rare, but I seen a few) where the coating on the truck block interfered with the ground path through the axle bearing.  Continuity checks will confirm this.

Hi Jon,

Yes, they are Premier locos with 2/3 switch. . I have 3 Dash-8s and they don't do it. Yes, its a Fastrack insulated section. I'll have to take a night and check the continuity. May be later this week. I'm just trying to get my head around it. These are all new locos within the past year, but just out of warrantee (of course!) . I don't think the problem showed up until I installed the insulate track sections a few weeks ago.  

We noticed this problem on the test track at MTH where a route had only one outside rail grounded.  Excessive play in the bronze bearing to the truck block or a bad 2/3 rail switch.  Shimming corrected it 99% of the time. K&S sells some shim stock that works. Others have found material in Hobby Lobby.  Cut and shaped into a “U” to cradle the bearing eliminates the play.

Remove the pickups and the 3 or 4 small black screws, lift off the plastic baseplate to access the wheel sets. Easy-peasy.

@Jon G posted:

We noticed this problem on the test track at MTH where a route had only one outside rail grounded.  Excessive play in the bronze bearing to the truck block or a bad 2/3 rail switch.  Shimming corrected it 99% of the time. K&S sells some shim stock that works. Others have found material in Hobby Lobby.  Cut and shaped into a “U” to cradle the bearing eliminates the play.

Remove the pickups and the 3 or 4 small black screws, lift off the plastic baseplate to access the wheel sets. Easy-peasy.

Sounds great. Images?

@BobbyD posted:

Sounds great. Images?

Note that the shim goes on the bearing side, not on the insulated bearing.  Do all three (or two) bearings.

For the 3/2 Rail Switch, I have removed them for a number of customers.  Those are one of the prime problem spots for the switchable engines.

That doesn't sound too difficult, but what do you do with the leads if you remove the switch?

I took this 6 month old GP-40 apart to establish a baseline. I haven't meddled with anything, but wanted to document the wheel arrangement before I took my others apart. Should I have continuity left to right and front to back amongst all the outer wheels??

Or should I go straight to the 2/3 switch?

I did shunt the insulated track section with a jumper and the loco ran right across it, so I'm thinking something is up with the outer wheel

Thanks Guys!

The wheelset axles are split and insulated in the center.  You should have close to zero resistance from side to side and truck to truck, but the plastic baseplate has to be in place as it has the jumpers to pick up ground from the insulated bearings.  If resistance is high (not infinite), my guess would be to shim the bronze bearings first.  If resistance is infinite or very high, check the switch.  When assembled, if the switch is clamped crooked, it mashes the contacts so they don’t make good internal connection.  The black wire connects to the truck block which picks up ground from the bronze bearings, the brown wire picks up ground from the insulated bearings, the red wire is the center pickup.  Connect to brown and black wires together to tie both sides of the wheel sets together if you want to bypass the switch.

Jon,

Taking advantage of the dank New England weather, I finally tackled the 2/3 wire dilemma. Following you recipe, I eliminated the 2/3 switch sucessfully on my first patient. I went straight for the switch over the wheels, have viewed it as a "final cure".

I took the second GP-40 apart, expecting to do the same, but much to my chagrin, dicovered melted wires. See attached pics. It seems to be only these 2 wires, one red and one black, that are affected. Any idea what would have caused that?? I'm thinking it was stalled out across across a with or something like that....or under voltage??

Happy New Year, and Thanks!!

Bob

Goodness, something bad happened, that's for sure!  If it's running, I'd carefully replace the wires during the switch removal.

Yeah, pretty nasty looking! That will be tomorrow's rainy day job. Thanks for the reply!