On some of those old engines there was a lever on top that could be flipped to one side to lock the reversing relay in either forward or reverse. Barring that, I would not tinker with the internal wiring unless you know exactly what you are up to.
I suspect this is an O/O-27 tinplate loco - you might have better luck in the Classic Toy Trains forum, surely there are people there who collect and repair Marx equipment and could provide you with detailed guidance. Not that there aren;t people here who couldn;t figure it out - but I don';t happen to have any Marx locos to look at, or instructions or books about them.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
trainsartistHi. I'm brand new here and I have a rather simple request for you experts. I've got an old model marx engine that shifts into reverse when power is shut off then applied again. I want the engine to always go forward. Is there a way to modify the wiring to stop any reverse function? Thanks for the help. Jeff
I assume you do not realize that this is a deliberate part of the locomotive's design. "Tinplate" trains like Lionel, American Flyer, and Marx run on AC power. With AC you cannot change the direction of the motor simply by changing the polarity of the rails. As you can with DC powered trains. So with AC powered trains the engine or tender will contain a mechanism, usually refered to as an "E-unit", which reverses the motor every time the power is applied. It's clunky, but it's the only way to make it work. As was noted earlier, some locomotives have a switch on the unit that allows you to select forward-only operations, but they are the exception rather than the rule. You can take out the E-unit if you want, but only if you really and truly never want to run your locomotive in reverse again! And of course if you wire it the wrong way you'll have a locomotive that ONLY runs in reverse.
I have figured out what is wrong with my brain! On the left side nothing works right, and on the right side there is nothing left!
Most Lionels have forward-neutral-reverse-neutral-forward sequence, instead of just forward-reverese. Also, some Lionels had a small plug and socket to disable the "E-Unit" rather than the switch sticking out the top. Dunno anything about Marx.