Hi, just picked up a nice 3611 steam loco. But it’s acting weird: it’s only going forwards! The lights reverse properly but the motor only seems to want to go one way. Any idea on what could be wrong?

Hi Kaspar
I have the very same loco with a "Glockenanker" Bell-shaped armature. Runs smoothly and silently
So your motor turns only in one direction and here are the possibilities
- the motor brushes are worn in one direction and need a bit hep when reversing at start
- to be sure the motor is not faulty, disconnect it and apply a DC voltage (5 V to 10 V, possibly using a 9 V battery. Check both directions
- no wire could be involved otherwise the motor won't run at all.
- one of the driving transistors in the decoder is fried (there are 4 of them in a H arrangement to control the speed and direction



If none of the above is working then a change of decoder is needed. Why not have a mSD3 BUT:
- you need to change the ski as the original one has a long bar clipsing directly into the decoder
- you need to check where the resistors of the LED headlights are located
- NEVER EVER unplug or plug the LEDs while the loco is power ON at it will SURELY destroy them.

Cheers
Jean

I didn't convert my 3511 myself.I suspect that only difference from a 3611 is the 5 Star motor regulation and the two potentiometers for acceleration delay and maximum speed. It's a gut job to upgrade. Mine was converted before the sound decoders were available, so it's a 60901. If I were doing one today, I would use an msds or MFX wired type.I don't think the tender has room for a plugin PCB board. Even the old decoder is a tight fit with all the wires.

Good advice all around. I also used a Luessi board in my 3611 and an ESU decoder after the original decoder failed.

Modern electronics and that beautiful motor are a great combination and a nice upgrade to a steam era icon.

First off, thank you all for great responses, this forum is such a valuable resource for Märklinists.

To answer your question Mike, the engine operates as expected in forward. In reverse it switches lights but still runs forward. So basically it always moves forward. From the information given here I’m guessing the decoder is not reversing the voltage sent to the motor, will try to test the output voltage.