Need help with a balky MPC two-position E-unit Alco

Swap motor brush leads and if it runs in reverse then it is the e-unit.  Check the finger contacts.  If it doesn't run, then it is probably mechanical in nature.  Is there some free play with the armature moving up and down.  If not loosen the set screw a turn.  G

Thank you, C.W. I never thought about that when I have a problem with one of these. You are, as the British like to say, "The Goods!" I wish I knew what you forgot about postwar trains. Thanks again.

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I wish I knew what you forgot about postwar trains.

Me too.

That is a good point.  Because of the double field in these 2 position units.  G

Was going to start a new thread, but figured I’d piggyback here since I have an MPC-era E-unit question also.

I’ve got an MPC era GP-9 (M&StL livery) that I think needs a new E-unit. Does anyone know the correct part number for these particular units?  It’s a 3-position unit with the control lever pointed down.  I may attempt the DIY route and try to clean it, etc.,  but if that doesn’t work I’d like to just get a replacement.  I did try to do a search for this info but came up more confused.    I figure I’ve got a better shot with the experts here.  Thanks in advance.

It is the same as the post war GP's, F3's, Budds, Not sure of the part number but any three position with the long handle pointing down will work...

Marty

Thank you, Marty. I think I narrowed it down based on looking at the E-units that are listed on Ebay. Not sure if I'll buy one from one of those sellers, but the descriptions helped me figure out which unit is applicable for the GP.

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I may attempt the DIY route and try to clean it, etc.,  but if that doesn’t work I’d like to just get a replacement.

With a little practice, rebuilding e-units becomes a relatively easy job. You didn't describe the problem, but there is a good chance it just needs cleaning. Most of the e-units I see on Ebay are either rebuilt units, or as-is units that probably will need a cleaning anyway.

If your problem is just a little dirt, you may not even need to pop it apart.

I would recommend unsoldering the wires and removing the e-unit so you can get to it easily.

A good portion of the e-unit drum is exposed on the side where the pawl shows. Moisten (not sopping wet) a q-tip with either contact cleaner or mineral spirits. Then rub the moistened qtip against the exposed drum surfaces. Use a small, flat screwdriver blade to turn the drum. (It might be helpful to lift the pawl away. I often slip a piece of wire under the pawl and bend it over the e-unit frame to hold it out of the way)

Continue until the whole drum, on both sides of the teeth have been cleaned.

If you continue cleaning and rotating the drum, the contact fingers usually get cleaned too.

If you are careful, a small fiberglass burnising tool can be used to polish the metal contacts on the drum too.

During this whole process, avoid any contact with the fingers. You do not want to bend them at all.

If any are bent, the e-unit has to be disassembled to correct the problem.

C.W.,

Thanks for the detailed procedures on cleaning an E-Unit. Very helpful.    I will give this a try.

I highly recommend that anybody who plans to disassemble an e-unit gets an ST-303 e-unit spreader. Reproductions only cost about $3.50.

One end has a cam that pops the frame apart without having pieces fly all over the place.

Here's a youtube video that shows how to rebuild a e-unit. Its in two parts.

http://www.youtube.com/watch?v=C3cHF_a6CNM

franktrain