Another Sticky E-Unit Question

With 1.5 volts and a load on the track, I would say it's a transformer issue.

From what you have said, other locomotives are working correctly, which would localize your problem to this locomotive.  If you are using a PW transformer, some voltage bleed while it is set to zero is not uncommon and not a problem.

If you removed any wires during cleaning and lubrication, check them to be sure you put them back correctly.  Check all of the fingers to be sure they are contacting the drum properly.

The transformer is a postwar ZW.  I've not taken the e-unit apart, only cleaned the drum with a Q-tip and alcohol.

Look at the fingers, there are 4 on top and 2 on the bottom.  They should be contacting the drum and not touching each other.

WD40

99% of the time I can get the e-unit to work properly with cleaning, lubrication and adjusting the angle of the pawl. The 1% of the time where nothing works, I put 1/2 of a 671-140 spring (used in the horizontal e-units) above the plunger.  Helps the pawl drop down.

Well, that issue resolved itself and is working fine now.  Moving on to a different issue.  Subject is a pre-war 1684 steamer.  I acquired it in a hot-wired state but was able to extricate the Frankenstein-like appendages a previous owner installed (really, it made no sense).  I've cleaned it up, installed a new drum and fingers, and put it back together.  The e-unit cycles fine, but the engine won't turn.  I tried a different e-unit but the result is the same.

I've noticed two different kinds of e-unit-to-motor connections in pre-war units - one where the blue and yellow wires each connect to a brush and the green connects to the motor winding, and one where only the blue wire connects to a brush and both the green and the yellow wires connect to the winding.  Does anyone know why they are different?

Anyone have any thoughts on the solution?

Here's my thoughts, FWIW, YMMV. A postwar engine e-unit sends power out to one brush, then back to the e-unit through the other brush wire and then back out from the e-unit to the field winding where it goes to ground after going through the field coil. The coil only has 1 lead ( the coil winding wire is soldered directly to the frame in most cases) on these engines.

IIRC, on some prewar engines ( and including postwar 1656) the coil has two wires and is insulated from the frame. Power comes from the e-unit, goes through the field coil on one wire, then back to the e-unit on the other field coil wire to be sent back to an armature brush on one wire. The other brush goes to ground. Hope this helps.  The field coil and how it's wired is the give-away to figure out how it's wired.

I don't have wiring schematics for prewar engines, but I have rewired a couple, along with a 1656, which has a schematic in the Greenberg Repair Manual.

Ed Horan