# Reverse unit problems



## AFGP9 (Apr 8, 2015)

Hello all,
Many time viewer/reader, first time member. After reading lots of problems and "how to fix it" responses this looks like an excellent forum for problem solving and advise. 
I am a long time collector of AF and am very familiar with the inner workings of the AF steam locomotives and tenders. 
The problem I have encountered involves the reverse unit in my 322 locomotive. Everything is fine with regard to the fingers, proper drum rotation and lever engagement. With power to the locomotive setting on the track and the tender body off, I can watch the drum turn and cycle like it should but nothing happens. With the locomotive isolated from the tender and power put to it, it runs fine. It just doesn't run with the two pieces together. 
Any body got any ideas? I suppose I am missing the obvious or something like that.
Thanks in advance.


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## rkenney (Aug 10, 2013)

Check your reverse unit contacts to make sure they are making a good connection. These diagrams should help:


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## longle (Mar 7, 2015)

If it works with the loco and tender uncoupled but does not work with them coupled that sounds like there is a short somewhere. Assuming the wiring is correct, my first inclination would be one of the truck rivets on the tender is shorted to the chassis. My second inclination would be one of the wires in the loco is shorted. As long as they aren't coupled there's no problem but as soon as the two are coupled there is a full fledged electrical short.

My Hudson is packed away right now but I believe that is a 4 wire unit. Here's the diagram for a 4 wire unit.

Larry


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## AmFlyer (Mar 16, 2012)

If I am correctly understanding the facts posted the drum is rotating when track power is cycled and when power is applied directly to the motor in the engine the motor runs. Assuming the fingers are making good contact with the drum then there appears to be a bad wire in the 4 wire harness or a bad solder joint on one of the harness wire connections. Check this with an Ohm meter or continuity tester. Put one meter lead on one of the 4 pins on the harness connector and touch the other end to each of the connections in the tender. One should show zero resistance. Check each of the 4 connector pints to determine if one of the wires is bad. The connections to the pickups on the tender trucks are good if the drum rotates. If you have tested the engine without the drawbar connected then it would not matter so far if one of the leads in the engine was shorted to the casting.


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## longle (Mar 7, 2015)

As I read the OP I take it that it works as long as the drawbar isn't connected between the tender and loco.


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## flyernut (Oct 31, 2010)

With the tender connected to the loco, use a toothpick to push against the fingers. I had several tenders that would not work with a loco, and after doing the toothpick thing, I found that the fingers were not touching the drum. It LOOKED like they were, but they weren't.


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## AFGP9 (Apr 8, 2015)

*Reverse unit problem*

Thanks to all for the response and suggestions. I think I need to clarify a couple of things. 
When I said that with the locomotive isolated from the tender and power was applied I meant power was applied to the locomotive not the tender. The locomotive was completely unhooked from the tender, drawbar and the wiring. I have a test harness that I can plug into the loco board and then to the base and variable posts of the transformer. That way I can check locomotives for running or not. 
As I said the loco runs fine in this configuration. The problem occurs when I put the tender and the loco together and put them on the track and power up. The reverse drum turns as it should but no movement or cycling. The lever falls solidly on each step of the drum as it rotates when I move the transformer power off and on. I will recheck my finger connections and their contact. 
I'll do the toothpick trick suggested by flyernut first then get the Ohm meter out if the toothpick trick doesn't work.


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## flyernut (Oct 31, 2010)

Just follow the path of electricity to the loco. First check the trucks,( sounds like they're ok), then the fingers, and then your harness. It sounds like the power isn't transferring to the loco from the e-unit. I'm sure the problem starts with the fingers, and goes from there. It also sounds like the jack panel is also ok as you can power the loco with your harness, eliminating the tender. I believe the problem lye's somewhere between the male plug, and the fingers. Not to insult your intelligence, but make sure when you check those fingers with the toothpick that the drum is in a "run" situation; i.e. forward or backward. Let us know how you make out. If you need a new wiring harness, I have some here. Just pay the shipping....Loren


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## AFGP9 (Apr 8, 2015)

Thanks for your input flyernut. I will check as you suggest.


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## Nuttin But Flyer (Dec 19, 2011)

In the past while doing my own servicing, I have found that some repro finger assemblies have manufactured the copper "finger" strips just slightly longer than necessary. What I found is that this extra length causes the finger to ever so slightly miss the proper spot on the drum and thus is not conducting power. To remedy, I slightly bend the fingers to provide additional arching effectively "shortening" the length so that they fall squarely on the copper spot on the drums sections. Just a suggestion to check.


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## flyernut (Oct 31, 2010)

Nuttin But Flyer said:


> In the past while doing my own servicing, I have found that some repro finger assemblies have manufactured the copper "finger" strips just slightly longer than necessary. What I found is that this extra length causes the finger to ever so slightly miss the proper spot on the drum and thus is not conducting power. To remedy, I slightly bend the fingers to provide additional arching effectively "shortening" the length so that they fall squarely on the copper spot on the drums sections. Just a suggestion to check.


I was wondering when you were going to chime in!!! I might be the resident surgeon, but you're the chief of surgery!!:smilie_daumenpos:


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## AFGP9 (Apr 8, 2015)

*Reverse uint problems*

Yes you are correct Nuttin But Flyer. I too have encountered the same issue. That was checked on my problem 322.


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## AmFlyer (Mar 16, 2012)

There are years of experience and expertise shared in these posts. In my personal experience most failures are related to the fingers. Even the toothpick trick only works 3/4 of the time because sometimes more than one finger is not in correct contact with the copper segment on the drum. A visual inspection is rarely adequate. I have worked on close to 100 AF steam engines. Cleaning, repairing/adjusting the fingers and fixing the 4 wire harness resulted in all but one engine working. That one had a broken wire in the armature. 
Tom


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## AFGP9 (Apr 8, 2015)

Thanks AmFlyer for your thoughts on my problem. I too have worked on a number of steam locomotives. I always visually inspect the drum and fingers for contact and condition, and repair/replace if needed and clean the drum as needed. When I bought this 322 all appeared to be in excellent condition. I did not check the wiring with the Ohm meter after having the problem. One of those obvious things to do which I mentally blanked out on. Maybe I need to make check list.


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## Nuttin But Flyer (Dec 19, 2011)

In your first posting, you stated the engine ran fine by itself when power applied. It's only when tried through the tender that it doesn't run. It hums, so it is getting power at the wheels/tender rivets I assume. So that has to mean either bad wiring from the reverse unit to the engine -- broken or loose wire, incorrect wiring. Or the reverse unit is not providing power as it should -- finger contacts missing drum contact surface, hole in finger end. One other thought just came to me, check to be sure the finger assemblies are oriented in their proper places -- I sometimes get this messed up myself, but I believe the offset pair goes on the top of the reverse unit and the centered set in the front. Someone here will certainly correct me if I have that reversed. Use a multi-meter set to "resistance or ohms" to check conductivity in each wire searching for broken or loose wires and solder joints. You might also try this method between the reverse drum surface and the corresponding finger contact it should be transmitting the power through. That might show a finger is missing the drum surface. A good connection will display zero resistance, a bad connection will display infinite resistance or no reaction at all. Check every solder joint and connection from the tender pickup rivets to the rear engine jackplate plug. Something has to eventually be found.


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## longle (Mar 7, 2015)

Nuttin But Flyer said:


> I believe the offset pair goes on the top of the reverse unit and the centered set in the front.


Yes, that is the correct orientation for the contacts.

Larry


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## AFGP9 (Apr 8, 2015)

Thanks for the information Nuttin But Flyer. I will try all the checks that have been suggested. I won't be able to get back to it though for a couple of days. 

Ken


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