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Discussion Starter #1
Hello,
I have two Lionel 8403 (4-2-4) units that I've been given and am trying to get running properly for the holidays. Both units have the same problem. They will go forward, but not reverse. When the e-unit is engaged the unit will cycle F-N-N-N-F. They have the PCB e-units which I suspect is the problem. However, after doing some reading on some forums, including this one, and I have gotten different solutions. Some say it's best to replace the motor along with the e-unit and some say to replace the whole motor assembly with the older mechanical e-unit.
I did do some testing on the motors with a 9v battery connected directly to the motor. In this case, both motors will run forward and reverse when I switch polarity. I am also using post-war transformers. I don't know if that causes problems with the PCB e-units.
I am relatively new to this and appreciate the help.
 

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Welcome to the forum!

As you suspect, the electronic 'E' unit boards are faulty.
The motors check OK, so they don't need to be replaced now, but the brushes on them wear out after time and then they will need replacement.
Replace the boards, as they are known to fail and you will be back in business. Replace the motors also to be safe.

Larry
 

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Welcome to the forum!

As you suspect, the electronic 'E' unit boards are faulty.

Larry
I concur. The OP's list of the direction sequence "F-N-N-N-F" would suggest that the board's reverse drive electronics have failed: the power transistors or their electronic triggers.
 

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Larry is right, those transistors are frequently toasted by the crappy motors they used, so it's normal to follow Larry's advice and replace the motor with the reverse board. Truthfully, I'd probably consider a spike suppression capacitor at least across the motor leads.
 

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Discussion Starter #5
Thanks for the advice! I’ll have to look into those capacitors. They sound like a good preventative measure.
 

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Discussion Starter #6
Finally got to installing the new motor and e-unit and it works great - mostly. I modified the connection to the smoke unit such that I could turn the smoke part on and off. The way I did it there are two hot wires going to the smoke unit. One is for the light on the unit and the other is for the heating coil which runs through a switch. I used a common ground. The problem is that when I run the train with the heating coil on no matter what I set the throttle to the train doesn't accelerate, but there's plenty of smoke. The train runs so slow it's almost stalling. Any ideas? I've attached a diagram of my wiring, modifications in red.
Lionel eeunit wiring diagram copy.JPG
 
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