Neded Help With a Lionel ElectroCoupler PROBLEM RESOLVED

First, ensure you are giving the engine a full 18V AC on the track.

The fact you hear the buzz, the board is working correctly- this is purely that coupler and the voltage required to pull the plunger back to unlatch the knuckle.

It's possible your coupler and it's internal spring and details just require higher track voltage or gentle working to remove any burrs preventing the plunger from pulling in an releasing.

You might try a straightened paper clip wire or similar to push inside the knuckle area to hit that plunger and depress it a few times to loosen it up.

Go the support page for the engine https://www.lionelsupport.com/...-Unit-9501-B-6-24563

From there, you will notice this uses the R2LC TMCC modular control board style system and that is what fires the coupler. If you hear the buzz, that board is working- period.

If you still cannot get it to physically unlatch, then there may be a defect in the coupler https://www.lionelsupport.com/...-LENGTH-1.74-2-LEADS

@jpnrc,

Vernon's right on track.

Here's more detail in case you need it.  Two things to check.  Both of them are measurements and are easiest with a Volt-Ohmmeter of you have access to one.  Here's what you need to find first before measuring, the motherboard:

Here's what you need to measure:

1. Coil Coupler Resistance -- Unplug the plug that is presently plugged into the above connector.  Measure resistance between the two adjacent pins, on the harness end that you just unplugged, that correspond to the pins circled in yellow above on the motherboard.  You should read low ohms, if I remember correctly about 4.  It shouldn't be any higher than maybe 16.  If it is then the coupler is bad.
2. Coil Voltage -- Reinsert the plug that you unplugged.  Try it again.  This action in itself might restore operation.  If it doesn't measure the voltage between the same two pins, from the backside of the harness connector with it plugged in.  You should read 18 VAC when you push the uncouple button, and hear the faint noise, and 0 when not pushing the button.  If you don't get 18 VAC with the button pushed you probably have a bad R2LC board. which is the board plugged into the motherboard that engages with the right-angle brass pins in the picture above..

Good luck.

Mike

My experience with many couplers is they need at least 15-16 VAC on the tracks to function properly.  Make sure you have sufficient voltage, it's the most common issue.

Thanks Guys.  I'll give all that a shot and let you know how it turns out.  John

SUCCESS!!  Vernon was correct that the coupler was physically closed too tight.  I released it with a paper clip as he suggested, and once I got it opened it now works correctly both closing and opening again.  Thanks so much.

One important point regarding Hudson Mike's comments.  The rear coupler wires are not connected to the bracket that Mike circled on his photo.  Rather they are the connected to the bracket that plugs into the pins on the far left of the motherboard.  They are the third and fourth wires from the top of the pins in the picture (the third pin from the top is marked "rear coup").  I did test those 2 wires with an ohm meter and got 8 ohms, which was within Mike's 4 to 16 ohm range.  So at that point since the coupler read good and I was was hearing a buzz, I took Vernon's suggestion to see it was physically stuck and found that it was.

Thanks again for the speedy and helpful responses.  John

I've found that sticking couplers aren't necessarily "closed to tight", but rather have flash or other deformities that stick them shut.  Don't be surprised if the issue returns.

@jpnrc posted:

One important point regarding Hudson Mike's comments.  The rear coupler wires are not connected to the bracket that Mike circled on his photo.  Rather they are the connected to the bracket that plugs into the pins on the far left of the motherboard.  They are the third and fourth wires from the top of the pins in the picture (the third pin from the top is marked "rear coup").  I did test those 2 wires with an ohm meter and got 8 ohms, which was within Mike's 4 to 16 ohm range.  So at that point since the coupler read good and I was was hearing a buzz, I took Vernon's suggestion to see it was physically stuck and found that it was.

Ok.  Excellent catch.  Sorry about that, but unlike some models I didn't have one of these to disassemble for confirmation.

So the set of pins I had previously circled are apparently used for a front coupler, if your unit has one, and yours doesn't because it's a 'B' unit.

The pins you mentioned, at the the other end of the board, are indeed for the rear coupler, and if you look closely at the photo they seem to be labeled as such, although in tiny and slightly blurred lettering:

Glad you figured it out.

Nice to know what was really the problem.  It will help other folks in the future.

Mike

Thanks for the heads-up GRJ.

Mike, you're exactly right about the B unit only having a rear operating coupler.  And I agree and hope that that this info, especially with your photos added, could help others in the future.  Having been through it, I would suggest trying to free/open the coupler using Vernon's method and then test it on the track.  If that works you avoid having to dig out the meter, remove the shell, start pulling plugs, etc. Wasn't a problem for me b/c mine was already opened.

Good luck all.  John