Lionel Fastrack Uncouplers don't work properly thourgh MTH AIU

Since you say the manual pushbutton also doesn't work, it seems to eliminate the AIU as the issue, or am I missing something here?

I think part of the issue would be the #22 wire, that's pretty fine for the magnet drive.  Those suckers take quite a bit of power to operate.  I connected one to a 1033 at full voltage and got 2.4A of current draw.

I think John has the answer.

#22 wire has too much resistance to the foot for the kind of current you are running.

I had similar issues with using that type wire for my switches. Doubling up the primary power wires helped.

I tried increasing the power from the aux transformer (1033 at full track power) to 16V, and the uncouplers still did not uncouple properly. The magnet was activated enough to pull a screwdriver head to the magnet, and will uncouple some cars, but not most cars.

I then changed the power wire back to track power, using the telephone wire. The track power goes about 5 to 10 ft from the uncoupler to the AIU through the telephone wire (yellow), then goes through the AIU, then back to the magnet (green wire). Although the distance through the telepone wire is about 10 to 20 ft in total, the uncoulpler works properly now. The track voltage now supplies 18V at the AIU, rather than the 14V (which was 10V originally when using the AIU aux power connection) at the AIU using the 1033 (which read 15V at the transformer).

The Fastrack uncoupler is supposed to operate at 10-12V, according to the manual. However, at this voltage, it doesn't have enough strength to uncouple all my cars (some of which have rather stiff uncoupler pins).

I have resolved an earlier problem of the uncouplers staying in the ON position throught the AIU. I upgraded the DCS and Handhelds to V4.20, which fixed a bug that sometimes caused the AIU to "stick" in the ON position. (which is very bad for the uncoupler, as it melts and burns whatever surface the uncoupler track is sitting on). that is a $35 expense every time it happens.

I am not sure I fully understand why the 1033 doesn't work at 14V, when the uncoupler manual says the uncoupler should work at 10-12V. The wiring in both situations (using the 1033 aux power and track power) are the same. the wire from the uncoupler to AIU is 22GA phone wire.

The aux power goes from the 1033 around the room to distribution terminal strips. The terminal strips are about every 15 ft, with the longest wire run about 50-60 ft. The distribution wiring for the 1033 is 18GA wire, which I thought would be enough to carry the load without any real voltage drop.

Although my problem is solved (by using track power through the phone wire), I am not sure I should give up on using lower voltage Aux wire. I may try a test by hooking up an uncoupler test track beside the 1033, then try different wire sizes to see if I can isolate the problem as noted in the posts above.

Does anyone know of a disadvantage of simply using the 18V track power to power the uncouplers? I have been doing that manually (not using the AIU) for years.

Thanks: Joe K

My major issue with using track power for the couplers is it upsets some locomotives when I uncouple.  Of course, if you have several locomotives and perhaps lighted passenger cars on that power district, you can also push it over the edge with the 2+ amps for the uncoupler.  The higher the voltage, the more current it'll pull.