Madman said:
Yes, I measured the voltage and it starts out at lets say 12 volts at the track, then goes to 0 volts after a second or two.
Just to make sure that your power pack is fine. Could you test the line with the reverse unit out of the equation and feed from just the powerpack. I am not sure what power system you are using but the voltage to zero effect occurred on a failing Train Engineer receiver of mine. It is probably not your pack but it is best to eliminate it from the possible problem.
If the line and power is fine with no possible shorts etc. Then the last thing that could be wrong before blaming the shuttle unit as the culprit is a dodgy diode (although this should not really create an effect like you have). Once the power pack has been tested and is fine, test the line diodes by putting the multimeter set to OHMS before and after the diode. with the probes one way there should be total resistance, the other way should show a measurable resistance (on my meter it is about 490 to about 600 ohms on all my shuttle diodes). Then test them with voltage applied to the track. Before and after the diode - depending on the way around the probes are applied you should get full voltage one way and none the other!
Another even better way to test is by using an actual loco on the track - still without the reverse unit and power straight from the tranny (or receiver in my case) put the loco in the middle of the shuttle line, apply power and it will go to the end of the line (if it does not move, reverse the polarity of the track) when it gets to the end of the line it will stop once it has crossed the diode gap. Reverse the polarity to the track and it should start back down the line and do exactly the same at the other end where you again reverse the polarity to the track and it should go off again. If this happens then the diodes are perfectly fine.
Re attach your reversing unit. Try the same loco. If it does not move , reverse the polarity of the power pack to the reversing unit. If it does not move or bunny hops then it does look like the unit is up the creek.
I hope this helps.
My 5 ampo reverse unit seemed to be playing up (a loco was going through the diode and carrying on!) but under test all diodes are fine, weith another loco the unit was fine so the culprit was the loco. I had been added a sound board to the loco and had not been careful enough and the wiring which had somehow caused the loco to waft through the diode gap.:wits: