Corwin, My interpretation of the runaway direction is that it is always physically the same even when the wires are swopped to the Rx. It would be my expectation that the motor draws more current in that direction and the Rx cannot cope. It may be possible to tape on a copper or aluminium plate to the Rx to act as a heat sink. It would need to be in contact with the pair of black chips with 8 leads each and not create any short circuits. Alternatively, if this diagnosis is correct, then use an Rx with higher capability such as Rx65. I would measure current first in both directions before deciding.
The Rx led flashes once every 2s or so while searching for a signal. This pattern is easy to see every time you switch the Rx on and the Tx is off. The flashing you describe upon runaway sounds like this. When current is high, battery voltage can go low. I'm guessing the voltage falls so low the Rx switches off and reboots hence the 2s scan flashing for a while.
The Tx modules are reliable but 'forgetfullness' problems do occur. I can reinstall its software or the module can be replaced. You need to isolate problems to find faults. So if the Rx led flashes every 2s and then comes on solid soon after the Tx is switched on, and then starts flashing again when the Tx is switched off, and this is repeatable, then both Rx and Tx are probably working fine from a 'radio' perspective. The led on my receivers is intentionally fairly revealing about what it is doing once you learn to recognise how it behaves. Regards, David.
I can confirm what DavidT says about high current draw making the voltage sag. I was testing battery endurance and had fitted a audible low voltage alarm in the loco. It was disturbing hearing that alarm sounding several times on my 36 foot circuit. A bigger battery solved the problem because it suffers less voltage sag?
Hello, firstly thank you all for your help with this. I tried binding the Rx to a different setting on the Selecta, but this wouldn't work and I got only the double flash.
Then I tried the Rx on a 12v motor - no running away! Perhaps this is the issue, that the 3v motor draws too much current as you suggested?
I have some 6v motors on order which may split the difference, definitely something to try.
So far I haven't had to re-bind the Rx and Tx but I'll try leaving it for a while and test again later.