Erratic Headlight

[Frisco Larry]

I have a Kato E8/9 ABBA set. The A unit which is normally in the rear and running with the normal direction in reverse does something that I do not understand.  When the set is running forward, the rear A unit headlight should be off and generally it is, but the headlight blinks on for a fraction of a second, every 6-8 seconds. I had a spare decoder and replaced the "blinker" and the new one also blinks, at a slightly different rate.  Both decoders are TCS-K0D8-A's. The A unit normally in the front does not blink when running the set in the other direction and I have several other AA or ABA sets of E or F units, which do not do this.  It seems odd that two decoders would have the same "flaw", but I can not imagine how the specific loco could be doing this.  Does anyone have any idea what is going on and how to fix this?

[JSL]

I have had it happen on a set of F3 that were not DCC and my FVM Hiawatha loco which is also non dcc. Very strange, but could not figure out a reason for it happening.

[trainforfun]

Does it have to do with BEMF ? I think I have the same issue with a couple of units .

[kornellred]

Light sources that are powered from digital decoders should not be affected by BEMF or spurious energy spikes caused by the abrupt collapse of the magnetic field of a DC motor due to sudden loss of power, because the leads are isolated.  Since the energy pulse to the LED's is periodic, something must be triggering the output inadvertently.
It could have something to do with the "consisting" set-up.  When I run units back to back in DCC mode, I assign the same address to both units and change the normal direction using the appropriate CV (don't remember which offhand) on the trailing unit.  If that's not the way you do it, you could try this method and see if anything changes.  It is the periodic nature of the flashing you see that makes me think the decoders are not defective.
This is nothing more than a guess - I could be way off base.