Bachmann class 40 ( and others) circuit board mods,

[nimbamoss]

I have finally plucked up courage and done the circuit board mod. This places the control of the tail lights on Aux 1+2, while the Cab lights are on Aux 3+4.  I have removed the control switches in the tanks to fit a High Bass speaker.

All seams okay, the outputs have been rehashed to be 21,22,23 and 24.
All tests OK with an led on the terminals for cab lights and rear lights but when the body is fitted I keep getting a problem.
When the headcode lights are of and the cab lights turned on the headcode light comes on and when this is repeated with the headcode turned on the headcode lights brighten when the cab light is operated.

Any suggestions?

I was thinking a back feed or not enough resistance (I have used a 2k2 SMD).

Many thank for your help in advance

 

 

Ian