Updated 06.04.2013

This train set will run behind Märklin 3103 T 12 7896

Märklin 4035

A black wire runs through the train, from the luggage car to the green front car, partly visible in the photos.
Behind the locomotive: 1235, next 1418, then 1604, finally luggage car 3103.

Function decoder:
A Märklin 60960 function decoder and a relay is installed in the luggage car 3103 Pi.

The pick-up shoe:

This type of car has a pre-cut part of the floor, meant for installation of interior light kit 7323.
But, I did not want to make a "big hole" in the floor, so I just drilled a small hole and installed a pick-up shoe meant for Märklin 4103 and 4316, luggage car Pwi 30.
A small drop of glue fixed the pick-up shoe perfectly.

3103 Pi inside:

I made a small dividing wall between the conductor's department and the luggage area.

A little bit of interior:

I do not know if this car ever had interior, so this is free imagination

One of the train crew is having a well deserved rest:

The luggage car has a single rear red light:

I do not know if these cars ever ran with such a rear red light, but I have seen something similar in some old photos.

The rear red light connection from inside:

Light in the other cars:

I made three metal bars and installed them in the three passenger cars.  I drilled small holes in the front left and rear right seat and glued the metal bars under the seats.
One leg from the two 600080 bulbs are soldered to the metal bar.  A black wire, current from the baggage car, is soldered to the free leg of the rear bulb. The black wire continues to the front of the car, to connect to the next car.  The free leg of the front bulb is connected to the car chassis, at the leaf spring for the coupler.  The leaf spring has good contact with the metal part under the interior and with the wheels.

The couplers between the cars:

The couplers at the consist ends:

The decoder in the car is set to the same address as in the 3103 locomotive, so I can control it all under the locomotive control.  See the left part of the below screenshot.
The right part of the screen shows the control car of the coach set by itself, but will seldom be used.

The decoder functions:

function		Locomotive 3103	Car set 4035
f0	f	3 front lights	-
	r	2 rear lights	-
f1		-	interior light in the connected three coaches, via a relay
f2		-	interior light in conductor's cabin and one rear red light
f3		-	interior light in the luggage area
f4		acc/brake delay off	red LED inside the luggage area, just for fun

Screenshot from my Central Station 1:

The left part is 4035 in consist with locomotive 3103.  The right part is 4035 only, and will not be used that much.

Parts used for the installation:

Part No.	Description	Pcs.	Remarks
60960	Function decoder	1
456200	Holder for decoder	1
310510	Pick-up shoe	1	For 4103 and 4316
600080	Bulb	6	Interior light in coaches
-	28V T1 bulb	2	Interior light in baggage car
-	Miniatyre relay	1	For f1 interior light
-	1,2 Kohm resistor	2	For LEDs
-	Red mini LED	1	Rear red light
-	Red 5mm LED	1	Interior light for fun
-	1-pole connectors	6	Cut from a 20 pole SIL connector

The wiring diagram for 4035:

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