10-Pin Connector?

No, there is at least two standards, one for diesel and one for steam.

I use them for upgrades, I just plug them together and ring them out and match the colors at each end.

No. Some of the early steam PS-2  had the board in the engine.  Most boards now are in the engine. Quite a difference in wiring features.

Nope, You have loco sound wiring, you have 5V wiring with board in engine, board in tender, battery in engine, battery in tender, so you need to be careful.  For PS-2 3V you have MUX board and non Mux board engine.   All ten pin external harness are straight thru design, but diesel and steam are different in what gauge wire is at what location.

Similar differences in 5V versus 3V ABA Slave harness.   G

I always make sure I use the four heavy wires for power and motors.  For smoke, I usually double up two of the fine wires as I typically have spares for TMCC upgrades.

Not sure by the answers that I asked the right question.

PS2 Steam engines...is the plug wiring on the rear of the boiler "standard"?

I have noticed the heavy white and yellow wires always seem to be the motor leads, but not sure about the rest.

I did a search and I think this is a diagram that you had posted some time ago John:

But there's no pin out for the plug connector (you know, pins 1 thru 10).

I guess there's not a real "standard" as such.  My RailKing Imperial 0-6-0 had a lamp for firebox glow and cab light, but I don't see them on the diagram above.  How does MTH handle assigning pin numbers to extra features like those?

The Imperial stuff typically has a mux board to bring the extra signals in without extra pins.  Many of the Premier models also use the mux board.

Bob, No it still is not standard, because all the variations I mentioned come in to play.  BUT yes, PS-2 3V tend to be more standard because all PS-2 3V steam have the board in the tender except things like standard gauge and #1 gauge.  The main difference between PS-2 3V steam with MUX and without is the use of the purple wire on Pin 1.  It is a Headlight or Interior wire on Non Mux and it is a MUX signal wire on MUX versions.

There are variables though.  For example switchers with a forward coupler usually do not have a pickup roller and therefor the Red is repurposed as forward coupler.

As far as lights go, on simpler RK a Headlight, fire box and cab light may all be on one circuit (Headlight) or if MUX board involved one circuit can control two outputs.  In that case HL is separate and Cab light and firebox are together.  ONLY 10 wires available.

Wht and Yel for Motor, gray and green for smoke fan, Brown and purple for Smoke heat, Red and Black for AC power, Gray, blue and orange for Tach, purple and blue for Head Light.   Gray is doubled up and so is purple.  Doing the math that is 11 wires required.  That is why purple PV is generated from motor lead via diode under the engine PCB or directly from diodes on motor or even smoke unit on some models (Ten Wheeler).  That way only ten wires needed.  G

Thanks George!  I've got a couple of those engine PCBs with diodes on them, wondered what they were for.

Bob Delbridge posted:

Thanks George!  I've got a couple of those engine PCBs with diodes on them, wondered what they were for.

No problem.  All PS-2 3V and PS-32 Steam Upgrade kits and PS-2 3V starter set engine are wired the same.