MTH 4-4-0 Jupiter 20-3389-1 Sound Works-No Motion

Losing the data line from the tender through the drawbar. Either not seated fully in the tender, bad drawbar or the receiver pins in the tender have spread and not making contact with drawbar (latter, least likely).

Hi Jon G,

I replaced the drawbar with a new one and same issue. What might be a good next step: Check the receiver pins in the tender?

More likely the wire harness in engine that connects to draw bar.  But either side could be issue.  Also resistor in data line in tender under heat shrink could have broken.  If you have another PS-3 steam you could test engine with that tender, vice vera to find out which is not working.  Engine or tender. G

An update. I have both the Jupiter and 119 from the same year. Switched tenders and the Jupiter fired right up and ran just fine. So it’s something on the tender side. So I’m assuming to check all wires and push them into the connectors to make sure they’re seated all the way. Any other ideas or areas to look for?

Resistor under heat shrink.  The issue is somewhere in the 6 pin harness at tender swivel that plugs into the drawbar, and the other end into the tender board.  G

Replace the drawbar.

Scott Smith

It is not the drawbar. He ran the engine (with drawbar) with a different tender and it worked.  So the fault would be in tender.  G

Hi G. Which resistor are you referencing?  Is it under the board?

@VThokie Steam Fan posted:

Hi G. Which resistor are you referencing?  Is it under the board?

OK, so you see those colored wires coming up from where the drawbar plugs in, then going up to the bottom of the board in a 6 wire connector??

Yeah, that wiring harness- in the middle of one of those wires should be a resistor under heatshrink.

@GGG posted:

Resistor under heat shrink.  The issue is somewhere in the 6 pin harness at tender swivel that plugs into the drawbar, and the other end into the tender board.  G

From MTH parts https://www.mthpartsandsales.com/shop/search use keyword harness for main search and then refine the list using "dra"

Again, notice my first part of the search, I only use a single word "harness" to bring up a huge list, and then refine that list by typing in this block on the results page

In this photo, you can see the resistor in series spliced into the light blue wire.

the cheapest one is also just the long one (in this harness, the resistor is in the green wire under black heatshrink.

Thank you so much Vernon!

@VThokie Steam Fan posted:

Thank you so much Vernon!

Again, most likely, you don't have to replace the harness, it's just when the factory solders those resistors in line, the solder joint isn't good and flexing of the harness as the drawbar flexes left and right when the engine goes around a curve can put stress on the wire. A simple fix, just inspect, put a fresh piece of heashrink over the wire first, solder the resistor to the wire, and then slide up the heatshrink and cover the connection.

That is one area.  Also can have a connector pushed out of the holder in that drawbar area.  Or a bad crimp.  G

I checked and there are no resistors in line with any wires. See picture Below. Should I love onto checking the pins and crimps?

I'm asking out loud because a quick search of service bulletins and I could not find it- is this one of those engines where there should be a resistor in the harness and wasn't, and there was a mod to add one, and if you failed to add that resistor, then it could take out the board?

Reviewing the topic, the OP tested this engine with a different tender (something I typically advise against) but the engine ran, which would point to the boiler board and the engine side of this (wiring, drawbar) to be intact and functional.

At the same time, there is not much here in the tender (that we thought was the problem and what to troubleshoot)- straight 6 pin harness to drawbar mount. Further, the board according to the first post, still makes sounds. So that would imply we have a lost connection of serial data on this line between tender and boiler board.

Again, I thought maybe I remembered a bulletin- but if the board is damaged- well that's all she wrote.

I think you may be at a point a tech probably should look at this.

Would it be worth purchasing that short harness from parts? Or does anyone know the resistor specs and I can solder one inline and test it out?

@VThokie Steam Fan posted:

Would it be worth purchasing that short harness from parts? Or does anyone know the resistor specs and I can solder one inline and test it out?

If the resistor is not there, and you attempt to test and run the engine- the resistor's purpose in life is to reduce and limit current. When it's not there the theory is it burns out the serial data path between tender board (that makes the sounds and makes the decisions) to the boiler board that controls the engine side functions (motor, smoke, lights).

Again, as I remember the bulletin or modification warning- the lack of a resistor results in unrepairable board damage.

Your symptoms are basically mimicking that damage. Engine runs fine when plugged into a "good" tender. Tender makes sounds but engine is dead. Harness in tender missing resistor, otherwise looks good.

@VThokie Steam Fan posted:

An update. I have both the Jupiter and 119 from the same year. Switched tenders and the Jupiter fired right up and ran just fine. So it’s something on the tender side. So I’m assuming to check all wires and push them into the connectors to make sure they’re seated all the way. Any other ideas or areas to look for?

The engine side of this was tested by you using another tender- the engine, all wiring, the boiler board, the wire from boiler board to drawbar, and the drawbar because it's attached at the engine side mechanically.

However then, this tender does NOT work with this engine and does make sounds but engine sits idle when this specific tender is plugged in.

Yes, as pointed out, it could be:

@GGG posted:

That is one area.  Also can have a connector pushed out of the holder in that drawbar area.  Or a bad crimp.  G

Again, what is being said here, is take apart the metal drawbar end (just held together with screws to capture the electrical connector and wiring harness and further inspect. Check both ends to ensure the wires and metal connectors are fully 100% seated into the sockets and all crimps look good.

But the reality is- if it's not the harness- then there is potential that board is damaged. That would be tested by a tech on a MTH PS3 test platform (I do not have one of these).

MTH parts has a $10 minimum shipping per order.

So, sure the harness is relatively cheap, That said, this is a 2 rail / 3 rail switchable engine- hence the brown, black, red, and grey wires in this harnes and the 2 rail/3 rail switch. So just changing the harness in this engine requires  soldering those connections correctly.

And, you want your replacement harness to match wire colors, so that means this longer harness.

Further, if this engine from the same series was without resistor- what about your OTHER engine from the same series- if no resistor in the harness- not good and potentially could result in same problem??? Again if one engine tender is dead, could a similar problem exist in the other?

This right now has be unboxing and checking my own Jupiter.

Further checking all my Premier 4-4-0 PS3 engines, every single one has a resistor in series in the tender harness. Mine are later runs 20-3594-1 (B&O), Strasburg 89, 20-3780-1 and 20-3781-1.

On these later runs, it's the green wire.

In YOUR harness it's the blue wire:

The connector is 2 rows of 6 pins. The wire in the middle in the back row nearest the mounting boss for the entire drawbar is  nearest and directly inline.

The resistor is Yellow, Violet, Brown, Gold =470 Ohms 1/8th Watt.

Also, found this reference to some of what I have been saying. https://www.mthpartsandsales.c...shooting%20chart.pdf

My Premier 2-3-1 Pacific or 241A Steam or Railking
Imperial S2 Turbine is operating intermittently.
STOP RUNNING THE ENGINE!
These 3 specific engines might require after-sale instillation
of an added resistor. Please reference the Service Advisory
for more information. The wire going to pin 4 needs an
added 470ohm resistor. In the 2-3-1 & 241A models, this
wire is BLUE. In the S2, it is GREEN.
As always, please call MTH Customer Service should you
have any questions.
--------------------------------------

Again, in your harness, the Blue wire color is this pin and yours clearly does not have a resistor in series.

Maybe it's possible it's installed in the engine side of the harness, but the symptom of possibly damaging a tender board is what happens if there is no resistor. Worse, you may have 2 engines the same way, one failed, one has not yet failed.

Again, honestly from me to you, I hope I'm wrong, I'm hoping it's just a wire not seated.

At the same time, I'm doing the research and finding and linking info- because there is a small chance, hopefully small, that while some engines were identified with this issue per the above the warning, there may be others it applies to that just did not get identified.

What I do know is, I personally would install the resistor in this engine which likely in and of itself isn't going to fix the problem, but if it protects against future board damage (the replacement board), cheap insurance. At the same time, also, you have another engine of the same run, so the same rules apply to it.

Also, the board possibly needed is out of stock AC0000013

A tech might be able to modify a standard board and relocate the capacitors, but more work.

Again, one of the other techs who have the certified MTH PS3 test setup might be able to help you more.

Interesting that model did not have it.  So it is possible that the tender board functions but can not communicate with the engine.  I have run into one of those faults.  So the board  can be tested on the bench tester to see if it is functioning.  The harness should have the resistor.  That can be added to your harness.  G