What I want to do is by-pass the thermal switch so I can MU two Dash-9s together and run them off the same battery powered “Trackside TE.”
Steve is it an Aristocraft??? I’m guessing either it is not or if it is the MU plugs have already been removed??? ON an Aristo dash 9 there are approximately 10-12 screws to remove and the 4 I believe on the fuel tanks. Not hard at all with a magnetic type screwdriver or if you get em loose then have a magnetic telescoping wand like I have to pull them out. Not hard at all. I think Paul Norton has that with pics on his website too. I just pulled apart a pa/pb and mu’d the a&b together myself, and have done numerous Aristo dash 9’s, and a couple of Mallets. here is Paul’s website link, I used it on doing my Pa/Pb also Steve!! Lots of good info on his site!! Regal
Tx, Jerry, I’ve printed it out. We’ll see. 
Sledge hammers work well.
If it is a new dash-9, it already has the MU plug on it. No take apart needed. Just select “Battery” from the switch, plug in and go.
John Bouck said:Unfortunately, according to Marty, it doesn't work that way. The aforementioned thermal switch buggers the works. That is why it has to be bypassed. It will still protect the individual locomotive, but the bypass allows uninterrupted power to reach the next loco.
If it is a new dash-9, it already has the MU plug on it. No take apart needed. Just select "Battery" from the switch, plug in and go.
Well, I got the body off. The next thing I want to do is bypass the thermal switch that protects the electronics from overheating, but also shuts off one of these contraptions after a few seconds, despite the destructions stating that you can MU them together. I want to run a wire from the attachment of each MU plug to the other one. Marty did this, I have his email somewhere. Hes caution was to make sure that I maintain polarity. I’m pretty sure that I have it figured out, but want someone to give me a second opinion. (“Yeah, yer ugly, too” doesn’t count.) One other thing, I will be running these two Dash-9’s from a battery trail car with the trackside TE in the battery car.
Do I connect the mu cables port to port, or port to starboard? My wife says I can be obtuse, so let me try that again. The hot wire comes in on the port side aft. Do I connect that side to the port side forward, or do I cross over to starboard side forward?
I’ve never MU’d Dash-9’s, but have done Aristo RS-3’s. I don’t do nautical terms well. I maintain the color from loco to loco. So red on the front loco’s cable connects to red on the rear locos cable. I don’t remember if this required crossing the colors on the plugs I got from All Electronics. I’ve since covered all that up with heat shrink.
And Yeah, you are still ugly, but so am I 
Steve
The Aristo MU plug will only allow you to plug it in one way. That should be red to red black to black. dosn’t matter if its the front plug or the back plug on the loco. They ae waired inside the loco to account for your cross overs and such. Your making the jumper should not effect any of that wireing at all.
Worried there is a easy way to test. Take one loco plug it into your batt car and test the direstions then plug your batt car into the front of the second loco and and test the directions on it. They should both work in the directions, wheels moving the way they should be. Then plug your two locos togather and test. Side note. Set the locos on a block of wood or something so the wheels are off the ground why your doing this testing. If the two locos DO NOT go the same direction when plug togather you just swap one of the MU plugs from Loco to Loco and you will be good to go.
Its easy I helped Jerry with his PA/PB set up.
Thanks, Geoff.
You mean you couldnt find anything on youtube 
LOL
Steve Featherkile said:
What I want to do is by-pass the thermal switch so I can MU two Dash-9s together and run them off the same battery powered “Trackside TE.”
Now were playin’ with dollies!!!
Steve,
While you’ve got that Dash-9 on the bench (assuming it’s an Aristo) any chance I can get you to measure the axle center spacing and wheel diameter on the trucks? That particular engine isn’t on Scotty’s spreadsheet… unless the SD45 and the Dash-9 use the same trucks and wheels … do they?
Thanx,
Matthew (OV)
Be advised that the -9 pigtails were wired back to front of other AC locos. You can MU -9’s together, but if you try and add anything else to a -9 consist you MAY need the magic smoke replenishment supply handy.
Matthew.
The answer is yes. …and so does the E8.
TonyWalsham said:Now I understand. I needed to make jumper MU cables for my RS-3's. So the -9's just plug together. So that that forcse you to run them Elephant style?
Be advised that the -9 pigtails were wired back to front of other AC locos. You can MU -9's together, but if you try and add anything else to a -9 consist you [b]MAY[/b] need the magic smoke replenishment supply handy.
Jon Radder said:It shouldn't. Trons don't care which way the loco is facing.TonyWalsham said:Now I understand. I needed to make jumper MU cables for my RS-3's. So the -9's just plug together. So that that forcse you to run them Elephant style?
Be advised that the -9 pigtails were wired back to front of other AC locos. You can MU -9's together, but if you try and add anything else to a -9 consist you [b]MAY[/b] need the magic smoke replenishment supply handy.
There were some SD-45’s where the pigtails were only isolated from the track via the switch on one side. That was fine for nose to tail running. Not so fine if they were run back to back or nose to nose. It was possible to short out the pigtail wiring to the track even if the switch was set to battery.
Steve, it does. The trons don’t matter for wheel pick ups only. Because the pigtail wiring is arse about face, it does matter.
TonyWalsham said:Not trying to hijack the topic... and I probably shouldn't ask questions I really DON'T want the answer to, but I can't help myself.
Matthew. The answer is yes. .........and so does the E8.
So… it’s Aristo’s contention that an SD-45, a C-44-9W, and and E-8 all had the same axle spacing and wheel size?
Yes, yes. Shutting up and going back to my corner.
Matthew (OV)