It should be an LED in the pole. So, polarity matters. If you wire the pole up aand it doesn't work, reverse the wires.

 It usually means dirty track , wheels or both. Could also be a bad connection to the decoder.

You'll need to remove the board installed from the factory. A Loksound 5 nano will have to be hard wired in. Loksound has a ge sound file, but it's for a 44 tonner. If you order, you have to have the file loaded into the decoder. Digitax has a N scale sdXn147ps. With this you need a pr3 or pr4 to down load a sound file. Digitrax has one for the  45tonner.

According to Soundtraxx, 10 light blinks means the deocder is getting too much voltage. Get a meter and measure the voltage at the track. Should not exceed 20 volts. There is no reset button. What power pack are you using?

 Hey Mr. Bach-man, any word on when the HO GE44 tonner with sound will be here?

 It looks like the cab roof comes off. Looks like a tab on each end holds it in place.
 https://www.bachmanntrains.com/home-usa/dwg/dwgs/H502X-IS001.PDF

No.

What brand DCC controller?

 No. The chasis for the FT-A is wider then the other 2. The GP30 is a split frame and had a triangle shape at the end. The GP7/9 frame is atraight across at the end.    Joe

This is for a TCS hard wired decoder. It will work with any 8 wire decoder. https://drupal.tcsdcc.com/installation/ho-scale/1215                 Joe

Do you mean this guy? https://mrdccu.com/index.php/mrh-mag

On my Bachmann diesels, the wires are stranded. I noticed they broke easily from the trucks when I added sound decoders.   Joe

I say no. The I/O port is for the discontinued walk around companion. The 44212 is a DC controller. Don't mix DC and DCC.

You need to be more specific. Steam or diesel?Is 3500 a model number or road number?
 Go here for diagrams  https://estore.bachmanntrains.com/index.php?main_page=index&cPath=68
 

Hey Bach Man, any idea when the sound value GE 44 tonner will be available?