This installation documentation is for the N-scale Athearn Challenger 4-6-6-4. This installation uses the WOW101-Steam decoder, WAUX-KA2, and SM-LED and was performed by Dan M.
NOTE: There are optional steps in this installation.
ADDITIONAL NOTE: This installation requires precision tools and plenty of skill and patience. We do not recommend performing this installation yourself if you are a new or novice installer.
The well-detailed Athearn Challenger 4-6-6-4 shown prior to installation.
To start the installation, flip the locomotive onto its roof and examine the rear of the tender. At the rear end of the tender you will notice there are two screws and the coupler. Remove the coupler and the two screws at the rear of the tender and set them aside. It is best if you use a magnetic tray or small re-seal-able container to ensure these small parts do not get lost! With the screws removed from the rear of the tender, the rear faceplate of the tender will pop off.
After removing the rear faceplate from the tender, next turn your attention to the top of the tender. In the front, there is a plate which must be removed to expose one of the screws holding the shell on. Using a small flat screwdriver, get underneath the plate and gently pry upward. It will pop off exposing the screw.
Remove the screw from the tender shell as shown.
There is a second screw holding the tender shell on. To remove it, first remove the rear-most hatch as shown. It will simply pull off. We recommend using a pair of tweezers and pulling straight upward to avoid damage to the part. Under the hatch you will see a screw. Remove this screw to free the tender shell.
With both screws from the top removed as well as the rear faceplate, the tender can be slid backwards to remove it. Start by pulling outward on the front of the tender's sides to release it. The tender will slide back slightly and stop again. In the rear, there is a crossbar which will catch on the frame of the tender. To release this crossbar from the frame, use a small flat screwdriver and lift upward on the crossbar. Once the bar is up and over the tender frame, the tender shell is free to slide.
Slide the shell all the way back and off the chassis. The faceplate on the front of the tender can also be removed.
To remove the factory decoder or light board, remove this single screw as shown. Be sure to unplug the harness at the front of the decoder.
In order to fit the WOW101 decoder into the shell, it is necessary to trim this center post down. Using a pair of cutting pliers or small Dremel tool, clip the post to the same level as the speaker enclosure so the decoder will sit low enough to clear the tender shell.
Optional Step: In our model, there was an electrical short present in the factory wiring. We determined the cause to be from the track power pickups on this leading truck on the tender. The track power pickups were touching the spring intermittently and shorting the rails to each-other. In order to fix this, the truck was unscrewed and the wires un-soldered so that the track power pickups could be trimmed. Once trimmed back, the wires can be soldered back on and the truck reassembled. No more shorts!
Next we will attach the harness for the new decoder to the existing wires from the engine. We clipped one wire at a time to prevent wires from being crossed. See the diagram below for the pin-out of the factory connector. If you plan to continue to use the reverse headlight, DO NOT cut the Blue and Yellow wires!
This diagram shows the factory wiring from the original connector. You need to splice the wires for the new decoder onto the wires from the locomotive as shown.
The WAUX-KA2 harness will need to be trimmed. It is not necessary to have the Brown, Pink, or Tan wires, so they were clipped back. DO NOT trim the wires flush with the connector! This will make removing the harness next to impossible if necessary in the future. The speaker wires were also trimmed back and then soldered to the factory speaker. Once both harnesses have been installed, plug them into the decoder. Place the decoder in the orientation as shown, with the bundle of wires beneath the decoder. Also ensure that the decoder is pushed forward against the front post for a proper fit. We used Kapton tape to secure all the wires and the decoder in place. Double-sided tape was used to secure the KA2, but we found it nestled in place nicely even without it.
The factory DCC board had a reverse headlight LED installed which was removed when the board was removed. We will be replacing the reverse light by using one of our SM-LED's. These steps are OPTIONAL. To start off the work, we placed a piece of double-sided tape down and stuck the LED to it. We then tinned each pad on the SM-LED.
IMPORTANT!!! Before soldering wires to reverse light, run the wires through the shell above the crossbar. It is not possible to install the shell or rear faceplate unless these wires are routed through the shell first. Solder the BLUE wire from the decoder to the Anode of the LED, and the YELLOW wire to the Cathode of the LED. The arrow on the LED points toward the negative Cathode side. Once the wires were soldered, we used tape to hold the LED in place on the lens in the tender while applying hot glue. It is best not to apply glue directly to the LED or the lens, so we glued the wires to the inside of the rear face plate.
It is necessary to add a resistor in series with the LED. We cut a section of the Yellow wire and installed a 1K Ohm 1/6W resistor.
See here the resistor installed and shrink tubing applied.
This is how the final assembly with the LED should look. To replace the shell, simply slide it forward and it will clip into place. It may be necessary to spread the sides of the shell near the front for a proper fit. The front faceplate can be replaced thereafter, followed by the rear faceplate.
Now replace all of the screws and the rear coupler. With all of the screws back in place, you can re-install the cover plate on the front of the tender, plus any detail parts that you removed (or that broke off!).
With the reassembly complete, your N-scale Athearn Challenger is WOWSound-equipped and ready to impress all your railfan friends!