Both of the used MTH Alco RS-27 I recently purchased had multiple dead 2mm dia. LED marker lamps. The voltage powering these 1997 PS1 vintage markers measured 6 vdc. Since the original 2mm "bullet" shaped LEDs aren't readily available
I did the best I could with the " 2mm Round Flat Top Water Clear LED Diode, Red " available cheaply on Ebay. The red diffused ones that arrived weren't quite as ruby red as the original LEDs ( a bit milky looking ) , so I went with the water clear ones. ( Searching prototype RS-27 photos online showed many had clear, slightly convex marker lamp lenses anyway, nowhere near as rounded as the bullet LEDs. )
With a 6 vdc power supply and resistor substitution box for testing, I settled on adding a 1K (1000) ohm 1/8 watt resistor to limit the brightness to something like a lamp behind a lens, otherwise the recommended resistor for these LEDs and 6 volts dc ( 6v - 2v LED forward voltage ) / .02 amp { 20 milliamps LED forward current } = 200 ohm resistor ) would have made them brighter than the headlights!
I cut off the original LEDs and shrink tubing, stripped the wire ends and added new lengths of shrink tube to the wires to insulate the soldered connection. Then soldered the red wire to the positive input that I had added the resistor to, the black wire to the negative ( shorter leg ) input, tested the LED, slid the heat shrink tube in place and shrank it.
If you don't have the original connector and wiring, look for " 5264 connector " or " 5264 battery connector " on ebay
Installation in the body was relatively easy with long nose pliers since the LED tower is a slip fit in the marker hole.
I mounted the tower end flush with the outside of the body, pressed the LED body into the sticky pad and curved the leads so they didn't interfere with each other. The result looks at least as good as the original units.
One of the headlights had also burned out so I found some similarly sized, wire terminated, 2 volt lamps on ebay and did a similar cut, solder and heat shrink job on them.
The replacement "Clear 3mm 1.5V 100mA rated Miniature Pre-Wired Grain of Wheat Bulbs, Warm White"
https://smile.amazon.com/gp/pr...00?ie=UTF8&psc=1
have a kind of lens on the end of the glass envelope, so they produce a beam of light. In combination with the model's twin lamp housing it does a nice job of focusing the beam. Hope this "How To" helps future MTH diesel owners now that MTH parts will become scarcer.
