Life-Like Proto 2000 locomotives with number board lights have the number board bulbs wired to their 8-pin DCC plug using pins 4 and 5. This causes no problems with DC operation but causes a path from the rail pickup to the gray motor lead when a decoder is installed resulting in erratic operation and decoder failure.
This is a known problem in the Proto 2000 GP60, SD60M and LifeLike GP38-2.
The DH165L0 uses a current limiter set to control one incandescent bulb on the front (FOF) and one on the rear (FOR) and putting the removed number board bulb on either FOF or FOR will result in two very dim bulbs if they light at all, and putting the number board lights on one of the functions will require a resistor defeating the purpose of using the DH165L0.
Aksel Suarez solved his problem by removing the incandescent lamps and using LEDs. He got good brightness on all lights and number boards without using resistors.
Aksel used the white LEDs from Mouser Electronics (mouser.com), Part# 604-wp7104qwc/d, rated at 3.5Volts and installation involved removing the number board lamp, trimming off the headlight bulbs, and bending and trimming the LED leads to fit in the area provided for the original lamps. He then soldered the 2 LEDs together. After tinning the original wires he soldered the lamp common wire from pin 7 (lamp common) to the positive (longer) side of the LEDs and the return wires from pin 6 and 2 to the negative (shorter) side of the forward and reverse LED bank respectively. He then covered the bare elements and connections with liquid electrical tape to avoid short circuits to the locomotive’s frame, tucked the lamps into position and held them in place with a bit of electrical tape.
The result was a well-lit model using a favored decoder with minimum effort.