My only advice is verify the ground connection is good. I assume one of the 2 connections to the lamp is ground. You can test it two ways that I can think of. You can test for continuity from the ground connection to a known good ground (chassis/body). Or you can put one lead of your test light on the positive contact and the other lead on a known good ground.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra