I've done three of these now and there are two tricks to getting the maximum lighting (which still is not that impressive)

1. solder the two posts together (bypassing the potentiometer)

2. paint the inside walls where the bulb reflects.....paint them glossy white. After a few years, they yellow.

In one of my cars this helped dramatically but in the other two it wasn't so impressive.

Don

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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed