DRLs on 03 Silverado

samckitt · September 23, 2003

I noticed on my 03 Silverado the other day that the Daytime Running Lights have 2 elements, almost like the older high/low headlights all in one bulb. So what is the deal? I have only seen one side lit.

Scot

MCourson · September 23, 2003

I think it is for a brighter bulb. I know that all the bulbs in the tail lights of our '94 are double filament because I had to replace a few the other day.

GnatGoSplat · September 23, 2003

It's just cheaper for GM to buy double-filament bulbs in bulk.

They are, 4157 or something like that.

4156 (single filament version) will fit and work just fine.

4157's have an 8W low power filament (for parking lights) and a 27W high power filament that the DRL uses. The 8W filament is not used and the socket isn't wired to use it anyway. 4156's have just a single 27W filament.

I guess the good thing about the dual filament bulb is if a more important bulb (like the turn signal or brake light) burns out, you can swap the DRL bulb into its place.

samckitt · September 23, 2003

My 97 truck the back lights had the dual filaments because the were both the running (parking) lights & the brake/turn signal lights.

I think I will look into turning on the brighter of the two filaments of the DRLs with my brights. So then I will have the Highs, Lows, & the DRLs in bright model ;-)

Scot