DRL's with three wires

[bluehonda]

I have just bought some DRL's from Ebay, round 9 leds, and they have three wires to connect.
Red and black with bullet connectors (obviously +ve and -ve) and the lights seem pretty bright but there is also a longer white wire with just a tinned end.
Can anybody give me an idea what the extra wire is for?
I can ignore it but It's making me curious.

Brad

[ST2UP]

?? Dimmer ?? I have no idea just spit ball'in........

[saaz]

Probably for an optional dimmer. Most DRLs can be adjusted for brightness, especially the LED ones.

Here is a wiring example http://www.clearwaterlights.com/downloads/v5_manuals/Honda%20ST1100%20v5.0.pdf

[atoyot]

Aren't DRL's supposed to be wired to come on whenever headlights are off? If so, I've wondered how cars with auto-headlights go when driving through a tunnel in daylight with DRL's on; should they turn off when the headlights come on??

[saaz]

A good question.  Something to research further, as I am sure there are ADRs dealing with this issue.