Nissan Maxima Headlight issue.

[Flying Phil]

I know... not usually the place to ask Nissan questions, but I have an electrics issue... and who better to ask than a bunch of motorheads who have spent years working with British electrics (comparably, Japanese electrics should be a walk in the park).
Each headlight has three wires to the back of it. One gound, one powers low beam, one powers high beam. Why do I measure 12V on all three regardles of weather low or high beam is selected (the light dosen't work in either case)?

[John Scherrer]

Are you measuring this on the connector with the bulb out?

It could be a bad earth .. also modern cars have fiendish bulb/lamp filament failure detection which can mess up diagnostics such as this ..

[AtomMadStew]

measuring on the earth 12v because the consumer (bulb) could be shorting inside (bypassing the filament) and returning to earth?
  Or most jap stuff is earth switched so you will measure 12v on all 3 and its the headlight switch that completes the earth circuit somewhere else on the car (side/dip/main switch) to operate said lights.

[Flying Phil]

Tried two different bulbs, same result (nothing). The low beam was intermittant for a while. I measured the voltage with the connector attached to the bulb. I'll pull of said connector and then measure each wire at low and high beam. I think this should tell me if it's a switch/logic, or a faulty ground. Jees, I hate electrical issues...

[AtomMadStew]

I have full access to Autodata, give me as much info on your car and ill see if I can pull a wiring diagram for you Phil.

[Flying Phil]

Thanks Stew!
2000 Nissan Maxima SE. The headlight has returned on low beam, still no high beam. Haven't had a chance to test what I'm getting yet.

[AtomMadStew]

Sorry my fully licenced Autodata does not show a lot for a car of that age. Nothing in wiring diagrams whatsoever. I do have a buddy technician that works at Nissan so ill see if I can get one out if him.  Was is a 2 or 3ltr? Not that it makes a difference I shouldn't think.