Jump to content
Ultimate Subaru Message Board

Weird headlight issue 1998 Legacy


Recommended Posts

Was wondering if this has happened to anyone before. When my switch is in low beam position. The low and high beam wires have power to them. When you switch to high beam only the low beam has power to it. And when you pull back on the stalk only low beam has power to it. It's like it's reversed? Weird. Anyone have any wiring diagrams? It's really bugging me.

Link to comment
Share on other sites

Yeah the headlamps share common power and are grounded through the hi-lo switch.

You'll have 12v on the wire for the filament that isn't lit, because that wire is not grounded at that time.

Gets more fun when you have fog lamps due to the wiring for the fog lamp relay.

  • Like 1
Link to comment
Share on other sites

Definitely wired correctly. Ballasts, relay harness. Everything.

 

Besides that. Even if I remove everything. And just test for power at the factory socket. It does what I describe. Low beam position. Power on both high and low beam wire. High beam position power only on low beam wire.

Link to comment
Share on other sites

Right side

Red: high beam ground

Black/yellow: 12v supply

Yellow/blue: low beam ground

 

Left side

Red: high beam ground

Red/Blue: 12v supply

Yellow/blue: low beam ground

 

On these cars the Grounds are switched, Not the supply.

 

Bulb unplugged, testing at the factory socket, voltmeter grounded to battery -

Low beam position you will have 12v only on the supply wire.

High beam position you will have 12v on the supply wire, and (if the car has factory fog lamps), will show 12v on the yellow/blue wire if the fog lamp switch is On. With fog lamp switch Off, you should only have power on the supply wire.

 

What will change is continuity to ground. On high beam position, continuity to ground will be on the Red wire.

On low beam position continuity to ground will be on the yellow/blue wire.

Link to comment
Share on other sites

Whenever you supply power to an open circuit (due to a bad ground or open lamp) you will see full voltage at any point on that circuit if no current is flowing. It is best to test for power with the circuit connected up normally. Otherwise you may get confused about the real problem. From you stated about the problem I have to think the light switch is wired backwards somehow.  

Link to comment
Share on other sites

Ok guys I think I have this figured out. I'll update when I verify. But thanks for the help. So what I figure is. Since this is switched ground. And I'm plugged into a premade hid relay harness. It's wired traditionally. Expecting the ground to be where the legacy power wire is. And has a ground where the normal power should be. I think if I just wire this up like a switched ground. It'll be ok.

Link to comment
Share on other sites

Yeah if that harness isn't designed for a switch ground system it won't work right.

You'll probably just need to run a separate power wire for the HID ballast.

The high beam can be connected right to the stock wiring, but if you're doing wire work already I would suggest a relay and separate power wire straight from the battery for the high beams as well. Higher constant voltage at the bulb will give you better light output.

The relay can be right at the headlamp and just use the common supply and high beam ground wires in the factory harness to trigger the relay on.

Edited by Fairtax4me
Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
 Share

×
×
  • Create New...