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Super Moderator (Actually a SuperSpy)
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Discussion Starter · #1 ·
Hello, I am adding driving lights to a bugeye.

I want to wire them so that the HIGH (main) beam triggers the driving lights.

I *think* both leads must go through the relay bc of Subaru’s earth switching setup. There used to be a diagram.

Anyone have a schematic?

Thanks!
 

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Water.....sometimes waves
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Sorry, can't help with a bugeye schematic. But what is this "earth switching" setup???? Never heard of such a thing. Am curious what it is......
 

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Discussion Starter · #3 · (Edited)
Sorry, can't help with a bugeye schematic. But what is this "earth switching" setup???? Never heard of such a thing. Am curious what it is......
The bugeye models including the WRX and the STi RA Spec C use a halogen HB5 lamp bulb (correction: there is market-specific H4 also but it's still a single 3-prong bulb). There is one bulb per headlight and it has two filaments, one for dipped (low) and one for main (high) beam.

When the main beam is on and I connect a test lead to the battery, there is a wire on the harness that has earth and the other two have a live circuit. So I think both filaments are constantly connected to the positive side of the battery and the car switches earth.

If so, and unless I'm hallucinating, this means that to set up a relay and have the switch in the car act as a master for the driving lights, only allowing the driving lights to be on with the main/high beam on the stalk, then I'd have to do:

+ side from high beam connector on car to power on driving light switch (my trigger)
+ output from driving light switch to 85
earth from high beam connector on car to 86
+ from battery to 30
+ output from 87a to driving lamps

and then make a connection from the driving lamps to the chassis to complete their circuit.

That's my plan. I *think* I need to run both wires from the car's headlight high beam harness to the relay (with the + running through the switch) or else I won't be able to use the stalk to control the lamps. After staring at something EJ257 kindly shared and making faces as if I understood it (who am I fooling?) I also *think* I need a diode to prevent back current through the DRLs.

Anybody confirm:
(a) my general scheme above
(b) whether I need a diode and if so, what value (I know this is an empirical question but I don't know from circuits).
(c) the the "central" wire on the car's headlamp harness (at the bulb connection) is COMMON + for both filaments, and the other two are switched?
(d) when I stare at the lamp connector on the car's harness, the LEFT side is high beam +?

Thanks!
 

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Water.....sometimes waves
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I love these kinds of challenges. BUT they are hard to solve with words, on a screen. I would need a sketch of what u found at minimum. And when you say one earth and 2 hots with the mains on, is that with everything connected up pr are u checking with the connector unplugged from the bulb?

If u have time we can figure this out.
 

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Discussion Starter · #5 ·
Thanks!

Hemingway write time is the one thing we have not of.

I do have EJ’s diagram (thanks again!) and this weekend my work (and working!) is cut out for me!

I’ll update.
 

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Discussion Starter · #6 ·


I *think* I need a diode to keep the high beam indicator on the dash and the DRLs working correctly?

If so, where, and in which orientation?
 

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Water.....sometimes waves
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So, if in the first diagram those wires from the switch to the high beam bulb are tapped/spliced into the existing wires with no original connections changed, this will work just as u have it. No diode needed.

Furthermore, the positive (hot) wire to that switch can come from any 12v source - it doesn't have to be from the high beam hot. The high beam's - (ground) will control things regardless of hot source for your new lights.

This is all if the oem wiring is what the 2nd schematic shows.
 

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Discussion Starter · #8 ·
Thanks!!

I’ll give it a go and see what happens.
 
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