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wiring diagram terminal designations


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4 replies to this topic

#1 mountaingoatgruff

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Posted 25 March 2012 - 03:49 PM

I'd like to know if there's a way to interpret the letter designations of switch terminals in Subaru wiring diagrams. In other words, what do the "HF HU HL E" mean on the dimmer/passing switch diagram pictured below and the "HC EL TC" on the headlight switch? There must be a method to their madness.

I want to learn how to understand these letter designations so I can figure out how to merge my 97 Legacy harness with my 85 Brat lighting switches. Some of the wires are easy to figure out by tracing where they go but others are not so plain.

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#2 mountaingoatgruff

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Posted 25 March 2012 - 06:00 PM

I got this much figured out

for dimmer/passing switch:

HF - headlight flash
HU - headlight upper/high beam
HL - headlight lower/low beam
E - earth

for lighting switch:

HC - headlight circuit
EL - earth
TC -
V1 -
V2 -
V3 -

TC turns on the illumination circuit, V1/V2/V3 are for the illumination intensity variable resistor.

Brat uses a rheostat - 2 wires
Legacy uses potentiometer - 3 wires

Posted Image

Edited by mountaingoatgruff, 25 March 2012 - 07:33 PM.


#3 Gloyale

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Posted 26 March 2012 - 10:55 AM

I got this much figured out

for dimmer/passing switch:

HF - headlight flash
HU - headlight upper/high beam
HL - headlight lower/low beam
E - earth

for lighting switch:

HC - headlight circuit
EL - earth
TC -
V1 -
V2 -
V3 -

TC turns on the illumination circuit, V1/V2/V3 are for the illumination intensity variable resistor.

Brat uses a rheostat - 2 wires
Legacy uses potentiometer - 3 wires

Posted Image


I think that EL means exterior lights. 1st position of the switch.

I think your incorrect about the brat wiring too. Brats are ground switched, just like Legacies.

Edited by Gloyale, 26 March 2012 - 10:58 AM.


#4 1 Lucky Texan

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Posted 26 March 2012 - 10:59 AM

maybe TC is the instrument cluster/dash lights?

#5 mountaingoatgruff

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Posted 27 March 2012 - 01:19 PM

I think that EL means exterior lights. 1st position of the switch.

I think your incorrect about the brat wiring too. Brats are ground switched, just like Legacies.


EL is a ground, its in the wiring diagram and I verified by tracing wires. TC is illumination including dash and exterior lights as 1 Lucky Texan suggested.

Brat headlights are ground switched but illumination is not. IG switch turns on two lighting relays which then transmit battery power from FL1. One lighting relay powers RH headlights through 15a fuse 9 and the dimmer switch then lighting switch transmit ground to turn on RH headlight. The other relay powers LH headlights though 15a fuse 10 (grounded same as RH to turn on) and lighting switch terminal B through 15a fuse 11. In positions I and II terminal T transmits power to parking/license/tail/certain interior lights which are all hardwired to ground and to dimmable interior lights which then ground through the rheostat to control brightness.

The Legacy switches ground for all lights. To accommodate that I changed terminal B of the Brat switch to a ground and powered the lights accordingly through the Legacy harness.

Then there's the parking switch. In off position the parking switch transmits Ig switched and lighting switched power from the lighting and illumination relay (FB26) to the fuse for parking/exterior lights (FB33). In on postion it transmits battery power (FB27). To delete the parking switch, string a wire between FB26 and FB33 and hack the battery murderer out of the harness.

Does anyone know - in a 2nd gen Legacy when the Ig is off and parking switch is on do the license plate lights come on? Just curious




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