* SOLVED *One dim headlight, anyone test voltages before?

[idosubaru]

I got an inspection ticket for this, so it's time to get it done right. I'm trying to find out why my P/S headlight is very dim, almost out. I was reading voltages and got a zillion numbers but don't know what they mean and the wiring diagram is confusing me, i'm not getting anywhere.

 

One interesting note: when i unplug the D/S light the P/S light goes out. If i unplug the P/S light though the D/S light stays on? what does that mean?

 

anyone know how to test the 3 terminals and what i'm looking for? lights on, lights off, harness plugged in, not plugged in, one side plugged in, one side not...lots of options.

[idosubaru]

if anyone thinks they can make sense of this.....here's the measurements i took:

 

all measurements were taken with the harness that i was measuring being disconnected. i was too dumb to try to measure it while connected! I'm calling the low beams and high beams A & B because i can't tell which is which since the inside indicator doesn't work. setting A is either low or high and B is the other. A is the same setting for the P/S and D/S measurements.

 

P/S (p/s disconnected for all of the following)

 

Lights OFF , D/S disconnected..................12.19 / 12.20 / 12.20

Lights OFF , D/S connected......................11.84 / 0 / 11.84

Lights ON (setting A), D/S connected..........1.72 / 11.48 / 1.69

Lights ON (setting A), D/S disconnected

Lights ON (setting , D/S connected.........11.58 / 1.32 / 11.58

Lights ON (setting , D/S disconnected

 

 

D/S (d/s disconnected for all of the following)

 

Lights OFF , P/S disconnected.....................12.19 / 12.20 / 12.20

Lights OFF , P/S connected........................11.84 / 0 / 12.21

Lights ON (setting A), P/S connected............0.13 / 0.12 / 11.97

Lights ON (setting A), P/S disconnected......11.70 / 0.06 / 11.97

Lights ON (setting , P/S connected............0.12 / 0.12 / 11.96

Lights ON (setting , P/S disconnected .......0.29 / 0 / 12.00

[torxxx]

well I ran into this problem with with a 91 legacy last winter. There was a bad ground on the drivers side of the car in the wiring for the lights and that caused all the lighting problems. Subaru runs a circuit counter clockwise (drivers front to drivers rear to pass rear to passenger front) around the car. Thats why when you unhook the drivers side, the passenger goes out. With the drivers side hooked up, its still giving power to the rest of the car which is why the rest of the lights stay on.

 

Your problem may be different, but when we got ours fixed, it was a bad ground wire... just an idea

[idosubaru]

when we got ours fixed, it was a bad ground wire... just an idea

 

what do you mean by bad wire? the actual wire is broke, frayed, insulation gone or bad connection where it's bolted to the car? i'll check them out.

 

i'll check the grounding points tomorrow. what you're saying sounds pertinent.

 

thanks!!!

[torxxx]

it was a bad ground wire at the socket on one of the parking lights.

we chased the problem for 2 weeks at work, and that was one of the last things I checked.

 

Is the tail light dim on the side that the headlight is dim?

[idosubaru]

Is the tail light dim on the side that the headlight is dim?

 

i'm at work, i'll go check in a little bit. if the tail light is dim then that's the same issue you had?

 

thanks a ton!

 

TWO WEEKS, wow that sucks, i better check how long i got on my inspection ticket. thanks again.

[monstaru]

well, the passenger side is at the end of the line.your whole setup runs from...lets say firewallish to just the other side of your passenger headlight.meaning that it is at the end of the circuit pretty much.spin the tips of your test probes a little each time you test.it helps with the connection.your readings are probably ok.check alt connections ,well check all connections you can get your hands on.the wires should be red-white, red-black, and black.one of them is dim,one of them is bright, and the black is ground.which wire did you test with which results?replace the headlight and clean all your contacts.then test it and see the difference.check for loose ground wires in the pin connectors as well.....just my 2 cents

 

this is also from my wiring diagram....86 brat.......

[idosubaru]

Wires were:

Red/Green Stripe, Red/Bluie Stripe, Red/White Stripe

 

i've installed 2 used units and one new unit...all with the same results. off to check the rear tail light....

[rallyruss]

you have an open ground by the readings you shared.

its getting its ground thru the other light right now.

[NorthWet]

Dim lights are typically a bad ground. The ground on your passenger side is probably bad, and it is finding a ground through the driver's side bulb. Which car is this on?

[idosubaru]

you have an open ground by the readings you shared.

its getting its ground thru the other light right now.

 

so one of my grounds on the lighting system is bad, or it could be any ground on the car? i have the FSM, will that show the grounds for the lighting system...i think it does.

 

thanks.

 

and torxx....the rear lights are fine, all identical.

sounds like ground issue and not relay....glad i asked, i would have started looking at those!

i'll check grounds tomorrow.

thanks a ton!

[rallyruss]

Dim lights are typically a bad ground. The ground on your passenger side is probably bad, and it is finding a ground through the driver's side bulb. Which car is this on?

 

great minds think alike? ...hmm

[idosubaru]

side bulb. Which car is this on?

 

XT6

 

thanks! you guys are smoking....woo hoo!

i'll look for that ground.

[suberdave]

your thinking to hard. check your fuse, each light is fused seperatly, and even with the fuse blown it will get a small amount of voltage from the other bulb, this is why if you pull the other bulb the p/s light will go out.

 

~check your pasanger side head light fuse~

 

just an idea!

[rallyruss]

on the 89 the ground for low beam should be the red with black wire. it goes to a splice then to the head light switch. for high beam its the red with white.

seperate grounds for high and low circits.

if the probelm exist with both high and low beam settings then I have to take a step back and say check the relay output and fuse(#8 15amp)

[torxxx]

wow.. this post blew up fast... it most likely isnt a bad relay or fuse.. they are all or nothing. it IS a bad ground. like someone said, its prolly just a dirty contact or a busted wire

[idosubaru]

while i'm stoked the problem is solved and it was easy....i owe appologies for this one.

there was no fuse.

i don't know how that happened, i haven't touched the fuses in awhile?

 

thanks for the help and pointing me in the right direction. crazy shat.

[rallyruss]

nice call Suberdave.:cool:

 

glad you found it and it was a simple fix.

[torxxx]

a fuse?!?! :banghead:

 

I've had a few customers bring their cars to the shop for fuses.. one guy put a new engine in and it wouldnt start. he thought he had a tooth off on the disty or t-belts... hehe

felt bad charging him shop rate on that so he got it for free

[idosubaru]

i hated to admit it....i should have made up some heroic story involving major diagnosis, celebrating all the excellent information offered here and having a champagne celebration.

[monstaru]

like your the only one?

[edrach]

i hated to admit it....i should have made up some heroic story involving major diagnosis, celebrating all the excellent information offered here and having a champagne celebration.

Gary you can still have a champagne celebration; hoist one in honor of suberdave at New Years.

[MilesFox]

check the fuses! there is a left and a right. had a dim light after aquiring a car. i realized it was the fuse AFTER getting pulled over(and arrested) when i realized i borrowed the left side's fuse to replace the ecu fuse

[torxxx]

Miles, - all your stories involve you getting arrested... When are you getting arrested?