One dim headlight

[Gloyale]

FSM shows the following

 

 

LH relay plug as Green 4 poles plug. Wires in it are:

thin Black wire, Relay ground

fat black wire, Ignition 12v

Black w/ white wire, 12v from Fusible link 2(red)

Black w/red wire, 12v output from relay, feeds fuses 6 and 7

 

 

RH relay uses a black plug. wires are as follows.

 

Thin Black wire, Relay ground

Fat black wire, Ignitoion 12v

Black w/ white wire, 12v from Fusible link 2(red)

 

Black w/ yellow wire, 12v output to fuse 8

 

BR and BW wires that feed the fiuse panel are the ones you should check for continuity between relay and fuse.

 

Hopefully this helps locate the relays

[glfarnes]

Update

 

I found the last relay jammed up against the computer and got them all out using a mirror. All the relays are good and the power is normal at the relays, and on through the fuses. I have a really poor diagram, but from what I can tell at this point the ground on the right headlamp must be bad at the switch. I can't think of anything else it could be, since this is a ground to light system. I'll have to wait until after work again tomorrow to check the switch and will keep you all posted. My wife tells me that there are several other Subarus running around the village with the same problem If I figure this out I bet I can win some bets!!

 

Jerry

[Cougar]

Jerry,

 

In a previous post I thought you had said that you measured the voltage on the center lead of the bad light and stated it was low. If that is correct then there is a problem with the supply voltage to the light and not the ground. You can also prove that by placing the meter probe on the ground side of the light and make sure there is no voltage to ground there. If the ground is bad then you will see a voltage drop across the bad connection.

 

I will be able to get to my reference material tomorrow and help you more on this if you need it.

[daeron]

Jerry,

 

In a previous post I thought you had said that you measured the voltage on the center lead of the bad light and stated it was low. If that is correct then there is a problem with the supply voltage to the light and not the ground. You can also prove that by placing the meter probe on the ground side of the light and make sure there is no voltage to ground there. If the ground is bad then you will see a voltage drop across the bad connection.

 

I will be able to get to my reference material tomorrow and help you more on this if you need it.

 

With a problem like this, amperage that the wire can flow is as important as voltage it is showing. If you are showing low volts, then chances are the wire can't flow too high an amperage, either. One way to test this would be to rig up a horn and try using the positive wire from the dim headlight to power the horn; if the horn sounds clearly, then you are getting at least most of the amperage you should have.. but if the horn sounds anemic or flat, then you know you aren't getting good amperage conductivity (ie, built up resistance) in your supply line.

[GeneralDisorder]

You *have* checked that the bulb has a good low-beam element right? Does it work on high's?

 

GD

[Loyale 2.7 Turbo]

...

 

This just gets better all the time!!

 

This is Usual on Subies!

 

Well...

 

I Suggest to Check the Bulb, or test the Wires with other 9004 Bulb, as GD said; but Also: the Last Part of the Wires...

 

Why? ... if the Dim Light is on the Battery Side, maybe it´s Acid Vapors did Corroed the Wires... it is a Possibility.

 

On my Yellow Wagon, a Year Ago; I did have one dim Light too... it was the Plug that connecs to the 9004 Bulb (I use 9104 Rally Bulbs, but That´s another Story ) the Tiny Metal Sheets from the Plug were Corroed, like Burned... (Well... my Bulbs are 100 Watts output... ) but Maybe the same case can be on your Subie, so Check the Plugs "Carefully" too...

 

Good Luck!

[Cougar]

I finally got back to my reference manual (a FSM for a '88). It shows the following info. The power for the headlights is supplied through the red fusible link. The link is tied to the relays and the relays feed fuses 7 and 8. Fuse 8 goes to the right side headlight on a red wire. If the voltage is good at the fuse and the fuse contacts, while the lights are on, but is low at the headlight then the red power wire has a connection problem somewhere. For future reference and to all interested, it is good to know that checking the voltage at the fuses with the lights on, will show if the relays are making good contact or not.

[glfarnes]

Update on the update

 

I have now covered all of the components and found that they appear to be good. That includes relays fuses and switches. Tomorrow I will either start with a horn and use that method to check between components (who said to do that? I don't remember now) or jumper between and find the bad wire if that's the problem like cougar thinks. There is no power on the right headlight tab in the switch. Another strange happening is that the parking lights came on and I had to pull the fuse to get them to go off. I know I'm getting close, and really appreciate all the help from you guys.:-\

 

Jerry

 

ps I just bought a banged up 91 to play with when I'm done with this one!!:-p

[GeneralDisorder]

Another strange happening is that the parking lights came on and I had to pull the fuse to get them to go off.

 

Flip the rocker switch on top of the column - it controls that. You probably accidentally hit it.

 

GD

[daeron]

I mentioned the horn idea, but what did you mean by "no power on the right headlight tab on the switch?" If the switch has two circuits, and one of them is for some reason not being powered, then you won't get any power at that plug to run any horn, headlight, or anything from that right side power wire...

 

Does anyone know offhand in what order power travels from the battery through the wiring and switch, and into the headlights? You basically need to check for power at all steps. Once you find power missing, backtrack through the circuit until you find voltage.. and then you have found where your problem lies.

 

Flip the rocker switch on top of the column - it controls that. You probably accidentally hit it.

 

GD

 

And dont feel bad when you realize you turned them on, it happens to a lot of people. Not ALL of us, but alot of us.

[Cougar]

Does anyone know offhand in what order power travels from the battery through the wiring and switch, and into the headlights?

 

Daeron,

Check out my reply in post #32 of this thread.

[Cougar]

Jerry,

 

 

I sounds like you have proved that the problem is on the power lead between the protected side of the fuse and the center lead of the light. You have 12 volts on each side of the fuse and something much less on the center lead of the light. Make sure the connections are ok on the back side of fuse #8 which should go to the passenger side light. To verify it you can pull the fuse to see if the light goes out. You can also verify, if you want to, that by placing a 12 volt jumper lead to the center lead of the light will make it work correctly. Proving the red feed wire has a problem. My info doesn't show any connector between the fuse and the light so there shouldn't be any possible trouble spot unless the wire itself is damaged. Perhaps the insulation got damaged and internal corrosion has eaten way the wire. If the wire is ok then the only place trouble can be is at the fuse connection or at the light connection of the red wire (provided my info is correct).

 

Something to note. When checking the voltage at the light switch remember, the switch turns on the lights by making a ground connection. So there shouldn'd be any voltage at the switch connection, if the switch is working correctly and the lights are on, since the switch connection is at ground potential. The relays and fuses are on the hot side of the circuit and the light switch is on the ground side.

 

Another important note:

Hopefully I made it clear in my previous posts that all the tests I gave instructions for were to be done while the lights were on. If the lights were off while testing, then the voltage test at the fuses needs to be done again with the lights on. If the voltage is still ok there then the red wire still needs to be checked.

[Gloyale]

There is no power on the right headlight tab in the switch.

 

 

Power for the headlights does not run through the switch. Ground does.Power goes straight from frusible link,through relay, through fuses 7 and 8, then straigh on out to headlights.Red w/Black(RB) wire gets grounded by the switch for Low beams. Red w/White(RW) wire get's grounded for High beams. Instead of testing for power through the 12v side of the cicuit, test for high resistances in the grounding part of system. RB and RW wires at each lamp should have continuity to ground when Headlight switch is in each respective position.

[glfarnes]

I mentioned the horn idea, but what did you mean by "no power on the right headlight tab on the switch?"

 

Dearon,

 

What I meant, is that with the switch opened up and the headlights on, that there is no power between the tab that powers the right headlight and ground. The system is hot all the time, so there should be twelve volts there.

 

It looks like the holiday is going to stop any "fun stuff" this weekend, so I may have to get back to it monday.:-\ I know what I have to do now. I just have to get permission from the "boss" to do it. I think you guys are all too young to know how that is.

[daeron]

Dearon,

 

What I meant, is that with the switch opened up and the headlights on, that there is no power between the tab that powers the right headlight and ground. The system is hot all the time, so there should be twelve volts there.

 

It looks like the holiday is going to stop any "fun stuff" this weekend, so I may have to get back to it monday.:-\ I know what I have to do now. I just have to get permission from the "boss" to do it. I think you guys are all too young to know how that is.

 

 

Power for the headlights does not run through the switch. Ground does.Power goes straight from frusible link,through relay, through fuses 7 and 8, then straigh on out to headlights.Red w/Black(RB) wire gets grounded by the switch for Low beams. Red w/White(RW) wire get's grounded for High beams. Instead of testing for power through the 12v side of the cicuit, test for high resistances in the grounding part of system. RB and RW wires at each lamp should have continuity to ground when Headlight switch is in each respective position.

 

Behold, you should NOT have any power between the headlight switch and ground.. you should have continuity between the headlight switch and ground. It was outlined earlier than my post that you just quoted, in this thread.

 

It's amazing how often we overlook things in a post, and then never re read the whole thread..

 

Oh, and young and uninhibited as we may be, we DID all have parents growing up.. I think we can all appreciate what happens when the boss hands down word limiting our "fun" time.

[Gloyale]

Dearon,

 

What I meant, is that with the switch opened up and the headlights on, that there is no power between the tab that powers the right headlight and ground. The system is hot all the time, so there should be twelve volts there.

 

It looks like the holiday is going to stop any "fun stuff" this weekend, so I may have to get back to it monday.:-\ I know what I have to do now. I just have to get permission from the "boss" to do it. I think you guys are all too young to know how that is.

 

There is no voltage for the lights going through the switch. The only voltage through the switch is for the markers and dash lights. There is a Red w/blue wire at the switch, same color as the Left headlight power wire, but it is not the same wire. The one wire with 12v in the switch is for the marker lights and dash illumination. the switch controls the ground, no the voltage.

 

there is a black wire going into that switch. with lowbeams on it should have continuity to the Red w/blue wire. With high beams on, it should have continuity to the red w/white wire.

[Gloyale]

Cougar suggested running 12v to the center lead of the R headlight. I think this is a good idea. If you run 12v to it, and it then functions normally (ie. bright light, high/low beams work via switch) you have isolated the problem. This would mean that the grounding action of the switch is functioning normally, and your problem is in the Red wire coming out of Fuse 8.

 

something to look at. Shortly after the fuse box, attached to the big red wire from 8, there is a splice where a smaller red wire attaches and supplies power to the "high beam" indicator light. Look for a problem at that junction. just lower the fuse box down to access the wires in the back. Does your "high" indicator come on when you use the high beams? If so then that the circuit is good up to the point that that wire diverges. If not then there is your problem.

 

Because it's acting like it would when the fuse blows, I am still inclined to think you've got no voltage to the headlight. Same net effect as a blown fuse but in this case the break in the circuit is somewhere else. How about testing that red wire for continuity from end to end. Hook a multimeter lead to the center terminal of the headlight plug, and the other lead to the "out" side of fuse 8 recepticle. might need some long jumpers, but that is a sure fire way to find out if that wire is conducting. Then perform the same test from the "in" side of fuse 8 to the Black w/Yellow wire in the relay plug.

[glfarnes]

Just a note of thanks to all that helped on this. The outcome at this pint is a little odd. I hooked up a horn and started running down the system. Honk. Honk. I get to the headlight plug and didn't expect anything, as I'm sure none of you did either, but it honked. I put the headlight back in and the problem was gone. I'm sure that it's just for now, but impossible to find a problem that isn't there. I'm moving on to another project, as I've bought two more vintage rigs. Again, thanks to you all.

 

Jerry

[Cougar]

Glad you got it fixed Jerry. Thanks for the update. If the problem occurs again you will know the first place to check at least.

[Loyale 2.7 Turbo]

...I put the headlight back in and the problem was gone. ...

 

That´s what I Said, the Plug:

 

... it was the Plug that connecs to the 9004 Bulb ...

 

[psylosyfer]

Glad it's fixed!

[psylosyfer]

Can also be caused by a bad relay under the dash, left of steering column.