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Electrical weirdness with left turn signal

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97 OBW AT with a transplanted 2.2

 

New problem. The left turn signal does not work when the headlights are on but does work when the headlights are off. The left arrow is slightly lit up (a light green) when the headlights are on. The right arrow works just fine. Really at a loss to explain this one. SOS. Thanks.

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I believe that the Left Turn Signal Lamp's wiring could have a Short-Circuit nearby the HeadLamp, in the area where all those wires are wrapped together; sometimes that wrapping or the wires, get crushed between parts, and with time they develop short-circuits, so I Kindly suggest you to start searchin' for a Short Circuit, from the Bulb's Socket and continue followin' the Wiring 'till it reaches the Firewall.

 

Kind Regards.

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Possibly a bad bulb. See if it does the same with just the parking lights on.

Check all of the dual filament marker/ signal bulbs on the left side.

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I'll swap bulbs with the other side in the morning and see if that solves it. Would be a lot nicer than tracking down a short.

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Several owners, myself included, have experienced a similar problem that was only cured by replacing the turn signal stalk.

 

Stalk?

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I think you have a grounding problem causing the trouble. A simple way to prove it is to tie a temporary jumper ground wire between the negative battery terminal and to the left rear turn signal ground. If the trouble clears then you know that is the case. You could also check the voltage between those points while the trouble is occurring to see if there is a voltage drop. Normally there should be no voltage drop happening. Clean the battery to chassis ground and also the left rear ground and any other bonding grounds.

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I think you have a grounding problem causing the trouble. A simple way to prove it is to tie a temporary jumper ground wire between the negative battery terminal and to the left rear turn signal ground. If the trouble clears then you know that is the case. You could also check the voltage between those points while the trouble is occurring to see if there is a voltage drop. Normally there should be no voltage drop happening. Clean the battery to chassis ground and also the left rear ground and any other bonding grounds.

 

I was thinking the same thing upon reading the thread. It sounds like a bad ground. Follow what Cougar suggests, and or, create a new ground wire at the turn signal connector.

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I'll start by changing the bulbs, then playing with the grounds, then finally playing with the stalk. That seems to be the most logical and least inexpensive way to approach the issue.

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I'll start by changing the bulbs, then playing with the grounds, then finally playing with the stalk. That seems to be the most logical and least inexpensive way to approach the issue.

 

Well the LEAST inexpensive way I think would be to buy a new car. :-p

 

JK. I agree, bulbs are cheap, new turn signal stalk = $$$. Check cheap stuff first.

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I'm gonna go with a bad ground too. With the headlights off, the turn signal current is going through the headlamp filament to ground, rather than the ground wire it's supposed to be going through. With the headlamp on, the current can't go through the headlamp as it's already turned on.

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I'm gonna go with a bad ground too. With the headlights off, the turn signal current is going through the headlamp filament to ground, rather than the ground wire it's supposed to be going through. With the headlamp on, the current can't go through the headlamp as it's already turned on.

 

Is it as simple as identifying the ground (negative) wire and splicing it onto a chassis ground?

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The ground wire coming from the bulb socket should be black in color. You don't need to splice it. Just follow it until you find the place it makes connection to the chassis of the car. You could try just removing the connection and cleaning the surfaces of the contact points to see if that fixes it. If it doesn't then try running a temporary jumper to the socket body of the lamp and a good ground to see if that changes things. Also clean the battery to chassis ground as that is most likely where the problem is really at. The high current needed for the headlights is causing an excessive voltage drop on a chassis ground.

Edited by Cougar

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I'm gonna go with a bad ground too. With the headlights off, the turn signal current is going through the headlamp filament to ground, rather than the ground wire it's supposed to be going through. With the headlamp on, the current can't go through the headlamp as it's already turned on.

 

This is not how the wiring is done on this model. The headlamp circuits are switched to ground, and are entirely separate from the signal and marker lamp circuits, which are load to ground. The signal lamps are grounded directly to the body. The ground points for the front signal lamps are on the inner frame rails on each side of the car a few inches back from the radiator, easily visible from under the hood.

Rear ground points are in the trunk just below the tail lamps.

Wagon rear ground points are a few inches towards the front of the car, one on each side behind the side panels.

Edited by Fairtax4me

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Even though there are numerous bonds to ground on the chassis this problem appears to be related to a grounding problem somewhere. Making a temporary ground jumper connection to the rear light will easily prove it. The trouble could be with the left rear quarter panel area. There also may be more than one bad bonding connection.

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This is not how the wiring is done on this model. The headlamp circuits are switched to ground, and are entirely separate from the signal and marker lamp circuits, which are load to ground. The signal lamps are grounded directly to the body. ...

 

That is the Reason why I wrote that there 'could' be a short-circuit on the Turn Signal wiring.

 

Also, the Original Poster wrote:

... The left arrow is slightly lit up (a light green) when the headlights are on ...

 

and that made me believe that there 'should' be some kind of interaction between those two Different Circuits: The HeadLamps one and the Turn Signal One.

 

Also, I believe it is related to the positive (+) signal of the Headlamps ... I imagine that Maybe when the Headlamps are 'on', their positive are barely grounding (Like salty Humidity between wires) somewhere nearby the turn signals' wiring, in the lamp's area, but that is not a "Complete" short-circuit... yet, or the fuse would have blown.

 

Good Luck!

Kind Regards.

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This is not how the wiring is done on this model.

 

Okay, I found a diagram here which is for JDM but I'd guess pretty similar:

http://jdmfsm.info/Auto/Japan/Subaru/Legacy%20Outback/1997/Service%20Manual/WIRING%20DIAGRAM%20SECTION.pdf

 

Pages 25, 75, 107, 117 ,118, probably other pages too.

 

So replace my "headlamp filament" words with "side marker filament" then, as turning on the headlamps means turning on the side markers too. Same idea. Anyway it still sounds like a problem with a ground somewhere, I wouldn't be quick to dismiss it just because the headlights are switched to ground. :-p

 

I doubt it's a bad bulb; it would need to fail in a way where both filaments are attached to each other but not to ground. It could be the bulb holder is corroded/broken and not making a good ground connection to the bulb.

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