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Ok this really has me mystified. Here are the symptoms: if I turn on my headlights, my left turn indicator will stay on 100% of the time (both front, rear, and dashboard light). If I turn off my headlights and use my left turn indicator, all lights (taillights, interior accessory lights, but not headlights) will flash.
-If I remove the fuse for the turn signals, the left turn signal light will remain on when headlights/taillights are on.
-If I remove the taillight fuse, the tail lights will blink when I use the left turn signal -If I remove both tailight and turn signal fuse neither will illuminate under any circumstances
So I feel like there must be a short where left turn signal light wire is touching something else, since tail lights get power when the fuse is out if the turn signal is used, and turn signal illuminates if lights are on.
Now how the heck do I figure out where this is happening? The only wiring I've changed on the car is adding a stereo (2 years ago), but since the symptoms have to do with left turn signal, I don't think it could be related to that. I don't see anything obvious when looking at connections under hood. How would a mechanic go about solving this? From Googling it seems like it could be the multi-function switch or a ground, but I'm not entirely sure how to debug the ground, and don't want to just buy a switch without proving that's the problem first.
You could bypass the multi-function (combination) switch by jumping the appropriate circuits. There’s a 16 pin connector behind the steering column area.
If you jump the circuits and everything works correctly then you need a switch. If not, I would start looking at the connector for damaged wires, terminals, and the ground.
The ground for it is behind the glove box, on the left side according to alldater.
This will probably be very difficult to find the short. Earlier today I also considered some tests to rule out the combination switch; but, concluded it probably will not be due to the combination light switch. At the switch, turning on the headlights sends a ground signal (-) through the circuit. Turning on the turn signals, sends power (+) through the circuit. So, even with a faulty combo switch, it should not cause what is happening.
Turning on the headlights does send a ground (-) to the taillight relay, which then allows power (+) through the taillight relay to the small light circuit via the Red/Blk wire coming from the under-dash fuse/relay box. There may be a short in the Red/Blk wire(s) to the left turn signal Grn/Red wire somewhere along the Dashboard Harness A. The commonality of the Red/Blk power wires (+) and the Grn/Red power (+) wires are part of Connector L which plugs into the rear of the under-dash fuse/relay box.
By chance, was a taillight assembly bulb replaced sometime before all this happened? If so, check the wire harness at the left taillight assembly for pinched/cut wiring which may be causing the short.
Thank you for the tips! I will try some of these this weekend. Another clue - if I hit the brakes, my turn signal light comes on - that makes me think maybe it's not the multi-function switch? Also I just noticed my front headlight is out, surely that can't be related.
Also - no bulbs or other things have been replaced recently.
Can also be a bad or incorrect bulb causing multiple circuits to be tied together.
Originally Posted by ry0ohki
Also I just noticed my front headlight is out, surely that can't be related.
Personally I would either replace the inoperable bulb, or at least swap headlights and see if the problem persisted - but on the opposite side. Otherwise you’ve got a pretty crazy short somewhere.
Just to follow up I found the problem - I took off the taillight assembly on the side where the problem was happening, and found there was a Uhaul towing harness tapped onto the wires of the assembly. I removed the taps, taped up the wires and it's good to go. So there must be a short on the towing harness (which I never use).
Electrical Issue, How To Debug?
