Electrical issue

SLIKSKILZ

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Looking for any help! Thanks in advance.
06 Mustang GT- With car running- Turn on headlamps and driver side is dim. Then use a turn signal and car shuts off. Using only headlamps or signals it runs but when both are used simultaneously the car shuts down. Don't know why drivers side headlamp is dim all of a sudden or why the engine shuts off when trying both the headlamps and turn signal.
 

stkjock

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have you checked anything yet?

first place I'd start would be the alternator and battery.
 

SLIKSKILZ

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Voltage at junction box and battery while running fluctuate between 14.2 and 14.3. I'm not sure what else to test or how to.
 

07gts197

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Retest but watch battery voltage when you turn on any accessories. I agree with stkjock it sounds like a battery or alternator issue, probably alternator.

My 02 gt did this when the alternator went dead. It ran fine until I turned the ac on then it would die. Any sort of load on the electrical system would kill the motor.
 

SLIKSKILZ

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This is frustrating. Alternator has less than 1k miles on it. I still have factory one that tested good off the car. They both test good off car but fail on car. So it sounds like wiring. Here are my mixed results. I now test the car at 13.6 to 13.7 engine on. Draws another .1 to .2 with an accessory on. Headlamp switch on and turn signal to the right the car still runs. Turn signal to the left and it shuts down. With car off and the headlamp switch on the car will not even start. Just turns over.
 

SLIKSKILZ

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It also still charges the battery. Battery is never low. And to my knowledge the voltage should rise as your rpms do, but that's not happening.
 

cavero

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This is frustrating. Alternator has less than 1k miles on it. I still have factory one that tested good off the car. They both test good off car but fail on car. So it sounds like wiring. Here are my mixed results. I now test the car at 13.6 to 13.7 engine on. Draws another .1 to .2 with an accessory on. Headlamp switch on and turn signal to the right the car still runs. Turn signal to the left and it shuts down. With car off and the headlamp switch on the car will not even start. Just turns over.
What kind of alternator? Most of the replacements are junk, rebuilt Motorcraft or aftermarket. I've read lots of threads about people having to replace a "new" alternator a month after getting it. The only one that seems to be reliable is a Motorcraft 3 phase alternator from the 2010 4.6L. It almost bolts right up.

Your original one could have a bad diode and still test OK on the bench.

What's your battery read with the car off?
 

SLIKSKILZ

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Battery reads 12.4. And thats after starting it and killing it over and over at least 10 times today. I havnt had low voltage in over a year...which is how long this alternator has been installed. After replacing the alternator I found a spot on the old cable that had rubbed thru and was grounding out. Installed new cable and its been fine since then. I believe I have 2 working alternators and the cable was the issue. I am currently going over wiring to try and figure this out. I am hoping it is a ground issue(if it's possible to cause this issue). Whichever relay it belongs to clicks when I turn on the headlamp switch. I do not remember hearing it click before. The most recent thing done to the car was deleting the ABS wiring. There are a pair of wires (white/light green and pink/light green). Those wires go to pcm for charging system. I simply cut them from the connector and reconnected those ends closing the circuit as if the ABS was never there. Nothing else needed to be kept. Dash says check brake system of course but that's all. Everything was joined, soldered and sealed. The car is minimal. No abs, power seats, ac or heat, radio bla bla bla. Has cluster, headlamp switch, hazard and cluster info switches and WOT box. Standard tranny. What's left is whats needed. After many many hours of going thru wiring and diagrams this "light on/engine dying" is the only problem I have come across. It is a PIMA. Any other suggestions would be great. If not solved soon it will have to go to a shop and we'll see what they say. I do NOT believe it's the alternator and refuse to go spend a bunch more $ to "diagnose" the issue. It is probably something I caused. When it comes to wiring I have learned some but still have lots to learn.
 

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