Headlights went out at the same time?

ManicCasanova

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Mazda Protege 5
This morning on my way to school my p5 drove strange. At 60mph it was at 4k rpm like it didn't shift and the battery light came on. 12 hours later I start the car to go home and it starts fine, no battery light on but now my headlights are not working. Accessory lights work as do my highbeams. Isn't it unlikely for both light bulbs to go out in unison?
 
I was told that if you disconnect the battery with the vehicle started and it stays running it is likely not your alternator. If how ever you disconnect your battery while running the vehicle and it sputters and dies it means your alternator isn't providing enough current.

Any one else check me on this ???
 
I was told that if you disconnect the battery with the vehicle started and it stays running it is likely not your alternator. If how ever you disconnect your battery while running the vehicle and it sputters and dies it means your alternator isn't providing enough current.

Any one else check me on this ???

It's a very outdated test. If you try it on a modern vehicle, the alternator can produce a voltage spike when you unhook the battery that can damage sensitive electrical components like the PCM.

Parts stores will usually check them for free.
 
...It's a very outdated test...

I did it to my P5 a couple of times and the car is fine...

Another guy here on the forum did it too.... His car stalled. His alternator was bad.

(so do it at your own risk... WAY easier than removing your alternator)

Your battery light will come on if the voltage goes too high.

A voltage spike could have blown your headlights.

I'm thinking your alternator is bad.
 
This morning on my way to school my p5 drove strange. At 60mph it was at 4k rpm like it didn't shift and the battery light came on. 12 hours later I start the car to go home and it starts fine, no battery light on but now my headlights are not working.

Some problem in electrical regulation, up or down, probably up to account for the blown headlight bulbs. It may be that the incorrect voltages were causing the ECU to glitch resulting in the high RPMS. As others have said, the alternator is the most likely culprit. Best to get this resolved ASAP before the odd voltages blow up something more expensive than a pair of headlight bulbs - like the radio or the ECU.
 
I just drive to Oreillys, they hook up their little machine. Presto, they tell me if my battery is bad, or my alternator.
 
Replaced the lights the day I posted this thread and had no issues but the same exact thing just happened this morning. Going to check my alternator after class
 
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Would a blown fuse cause both headlights not to work? I've had a blown fuse cause ONE headlight not to work, and I wish I had checked the fuse before I put in 2 different bulbs, only to come to find it was the fuse...replacing the front headlights can be a PITA.
 
I just drive to Oreillys, they hook up their little machine. Presto, they tell me if my battery is bad, or my alternator.

I didn't realize you could do the test without removing the alternator...
That's certainly the better option.
 
Would a blown fuse cause both headlights not to work? ...

The low beams have a separate fuse for left and right side.
Having both headlights go out at the same time can be really dangerous for the driver.

(the high beams appear to be on the same fuse though)


 
I didn't realize you could do the test without removing the alternator...
That's certainly the better option.

With a manual, it works out well. Doesn't start, then push start it. You need to plan ahead with an auto sometimes.
 
With a manual, it works out well. Doesn't start, then push start it. You need to plan ahead with an auto sometimes.

You're not even supposed to bump start our car... Apparently you can send enough unburnt gas to the pre-cat to wreck it...

 
Fuses aren't blown, relay is good. Alternator and battery both tested good. Light bulbs are toast

It sounds like you have an intermittent failure.

It would be good to get a voltage reading while the car is flickering the battery light.
I still think it's your alternator but they usually fail then stay that way.

You can get an ELM 327 code reader that will broadcast information to your phone with the torque app pro.

Or try to pullover and check your voltage right at the battery terminals while the car is being weird.
 
The car gives me the o/d off light when I cold start. No codes or anything. I don't know if it's related. When the battery light came on, once I let the car decelerate the battery light went away and it started to shift above 60mph just fine.
 
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You're not even supposed to bump start our car... Apparently you can send enough unburnt gas to the pre-cat to wreck it...


I read that. But if I am in the middle of nowhere with no choice, I will take the chance.

I have AAA though so I don't worry much.
 
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