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Our Crosstrek has a habit of blowing both headlights and occasionally taillights at the same time. Everything is working fine and you start it and the lights are out.
I suspect that the problem is the act of starting the car. Is there a diode associated with the solenoid? I have worked with other systems where there was a diode reversed on a solenoid to absorb the back current associated with opening a switch on a motor or coil and the collapse of the magnetic field produced a surge. If the diode failed, the surge was fed back into the system causing damage. Blown lights on start up would match that issue.
Has anyone seen this?
 

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2021 Crosstrek Limited
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When the car is started the voltage drops to around 10 volts. Turn the lights off before turning the engine off.
 
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When the car is started the voltage drops to around 10 volts. Turn the lights off before turning the engine off.
TL;DR Yep - Flickering power is really stressful on filament bulbs.

Bulbs typically break in the first few seconds of usage because the initial current that flows after the bulb is switched on when it is still cold. The resistance of a filament light bulb increases as the potential difference applied rises. The inrush current can spike as much as 10 times the magnitude of normal operating currents. This large current creates a high magnetic field in the filament coil leading to mechanical stress as well as thermal stress, causing filament failure. Imagine your car doing that 10 times every start.
 

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TL;DR Yep - Flickering power is really stressful on filament bulbs.

Bulbs typically break in the first few seconds of usage because the initial current that flows after the bulb is switched on when it is still cold. The resistance of a filament light bulb increases as the potential difference applied rises. The inrush current can spike as much as 10 times the magnitude of normal operating currents. This large current creates a high magnetic field in the filament coil leading to mechanical stress as well as thermal stress, causing filament failure. Imagine your car doing that 10 times every start.
that's right but you shouldn't have to turn off your lights before starting your car
 

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that's right but you shouldn't have to turn off your lights before starting your car
Yeah I agree. It's not a normal thing. My X-trek is 3.5 yrs and never replaced a burned out bulb.
Check your voltage regulator:
If that's good, it something environmental, like lots of starts, or you live on a bumpy road that damages the filaments.
You can mitigate the headlights by switching to LED bulbs. Here in Canada we have road legal LEDs (example). They are OEM brightness and designed to use a halogen housing. The reason most LED headlight bulbs are awful is because they are as bright as a quantum singularity and don't have a beam cut-off built into the bulb that actually works.
 

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Why on earth would you want to have your lights on when starting the car? All it does is load the battery and take power away from the prime task of starting and running the car. Turning them on 10 seconds later doesnt seem onerous.
 

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Why on earth would you want to have your lights on when starting the car? All it does is load the battery and take power away from the prime task of starting and running the car. Turning them on 10 seconds later doesnt seem onerous.
Our Limited has keyless entry and push to start and the headlights are on auto, so there are very few steps to getting in and going. I'm guessing the lights come on at the same time the engine is starting if it's dark. They're also LED and no problems in over four years.
 

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So? Technically flashings your lights (in the case of letting someone out etc..) is very detromental to bulb longevity??
 

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So? Technically flashings your lights (in the case of letting someone out etc..) is very detromental to bulb longevity??
Yeah, I would imagine so but not for LEDs.
 
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