Cager - what is the probability of two H7 pop on the same day?

[Phang]

right low beam H7 popped in the evening, replaced, found left low beam H7 popped 50 miles later (headlamp turn on) after I replaced the right side.

I continued to drive with only the right lamp as I don't have any spare bulb in the car. The right bulb didn't pop after 100 miles when I reached home.

both bulbs are non original, probably different brands replaced a year or so ago at different times.

pure coincidence?

[Triple Jim]

You can work toward an answer to that question by measuring the voltage at the headlight with the engine revved up a bit.  A failed regulator could cause high voltage and very short bulb life.

[tris]

I had exactly the same thing happen when I drove my wife's Alfa 147 a while back.

Maybe not so surprising that they sometimes fair close together given that they're both on for the same amount of time

[Phang]

You can work toward an answer to that question by measuring the voltage at the headlight with the engine revved up a bit.  A failed regulator could cause high voltage and very short bulb life.

Thanks Jim,

I just came up from the car park, voltage at the battery posts showed a steady 13.95v from idling to 3000 rpm (it's late to redline the engine now). I guess I can rule out the voltage regulator fault?

[Phang]

I had exactly the same thing happen when I drove my wife's Alfa 147 a while back.

Maybe not so surprising that they sometimes fair close together given that they're both on for the same amount of time

Thanks for the reply.

The pair are not of the same brand and not replaced at the same time, needs a lot of luck to burn out on the same day... haha

[Triple Jim]

I just came up from the car park, voltage at the battery posts showed a steady 13.95v from idling to 3000 rpm (it's late to redline the engine now). I guess I can rule out the voltage regulator fault?

I'd say so.  Unless the regulator has an intermittent problem (loose ground wire or something similar) I'd say you're into the coincidence explanation.