Both headlights (low beam) blown.

DiddyDavies

Is there any logical reason why both headlight bulbs on a car should blow at the same time?
Yesterday afternoon, I went out for a drive and as it was raining fairly hard and visibility wasn't great, I put on my headlights. Although I couldn't confirm at the time that they were both working, I checked later on my dashcam footage and they were both fine when I left my house. (obviously the camera sensor is more sensitive than my eyes).

I went to head home a couple of hours later (by this time it was twilight) and when I put my lights on, neither of the low beams were working.
I initially suspected either the switch or relay but as I had a couple of spare bulbs in the car, I tried these and found that both of the old ones had blown.
Luckily it's a fairly quick and easy job to change the bulbs, not a dockyard job like some vehicles but it just seems strange for both to fail at exactly the same time.

AdrianC

Pure coincidence. I've had it happen to me, to two bulbs that were definitely not the same age.

Quite a while back, I bought a 4.5yo car. One dip beam went out very shortly after. I changed the bulb.
A year or two later, I got in the car at night, turned the lights on... they came on, visibly brightened, went out. Both dips. Both bulbs were out. I replaced both bulbs... and both remained fine for the 5-6yrs more I owned it.

Flight3287462

Both the same age (old?), slight surge in current when one blew, who knows.  I wouldn't over think it unless it happens again.  Just work on the basis of "Sod's Law".

[Deleted User]

DiddyDavies said:

Is there any logical reason why both headlight bulbs on a car should blow at the same time?
Yesterday afternoon, I went out for a drive and as it was raining fairly hard and visibility wasn't great, I put on my headlights. Although I couldn't confirm at the time that they were both working, I checked later on my dashcam footage and they were both fine when I left my house. (obviously the camera sensor is more sensitive than my eyes).

I went to head home a couple of hours later (by this time it was twilight) and when I put my lights on, neither of the low beams were working.
I initially suspected either the switch or relay but as I had a couple of spare bulbs in the car, I tried these and found that both of the old ones had blown.
Luckily it's a fairly quick and easy job to change the bulbs, not a dockyard job like some vehicles but it just seems strange for both to fail at exactly the same time.

Happened to my once, well not exactly the same time but within an hour of each other. Both bulbs same age. 

macman

Faulty relay causes a surge and blows both bulbs?

AdrianC

macman said:

Faulty relay causes a surge and blows both bulbs?

Can you explain how?

A relay's whole job is to pass full battery voltage onto the bulbs with minimal voltage drop.