CAN BOTH HEADLIGHTS BURN OUT AT ONCE? - PeachParts Mercedes-Benz Forum

triacon · #1 04-01-2009, 05:04 PM

Pulled up to a store and noticed the reflection in the glass window. Both my headlights were out but the switch was on in the car. All I saw were the parking lights. Both highbeams came on and fog lights lit up as well when I pulled the switch out.

Is it possible that both lights burnt out around the same time?

Looked at the fuse box, everything looked OK there.

Is there a way to test the bulbs? Continuity test somehow, perhaps?

the car is a 1985 300 SD.

I should mention, in the past, when I would want windshield fluid to spray, I would see the highbeams light up on the car in front of me. This was not seen in the store window reflection today!

tobybul · #2 04-01-2009, 05:06 PM

sounds like you may have a short somewhere if your headlights are reacting when you activate the spray.....

tangofox007 · #3 04-01-2009, 05:14 PM

Quote:

Originally Posted by triacon

Is it possible that both lights burnt out around the same time?

That seems to be a fairly common occurence.

pawoSD · #4 04-01-2009, 05:57 PM

Quote:

Originally Posted by tangofox007

That seems to be a fairly common occurence.

I've only had one headlight burn out ever.......

triacon · #5 04-01-2009, 06:36 PM

so, do you feel they are burned out? When I purchased the car, it came with a set of euro headlights. They were placed in the trunk. Perhaps now is a good time to install them... Is it OK to use them. Will the vehicle pass inspection (NJ)? I thought someone mentioned that it may be trouble.

whunter · #6 04-01-2009, 07:00 PM

Quote:

Originally Posted by triacon

Pulled up to a store and noticed the reflection in the glass window. Both my headlights were out but the switch was on in the car. All I saw were the parking lights. Both highbeams came on and fog lights lit up as well when I pulled the switch out.

Is it possible that both lights burnt out around the same time?

Looked at the fuse box, everything looked OK there.

Is there a way to test the bulbs? Continuity test somehow, perhaps?

the car is a 1985 300 SD.

I should mention, in the past, when I would want windshield fluid to spray, I would see the highbeams light up on the car in front of me. This was not seen in the store window reflection today!

Sounds like the multi function switch is damaged.

It should be MB# 1265453124
http://www.pelicanparts.com/cgi-bin/ksearch/pel_search.cgi?SUPERCAT_FLAG=Y&make=MBZ&please_wait=N&forumid=&threadid=&command=DWsearch&description=1265453124&x=10&y=6

It is rare, but possible that both bulbs failed at the same time.

.

pawoSD · #7 04-01-2009, 08:21 PM

I think I'd check the bulbs first before I went after a new switch....

ImBroke · #8 04-01-2009, 08:58 PM

My 79 AMC Spirit did that, at least both low beams. Drove from NJ to IL in a snowstorm with high beams. That was fun.

triacon · #9 04-01-2009, 10:31 PM

How do I check the bulbs?

And what about the Euro Lights? Is it OK to use them in NJ, or any state for that matter...

What's the dif between the stock lights and the Euro Lights?

jbach36 · #10 04-02-2009, 12:33 AM

I would check the fuse first.

Second, I replaced a headlight on a trip from Atlanta to PA once. A headlight went out so I stopped in, got a bulb, replaced it. About 2 hours later, the other bulb went out. Couldn't believe they'd be timed that closely together.

jeff 1991 300d

triacon · #11 04-02-2009, 12:42 PM

I took the driverside bulb out and used a continuity test across the top 2 leads. got a beep. Perhaps that's the hibeam. then tried one of the tops to the bottom lead, nothing, other top to bottom also no sound.

will go to a local shop and test a new bulb to see which way it beeps...

whunter · #12 04-02-2009, 12:48 PM

Quote:

Originally Posted by triacon

How do I check the bulbs?

And what about the Euro Lights? Is it OK to use them in NJ, or any state for that matter...

What's the dif between the stock lights and the Euro Lights?

Un-plug a headlight, turn the lights on, use a 12V test light or volt meter on the connector terminals checking for power.

FYI: Roll the fuses in place to make better contact = break surface corrosion..

nhdoc · #13 04-02-2009, 12:49 PM

Here's what usually happens...they don't actually both burn out at the same time, it is just that you only notice they are both out because, believe it or not, driving around with one bulb it is pretty easy to overlook the fact that one has burned out...but when both are out then you DO usually notice it. Ask anyone in the repair business and they will tell you customers come in all the time saying that both headlights just burned out at the same time, but in fact they burned out one at a time and were only noticed when the second one went out. It's probably more common in states that don't have safety inspections because there isn't an annual check to find the burned out one first before #2 goes.

FYI - Mercedes fuses the two headlights separately so you would have to have 2 fuses fail for both headlights to be out, which is unlikely.

So I would say unless you are absolutely sure they both worked one day and both failed the next day I would guess you just have been driving around with one for some time and lost #2 now.

The only real explanation for a true simultaneous failure would be a bad regulator on your alternator which causes an over-voltage condition throughout the car. But you'd notice other issues too, like other bulbs would be burned out or the radio would get fried or blow a fuse.

tangofox007 · #14 04-02-2009, 02:06 PM

Quote:

Originally Posted by nhdoc

Here's what usually happens...they don't actually both burn out at the same time, it is just that you only notice they are both out....

That's it, doc. People are so inattentive that they drive around for years with only one headlight and don't realize it!!! What an absolutely brilliant theory.

My experience has been more like what jbach reports. The second light burns out shortly after the first one had been replaced. One case that I remember quite well was in the middle of nowhere in New Mexico. First lamp burned out, so I stopped at the first parts store that I came to and replaced it. Within a couple of miles, the other lamp failed, so I turned around and went back to the same parts store for another lamp. Since then, it has become my policy to replace both lamps when the first one fails.

winmutt · #15 04-02-2009, 03:38 PM

Replace the fuse.