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View Full Version : Both headlamps died, where to start?


terra_firma
02-06-2014, 01:29 AM
I've been driving around with my hi-beams on cause i've been dreading whatever electrical issues are in store for me. Both headlamps went out at the same time. Are they separately on fuse 2 and fuse 3? i took the fuses out and looked at them - they look good, assuming they are the right fuses.

Aqua Puttana
02-06-2014, 01:58 AM
Have you checked the lamps??

I have seen where both sides go at the same time. My guess as to that "coincidental" failure is that, depending upon the failure mode, when one lamp burns out it may spike the system voltage enough that the other similar age lamp gets stressed and fails at the same time. I'm not sayin' that's what happened, but I would first check both lamps. vic

surlyoldbill
02-06-2014, 02:06 AM
I've also experienced them both failing about the same time, as have many others. Just get a good replacement pair (please don't get the stupid blue color ones).

halexh
02-06-2014, 09:19 AM
Have you checked the lamps??

I have seen where both sides go at the same time. My guess as to that "coincidental" failure is that, depending upon the failure mode, when one lamp burns out it may spike the system voltage enough that the other similar age lamp gets stressed and fails at the same time. I'm not sayin' that's what happened, but I would first check both lamps. vic

Also I can't remember if it was posted on this forum or somewhere else. But it was explained that the factory tolerances/specs are so stringent that usually if one bulb goes the other will soon follow if they were replaced as a pair. This combined with the theory that there is a voltage spike makes a lot of sense.

Also I believe almost every function of each headlamp has a fuse for L and fuse for R. Both fuses going out would indicate a bigger problem.

flman
02-06-2014, 10:21 AM
I have also seen the other go out not too much longer then the first on my T1N as well.

pgr
02-06-2014, 01:29 PM
The same on my '04! Since I replaced the plastic bulb holders with porcelain holders and disconnected the DRLs they last forever.

david_42
02-06-2014, 03:51 PM
It's worth while getting an inexpensive multi-meter, so you can check fuse and bulb resistances. On a happy note, Sprinter headlight bulbs are no longer the most expensive blubs at Napa Auto. Some of the hi-intensity bulbs run over $100.

My right-hand low beam has gone out 3 times, all the others are OEM. YMMV

terra_firma
02-09-2014, 02:02 PM
Hey guys. As of right now it seems like two new bulbs were the answer! So looks like we have a pretty consistant theory.

david_42
02-09-2014, 02:44 PM
Hey guys. As of right now it seems like two new bulbs were the answer! So looks like we have a pretty consistant theory.

I must admit, I've wondered why my experience has been different from just about everyone else's.

Aqua Puttana
02-09-2014, 04:50 PM
I must admit, I've wondered why my experience has been different from just about everyone else's.
My theory is that for a period of time the MB supply of OEM lamps was sub-standard. Where's BEVO when you really need it?? :rolleyes:

When I first started hanging on this forum lamp burnout seemed like the hot topic. I stocked up on 55w headlamps at a cheap price from J.C. Whitney. I think that I've used one, maybe two so far over 6 years of operation. I certainly haven't seen an epidemic.
(Knock, touch wood. They'll probably all blow tomorrow now. :bash: )
Lamp burnout no longer is the hot topic around here either.

2 lamps at once...

I believe that much depends upon the failure mode of the lamp and the state of the electrical system at the time of failure. If the filament just parts open then there may be a bit of a voltage spike, but probably not too much. If the filament parts and somehow a short piece falls against the power post(s) then that lower resistance load can create a dip in voltage which the regulator sees and increases the alternator output to compensate. The short piece then quickly burns off which removes the load while the alternator has been ramped up. That would cause a higher spike which might take out the other lamp.

Or it may all be coincidental and I'm just full of B.S. I have no data.

vic