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Philips H1 Auto Bulb Corrosion Problem – Mercedes E Class W210 Fog Lamps


No under bumper lamps and the dashboard bulb failiure indicator pointed to the fact there was an issue with the fog lamp bulbs on the E Class W210.  When the weather improved enough to investigate I had a peek at the problem.  As you may know, access to the lower fog lamps rear casing is very restricted without raising the car on a jack, this was the reason I had not tackled the problem until it had at least stopped snowing!

Mercedes W210 E Class H1 Bulb Problem

Both lamps had failed, but not blown filaments!

A small hinge-down flap, forward of the front wheels in the plastic under-skirt  is undone by slotting a 50p coin into and rotating the catches (two on each flap), once open this gives access to the rear of the fog lamps.  The lamp housing is opened by releasing the single plastic catch at the bottom of the assembly and levering the rear lid outwards then down – out of two locating slots on its top edge.  There is a standard spring-arm retainer holding the H1 lamp in place, once released the bulb can be withdrawn and the single spade electrical connector removed.  Replacement is a reversal of the removal.

Philips H1 auto bulb corrosion

The bulb itself was in perfect condition, but the welded connection between the filament and holder body had corroded causing an open circuit.

On removal and inspection the interesting thing that I noticed was the bulbs themselves had not ‘blown’ their filaments, but had corroded in an identified weak spot on the filament connection where it joins to the fabricated steel holder. The fact that this was common to both left and right lamps with the same corrosion, pointed towards a possible issue with the termination welds on Philips H1 type bulbs.  If you look at the photograph below you will see a yellow sulfurous corrosion that has eaten through and separated the spot weld that attaches the filament wire to the metal support (earth) body of the H1 lamp.  When it was cleaned away with a sharp pointed knife it could be seen that the corrosion had totally separated the once welded filament wire from the support post creating an open circuit.

Philips H1 auto bulb corrosion close-up

Corrosion had allowed the filament tail spot-weld to part from the lamp holder body.

As this had happened in an identical way on both bulbs I suspect a manufacturing fault or a selection of dissimilar metals that have some galvanic action causing this corrosion.  Either way it was the failiure of the lamp bulb construction rather than the filament that caused the open circuit in both cases.  I replaced my lamps with Osram H1 bulbs which have a better more robust filament connection arrangement and will now use this manufacturer in preference to Philips !  Make your own mind up !

Osram automotive bulb data : Osram data sheet link.

Philips Auto-bulb corrosion problem

Corrosion has caused the separation of the terminal and filament.

Mercedes Vito LED Side Light Upgrade

I recently ordered on-line, a number of T10 LED ultra-bright white side light bulbs for the Vito. After some web research of what offered the best and most uniform light output I settled for the 20 LED cluster type. These were ordered from Hong Kong for very little cost and to be honest when I eventually got hold of them I was surprised at how well made they were. The performance of these lamps was exceptional, with uniform, high brightness illumination even in daylight. I fitted the remainder of the ordered quantity to my wife’s Nissan Micra and friends Mitsibishi L200 and everyone was very pleased with the outcome. Exchanging my standard headlamp bulbs with Osram Night Breaker Plus, transformed the performance of the lighting measurably.

Here are the LED side light bulbs.

T10 LED Side Light Bulbs

Once fitted to the headlamp assembly the light given is very white in comparison to that of the normal tungsten T10 side light bulbs.  One thing to remember is that these LED bulbs are electrically polarised – If once fitted they do not illuminate, take them from the holder and turn them round re-inserting the blades of the lamp in the opposing way.  Due to this it is important that you test the lamps for correct illumination before inserting them into the reflector and building up the rear of the headlight casing.  You will need to make sure the LED lamps that you order are compatible with bulb-failiure warning systems (These have a resistor within them that presents the same drawn current to the electical sense circuit as tungsten lamps) or the vehicle bulb failiure warning light in the instrument panel will illuminate incorrectly.

Here is the sidelight shown illuminated in daylight.

LED Side Lamp