Rear Stop/Tail Bulbs

[E55BOF]

Evenin' all. I'm having trouble finding 12v 21/4W straight pin bulbs for my '98 E55's tail lights. I presume 21/5W will work OK, so long as I change both to avoid upsetting the bulb failure detector? Please advise...
E55BOF

 

[spike60]

I would expect they'd be fine, surely for the price of the bulbs you can give 'em a go.

 

[E55BOF]

It's not the cost that matters. I have an intermittent bulb failure warning light, though all bulbs are illuminating as they should. As I understand it, the bulb failure warning circuit does not monitor the wattage of the bulbs, just the resistance, so 21/5W SHOULD be OK. However....

If I simply fit 21/5W bulbs, and the warning light still comes on, I won't know whether it is the bulbs or something else in the circuit causing the problem.

From the lack of replies, I guess nobody who has read this has tried it. Oh well....

 

[andy27168]

Hi,
Having never experienced any problem getting the bulbs for my car therefore I can only presume I have the wrong wattage in mine, if your experience is anything to go by, and I have never had an issue with spurious bulb failure warning.
When you get the warning lamp up, check at which point it comes on, is it the first turn of the switch in which case it will either be front or rear side lights, second click dipped beam, then foot on the brake pedal, brake lights.
Something that threw me was that my car had 2 rear side lights each side, and what you think is the brake light (dual filament jobby) is not, its best to check with the bulb holders out of the light cluster and get someone to operate the light functions individually.
Sorry if this sounds like i,m teaching you to suck eggs, but it was,nt my intention.

 

[mersum1es]

But wattage equals resistance, when voltage is constant... (5W=28,8Ohm, 4W=36Ohm). Corroded contact and groundings of lamp units are very common...

Edit: http://www.ebay.co.uk/itm/Mercedes-...arts_Vehicles_CarParts_SM&hash=item45fd76d923
there are 'premium' brand bulbs too http://www.ebay.co.uk/itm/2x-380-P2...ts=Car+Make:Mercedes-Benz&hash=item19dc9a933e

 

[E55BOF]

Thank you gentlemen; I did actually know most of that, but no offence taken.

The bottom, dual-filament, bulb on the RHS blew a filament, so I replaced it with a (21/4W) bulb I happened to have in the garage, but the bulb failure warning comes up on switching on the side lights, and intermittently on braking. I put it down to the resistance of the new bulb, which is noticeably brighter particularly on side lights, being different to that of the old bulb in the same position on the LHS.

Still no definitive answer to the original question. Oh well...... I'll try Spike's suggestion and give it a go.