LR3 brake light question

[Carson G]

IIRC my upper bulbs are just regular old 1157’s. I can’t remember if the bottoms are the same or not.

 

[2.ooohhh]

Manual lists P21/5W as the correct bulb. Eric, which did you get?



What's special about the european bulbs?

Europe has additional standards that bulbs have to meet, one being nickel plated bases. They began doing this in the late ‘70s at several manufacturers request. It reduces corrosion at the bulb socket, as well as standardizing resistance allowing those keen little warnings BMW (for an example of one manufacturer) that let you know a light is out.


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[Red90]

Manual lists P21/5W as the correct bulb. Eric, which did you get?



What's special about the european bulbs?

In the US, the common bulb is the 1157. It is physically the same but the wattage is a bit different to the P21/5W. This can be enough to piss off the computer. A burnt out bulb does silly things as well.

The brake switches are also known to leak between the light switch and the switch for the computers and this also causes all sorts of weird events.

 

[2.ooohhh]

This is a Phillips 21/5w

It’s what you’re looking for. Winzer carries them and supplies shops around here, or I’ve had decent luck ordering them from rock auto.

They are made by the same companies, the euro bulbs are typically produced in Germany, France, or Hungary where as your local autozone/Walmart fodder will often be Mexico or China in origin though I have seen some upmarket stores carrying “long life bulbs” marked up at a premium with nickel bases.


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[Eric K]

so maybe it's the bulb. I have a 7528 (which is what the part store catalog says I need for my car), however it says it's compatible with 1034, which at least seems the same format as 1157, but it is decidedly not 1157. Strange the parts catalog is that wrong.

 

[Blaise]

Great news!

 

[Red90]

Just for fun, I checked wattage of an 1157 and a P21/5 using a 300W regulated 12V supply. Physically, they are identical. Same filament orientation and location. All measurements after the amperage stabilized (amperage drops as the filaments heat).

The P21/5 was a Lucas branded bulb, part LLB380
4.8 W and 18.0 W @ 12V.

The 1157 did not have a brand. Made in Hungary.
6.2 W and 19.7 W @ 12V.

 

[Red90]

I’ve used regular old auto parts store bulbs for the last 7 or 8 years my truck doesn’t care. I haven’t had to change them Since I put them in. No faults they’ve worked just fine. My harnesses were another story they started going around 90k and were junk by 100k.

On a trip last year a friend in a D3 would randomly lose his special programs, usually right at the hardest obstacles and would need to reboot the car. After the trip, he installed Lucas P21/5 bulbs and the fault has not re-occurred.