The bulb failure sensor (BFS) in our 240's is a pretty simple device - it just detects if there is a difference in the electric current draw of the Left vs. the Right circuit for certain bulbs; (Low beam headlights, brake lights, tail lights). If you put the same LED's in the Left and the Right sockets of, say, the brake lights, each will draw the same current and the BFS should be happy and not turn on the dash warning light.

So I'm a little sceptical of this Co's claim to have a "chip" that avoids triggering a bulb-out warning. A characteristic of LED's is that they require a lot less current to produce light than the original incandescent bulbs. But as long as the Left/Right balance is maintained, that reduction will not trigger the BFS.

There may be BFS's in more modern cars with fancy circuitry that detects lower than normal current - not just Left/Right balance. The ad copy's use of the phrase "Electronic bulb out warnings" suggests this. The 240 BFS is not electronic, just some wirewound coils and a reed switch. I've taken one apart, it's actually quite brilliant in its simplicity - tip of the hat to Hella, who make it.

Maybe these LED's compensate for that. Perhaps they just employ a simple shunt resistor to bring current draw back to the original level? If so, they wouldn't be the only aftermarket sellers putting a 10-cent resistor in a box and calling it a chip!
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Bob: son's 81-GL, dtr's '94-940, my 83-DL, 89-745(V8) and 98-S90. Also 77-MGB and some old motorcycles.