7225 Rear fog bulb

We had a customer come in yesterday with a 2008 997.1 Carrera that had a rear fog lamp out. Nothing I could find online showed what bulb it took, so we removed it and I read 7225 on the original Osram. The only thing we could get in short time was a Sylvania LL.

I can get a Philips 7225 from my supplier but it doesn't state if it is LL or not. What would the best non-LED bulb be for this application?

Mr. Merk said:

We had a customer come in yesterday with a 2008 997.1 Carrera that had a rear fog lamp out. Nothing I could find online showed what bulb it took, so we removed it and I read 7225 on the original Osram. The only thing we could get in short time was a Sylvania LL.

I can get a Philips 7225 from my supplier but it doesn't state if it is LL or not. What would the best non-LED bulb be for this application?

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Rear fog lamps are so infrequently used that perhaps regular inspection of the bulb for pearlization is all that is needed. It looks like a 3496 will also fit the bill, but will potentially make that rear fog lamp too intense.

Rear fog lamps are NOT a fashion toy; advise your customer that they must be used correctly or they will present a hazard for other drivers (and by extension, themselves). I bring this up because it seems unlikely that a rear fog lamp bulb is burned out already considering the potential infrequency of use.

I don't think he'd ever even used it. Maybe the previous owner mistakenly used it all the time like I see so many do.

I just don't want to install crap LL bulbs in my clients' vehicles if I can help it.

Mr. Merk said:

I don't think he'd ever even used it. Maybe the previous owner mistakenly used it all the time like I see so many do.

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I see that with Audis that have rear fog lamps. Do the drivers think it looks cool? Does it not have an interlock to require manual reactivation?

I just don't want to install crap LL bulbs in my clients' vehicles if I can help it.

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Generally, long life bulbs are a bad idea in exterior lighting. But such an infrequently-used lamp may never see the filament degradation and envelope blackening that afflict other light positions.

Also, usually replace bulbs in pairs, but if the other lamp just doesn't light/isn't wired in the fog position, and if the minor filament isn't used, then you can replace them as singles (so the 2-pack is basically the one you need+spare). If the minor filament comes on with the parking lights/headlamps, then of course replace them as a pair because the minor filaments differ slightly between a 3496 and 7225 and will be noticeable.

I was at Mercedes-Benz for four years and a lot of people unintentionally drive around with the rear fog lamp on. They just think they're turning on all the forward lights they can when driving. They'd come in saying they were told they had a tail lamp out, so I would inform them on how and when to use the rear fog lamp.

The Porsche in question only has a driver side rear fog, so I kept the other as a spare.

Same with Mercedes, at least the older ones, one (driver) side only.

(Wonder how single side relates to intensity concern)?

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7225 is Osram's item number for a P21/4W bulb. You might have better luck searching for P21/4W rather than 7225. No other type of bulb will fit, aside from a P21/4W (if this were a P21/5W, then an upgrade with 3496 would be possible...but not with P21/4W, which has a BAZ15d base not compatible with the BAY15d base of P21/5W, 3496, 1157, and several others).

In tail light applications like this, a long-life bulb can be advantageous; this isn't the same deal as with headlight bulbs where LL means poorer performance. The only thing you have to watch out for, as Alaric says, is that sometimes LL bulbs last long enough to blacken significantly -- then they should be replaced even if they still light up.

Alaric is also right that they should be replaced in pairs, not only to assure equal light output from both sides, but also to avoid false-triggering the vehicle's bulb outage detection circuit.

-Virgil- said:

7225 is Osram's item number for a P21/4W bulb. You might have better luck searching for P21/4W rather than 7225. No other type of bulb will fit, aside from a P21/4W (if this were a P21/5W, then an upgrade with 3496 would be possible...but not with P21/4W, which has a BAZ15d base not compatible with the BAY15d base of P21/5W, 3496, 1157, and several others).

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D'oh! Of *course* I missed that distinction on the base-- for those wondering, the BAY15d base has the index pins with a 180˚ cylindric offset; the BAZ15d base has a cylindric offset of 190/170˚, which prevents fitment since the slots on the socket don't line up. (Unless'n you cram it in real good!!!). I was fixated on the light center length and base diameter and forgot about the index pin offset.

Is it possible that someone heisted the bulb out of the rear fog to replace a burned out brake/tail at some point? It looks like they take the same bulb, and would explain the reason for a burned out/blackened bulb in the fog position (presuming said bulb pilferer put the dead bulb from the other position into the fog) without using it improperly.

-TC

My 2002 Highlander, with 151,000 miles on it still has the FRONT factory fog bulbs in it that were installed in the factory in Japan when built!

Lark Hunter said:

Is it possible that someone heisted the bulb out of the rear fog to replace a burned out brake/tail at some point?

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No.

The same thing that stops a BAY15d bulb from fitting in a socket for a BAZ15d socket prevents the BAZ15d bulb fitting a BAY15d socket.

Qship1996 said:

My 2002 Highlander, with 151,000 miles on it still has the FRONT factory fog bulbs in it that were installed in the factory in Japan when built!

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Sounds like you use front fog lamps appropriately (that is, extremely rarely).

Alaric Darconville said:

No.

The same thing that stops a BAY15d bulb from fitting in a socket for a BAZ15d socket prevents the BAZ15d bulb fitting a BAY15d socket.

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Gotcha. My resources listed the tail/brake position on the car in question using a P21/4W bulb as well, as opposed to a P21/5W with the more common 180 degree pin offset.

-TC

I ended up purchasing a pair of Osram 7225 bulbs from our supplier to keep in stock. We will probably never need them again!