"Don't you just pull out the old one and put the new one in JAW?
Why, yes, you do. But here are some words that the web scrapers will find that might help you.
Front incandescent indicator light fails - it's easy to tell it has failed because the flasher suddenly flashes a lot faster than normal. I was pretty sure that it was the standard wedge bulb, coloured orange, I didn't even pull it out, just went to the car shop. They can look your part up these days just by cross referencing your plate number!
For a 2014 CX9 on the drivers side, you can't really get your hand right up into the front fender to get the bulb out, that's fine, just take out the 3 bolts for the coolant reservoir, push it off to one side, untwist the bulb holder, and pull the bulb out, push the new one in.
Huh? Whaaa? It doesn't fit! Quick part check, it is a T20 Wedge bulb, 12V, 21W. Yep, that's it. Are their different base sizes for T20 Wedges? Nope, they are all the same! Am I just not pushing hard enough? Nope, I'm pretty sure if I push any harder it will smash in my hands!
What's going on?
After trying to find someone on the interwebs who has had the same problem, nope, nothing, nobody is saying anything. It doesn't make sense.
This is the time that the engineer in me kicks in. Other engineers will know what I'm talking about. You have done all the intuitive things, even maybe followed instructions, you have checked the specifications, everything seems right. So you now forget about all that, you go back to first principles, and "do whatever it takes".
Note the subtle difference in bump shape, click to zoom.
Compare with the failed one...both 12V...both 21W...the wires are on the same side. (side note - I love the simplicity of wedge bulbs. They are symmetrical, so even when there are two filaments, brake and tail, you can put them in either way, like USB C, and they work.)
It's something physical. Looking carefully at the holder and the glass base, I can see there is a slight difference in the, let's call it "locators". The new one has a "wide" bump on it, which ultimately "clicks" into the bulb holder and prevents it from rattling out. You can see if you look carefully at the photo (it's kinda hard to take a photo of glass). Because the bulb holder only accepts a narrow bump, you can't push it in.
It's on the front and back, but only on one side, the side opposite the wire. That wide bump is the only thing I can see stopping it from going in. So I could modify the bulb holder or the bulb. Clearly don't modify the holder...so armed with a little diamond file I filed down the glass wide bump to be about the same width as the original bulb.
Perfect. In it went, all was well.
So easy, so silly, I can't believe I wrote this many words about it.
"If your new T20 wedge bulb doesn't fit in the holder, compare the glass shape to the old bulb and use a small diamond file (or something that can grind glass) to reshape so it fits."
Use a jewelers diamond file to reshape it. If you don't have one, order a cheap set off the interwebs now so when you do need one, you have one.
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