# Anyone here tried a 35w GY6.35 style halogen bulb for reverse lights (921 bulb)?



## absolutt (Aug 10, 2007)

Obviously the main bulb draw these days is to use LED's, so there's a huge market for them, all kinds of costs, CANBUS support, etc. I ran across a really terrific posting about the 921 light bulb typically used for reverse light applications, over on the Tacoma World forum. The OP studied 7 different bulbs, from incandescent to LED. Results were pretty astonishing. Now, for most people a workable LED (no CANBUS error) will be better than the original incandescent 921, as long as it's at least 500 lumens. But... why stop there?

The "winner" of the shoot-out was the Osram 35w GY6.35 bulb. It wasn't originally meant as an automotive bulb, but it works. At least the folks on that forum (and on Amazon reviews) state they've installed it with success. Extremely bright. Given the limited run time (only on when going in reverse), and relatively cheap cost ($6 per bulb) it seems to be the logical choice. I'm wondering if anyone here has installed such a bulb on their VW/Audi.

My only concern with this, is the fact that the bulb is 35W and would most likely generate a lot of heat. Considerably more than the original 921 incandescent bulb. Now, it may not be an issue due to the short bursts of runtime, but OTOH I wonder if it's something that may be "inconspicuously" damaging. Meaning, that the heat generated may not be enough to notice anything wrong up-front, but I wonder if repeated use over time may start to cause deformity to the plastic bulb socket housing. I know from personal experience that this is possible to happen, under the right circumstances. My Audi A3 had a license plate bulb fault at about 5 years into ownership, which was due to the bulb socket mounts melting. The engineer who designed the license plate light & latch button assembly didn't properly incorporate venting, so the heat buildup eventually compromised it. So... it's possible to happen (I replaced with LED's about 6 years ago and it has been fine since).


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## BsickPassat (May 10, 2010)

I've had 35W reverse bulbs in my old MKIV without issues.


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## absolutt (Aug 10, 2007)

BsickPassat said:


> I've had 35W reverse bulbs in my old MKIV without issues.


Thanks -- good to know. These seem like the way to go, as they're brighter than most LED's while costing a good bit less. No real issue with efficiency since they're only used momentarily.


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## zibercat (Aug 20, 2019)

*912/921*

I been trying to change all my bulbs to LED, I tried the Lasfit LED Canbus 1157 (BAY15D @$19.99 set), 194/168/T10 6W6 ($11.99 set) and the 912/921 T15 W16W ($13.99 set) only the 912/921 worked w/o any errors. Then I tried superbrightleds 1157 and the 194 both canbus, only the 194 worked w/o error (my 2018 Jetta uses 4) $2.95ea.


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## absolutt (Aug 10, 2007)

zibercat said:


> I been trying to change all my bulbs to LED, I tried the Lasfit LED Canbus 1157 (BAY15D @$19.99 set), 194/168/T10 6W6 ($11.99 set) and the 912/921 T15 W16W ($13.99 set) only the 912/921 worked w/o any errors. Then I tried superbrightleds 1157 and the 194 both canbus, only the 194 worked w/o error (my 2018 Jetta uses 4) $2.95ea.


LED's can be hit/miss depending upon the model -- might work in a VW Jetta but then fail in an Audi A3. The culprit might be different versions of VAG COM, where one is more aggressive than the other on detection of current draw.

I'd been tempted to go with a facelift LED tail lighting system, but all told it's over $400 USD for the conversion. Not really worth it for me, given my ownership is nearing the tail end (12 years!). However, one thing I do appreciate is LED rear signals so I decided to give one kind of bulb a try. There are many choices out there, a good portion claiming CANBUS error free. But there are a number of different designs and costs. AUXITO has been given a thumbs up by some VW & Audi owners. I got a set of their P21W / 1156 / 7506 bulbs -- IMAGE. Won auction for $10 shipped (pair). They worked fine as rear turn signals, but threw a bulb-out for tail / brake light bulbs.

The key thing about the LED is not just avoiding a CANBUS bulb out error, but also providing sufficient emitter brightness in multiple directions. This particular bulb I got seems to leverage the non-LED bulb chamber well. Turns signal brightness seems to be a little more than incandescent. That's exactly what I was looking for. You don't want the LED bulb array to be too bright and distract / annoy drivers behind you.


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## absolutt (Aug 10, 2007)

I picked up a pair of these bulbs, but they didn't fit very snug. I had to change the shape of the prongs in order to get a solid fit. I found this shape worked well:










You have to be careful bending the metal. 2 thin pliers is necessary, so you prevent any bending stress on the glass. Brightness is well more than double the original bulbs. Just to validate the heat level, I let the bulbs stay on for a full minute. Touching the housing & lens revealed no appreciable heat build-up. So no worries about them being too hot & risking any plastic melting. This is so well worth it. Not only cheaper than LED's, you don't have to waste time taking chances with possible CANBUS errors.


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