Calling all electrical experts! Please help an idiot!

[Jayell]

Edumacate me, please!

I have a burned out light bulb on my bike. I can't decipher anything off the original and can't find any published specs. It looks like a 194.

Rather than go to the dealer, I matched it up at Partsource. Yep, the 194 will fit, but so will a few others. So, what's the diff?

Volts and watts, apparently. Some are rated at 12V, another 13, 13.5, and 14. As for watts, 3.5 to 5, with several choices in between.

I thought a 12V system requires a 12V bulb. No? Please explain.

I ended up with this one, a 3652. At 5W, it's the brightest. I think. My bike hasn't burst into flames yet.



And while I'm here, let me sound off on Partsource and Canadian Tire. These greedy pricks insist on selling automotive light bulbs by the pair, knowing full well the customer will only need one. The other will get tossed in a glove box or tool box and be forgotten. A few years down the road when another is needed, they get to sell you another pair! I can't complain too loudly though, because when I open my wallet and buy, I'm effectively saying "I'm okay with you boning me up the @$$". Of course, it's not the money, rather the principle.

Thanks for any help you might provide.

 

[J_F]

the volt rating will be a nominal number varying by manufacturer

no such thing as 13.5 or 14V automotive system
they're 6, 12 or 24

and the watts, yeah, brightness based on resistance

 

[Trials]

12 volts yes, but does it have a fat short wire, fat long wire, short thin wire or long thin wire, now you know how they make bulbs that take more or less power that looks like the long thin wire one, 5w won't burn your eyes out very fast.

if you put more then 13.5 volts through it, she will draw more then the 5 watt maximum rating and become a tiny fuse. poof!

 

[Trials]

Ever seen these things:
Flash bulbs light bulbs designed to blow up and release huge amounts of light for a very short time:
... whole bunch of very thin wire.

 

[Jayell]

Ever seen these things:
Flash bulbs light bulbs designed to blow up and release huge amounts of light for a very short time:
... whole bunch of very thin wire.

Wow! You're even older than I thought, Trials!

 

[GreyGhost]

Ever seen these things:
Flash bulbs light bulbs designed to blow up and release huge amounts of light for a very short time:
... whole bunch of very thin wire.

Did you search for a pic on the internet or did you just pull those out of the closet?

 

[Trials]

Once you got the light bulb figured out we go to lesson 2 : principals of the AM crystal radio
If you can follow this one you are doing great

 

[Jayell]

no such thing as 13.5 or 14V automotive system
they're 6, 12 or 24

Yep, thanks JF, that's what I always thought. 13.5 listed on the package does nothing but confuse. And I'm easy to confuse.

 

[GreyGhost]

Yep, thanks JF, that's what I always thought. 13.5 listed on the package does nothing but confuse. And I'm easy to confuse.

My guess is the marketing people are at play here with a little science to back them up.
5 watt bulb at 13.5 watts is a 4 watt bulb at 12 volts. Bigger numbers are better right?

 

[J_F]

@GreyGhost

this is something you can probably answer
not likely the average user can measure the amps to derive the watts
and I know a lit bulb will have different resistance to a cold one

you think if you use a meter with just the 9V battery pushing current
that you could measure the resistance of the 2 bulbs

and if cold resistance is the same for the OEM as the replacement
it's safe to assume same wattage?

geeking out to the n'th degree over here

 

[Brian P]

12 volts is "nominal". All nominal 12-volt automotive (motorcycle = automotive) charging systems have an actual charging voltage of 13.5 to 14.something volts because that's the voltage that a standard 6-cell lead-acid battery requires to stay charged. Bulbs will all be designed to operate at the charging-system voltage. Always. So 12 (nominal) or 13.5 (low end of normal operating range) or 14 (middle of normal operating range) all mean the same thing in practice. It makes no difference.

There are a whole bunch of wedge-base bulbs that all have the same (or compatible) shape where they plug into the socket (and those sockets are also the same) and the difference is only in the wattage and physical size. Using the wrong wattage can trip up a system that has bulb-fault monitoring. If the electrical system is "dumb" then a lower-than-rated wattage will just be dimmer. A higher-than-rated wattage can be trouble for the wiring or power circuit or heat dissipation especially if there are a bunch of them in the circuit (instrument panels often have several such bulbs). A physically large bulb might not fit the place it has to go.

I like LEDs in those applications, as long as the circuit doesn't have bulb-fault monitoring.

 

[GreyGhost]

@GreyGhost

this is something you can probably answer
not likely the average user can measure the amps to derive the watts
and I know a lit bulb will have different resistance to a cold one

you think if you use a meter with just the 9V battery pushing current
that you could measure the resistance of the 2 bulbs

and if cold resistance is the same for the OEM as the replacement
it's safe to assume same wattage?

geeking out to the n'th degree over here

You really are geeking out. Other than fancy automotive circuits that monitor every bulb so they can flash warnings on the dash, I can't think of many applications where any bulb between 3 and 5 watts wouldn't work without issue. We are only talking about 2 more watts, not 40 more watts like cheater headlights.

I think your logic holds on normal incandescent bulbs. On bulbs that strike an arc, nope. If you have a multimeter, you could measure the running current of bulb A and then bulb B to get an accurate measurement of current draw when hot. Use the same power source for both tests and the actual voltage doesn't really matter unless you really feel the need to know watts in which case you need simultaneous voltage measurement (or a constant voltage power supply). In Jayells case, bulb A is blown and unmarked so assuming it is a one off (eg, not a turn signal where you can grab the same bulb from another location) you have nothing to compare bulb B too.

 

[Trials]

Your tiny 5 watt at 13.5v lamp should measure just shy of 36.5 ohms of resistance much more or less then that and it's not likely a 5 watt bulb.

 

[nobbie48]

Your tiny 5 watt at 13.5v lamp should measure just shy of 36.5 ohms of resistance much more or less then that and it's not likely a 5 watt bulb.

That would be hot resistance. A cold incandescent bulb will be much lower. It would be easier to measure hot current than hot resistance. 5W / 13.5V = 0.37 A.

 

[nobbie48]

The brightness is subjective. If a dash light was too bright would be an annoying, possibly dangerous glare at night. For a brake light, bright is good.

There were several types of bulbs that fit the GL1500 driving lights but some would get hot enough to distort the lens.

LED's give off next to no heat but now they have to heat the traffic lights in winter to keep snow from obscuring them. A LED headlight would have the same problem. If you're riding a motorcycle in a snow storm you may not be that bright either.

 

[Trials]

That would be hot resistance. A cold incandescent bulb will be much lower. It would be easier to measure hot current than hot resistance. 5W / 13.5V = 0.37 A.

what on earth are you on about it's a light bulb not a space shuttle booster rocket seal.

 

[J_F]

he's stating the fact that as temp rises, so does resistance

 

[Trials]

can't wait to hear how he relates that to an incandescent lamps wattage rating

 

[J_F]

wattage is a calculation, it's not measured
he's suggesting it's very difficult to measure the resistance of a lit incandescent bulb
but with an ammeter, you can see the lit amps, and calculate you watts

those microscopes were mechanical, eh?

 

[Riceburner]

Replace non burned out bulbs while you are in there and save the old working ones for later.....at least that's the idea of multiple in a package.....or just marketing.