Electrical help needed to figure out bulbs needed

[scot850]

I have added a link to my original request for help to try to figure out alternate sources for dashboard item bulbs:

viewtopic.php?t=107902

I thought I was making some progress by ordering some bulbs from AliExpress. Turns out to be a bit of a bust, possibly.

I was trying to work out what the wattage of the bulbs needed to be, but with bulbs potentially specified from 12V or 14V that already sets an obstacle to figuring this out. I had thought if I could figure out the resistance of the bulbs using my circuit tester, then as shown by someone in my original post. They pointed out (and reminded me) that the simple calculation of:

Watts (W) = Voltage x Voltage (voltage squared)
------------------------------------------------
Resistance (Ohms)

There is something wrong either with both my circuit testers or the way I am trying to calculate the Watts. When I do a resistance check across the T4 bulb leads I get around 10 Ohms on the OE bulbs, with some lower and others higher around 35-40 ohms.

Assuming I use 12V, even with the highest value that would convert to 3.6 W

One of the bulbs I bought was listed as for Honda and other brand bulbs and listed as 12V and 1.4W. When I do a resistance test I get a huge variation of 16 ohms to 40 ohms. So there is now math working here. So what am I not taking into account?

The quality of the bulbs I bought from Ali Express were (not surprisingly) terrible with variations from 16 ohms to 40 ohs with maybe 40% in the 18 ohm range, 40% in the 33 ohm range and the rest from 16 to 40 ohms. So basically junk.

So what am I doing wrong here?

Thanks,

Neil.

[abscate]

I think Ali Express is expressly ailing you …thst huge variation in resistances is telling you the parts are poorly made

[volvolugnut]

Years ago I bought some 12V LED bulbs for a flashing sign that operates 24/7. They lasted a few months which was about the life of normal bulbs. Then I bought some name brand bulbs (sorry I don't remember brand) and they are still working.
volvolugnut

[scot850]

I am not intending fitting LED bulbs to the interior although I know there are companies out there that sell them for Volvos and other brands. I like you tend to leave these things mostly well alone as taking the dash apart to swap out bulbs is not something I want to do on a regular basis.

We had those old brass fitting lights over our bathroom sinks in our old house. When a bulb failed I thought going LED would be the way to go to cut down on the 6 bulbs/unit (so 12 bulbs) with 60W/bulb output to comparable 12W LED's for light output. Those 12 bulbs all failed within a year with the first failing in less than a month. I wrote to the manufacturer's complaining and they sent me a whole replacement set. They did not last any longer so I swapped back in the original 20+ year old incandescent bulbs.

I have been talking to a supplier of headlight LED bulbs with an anti-flicker unit that have lifetime warranties and supposedly 5 x the brightness and a claimed propriety anti-dazzle design. Pricey at about $300/pair CDN. Hella also sell LED headlight H11 bulbs for around $150 CDN + shipping for a pair with the add-on anti-flicker tech. I'll link that on my LED headlight thread later.

Neil.

[scot850]

So, kind of going off topic here. What I was hoping for is some idea how to figure out what bulbs to look for spec wise 12V or 14V, 1-1.4W or what is actually needed and how to figure this out as the bulbs do not seem to work with the theory unless I am doing something wrong in measuring or math'ing here.

Neil.