Very small resistor

Can any one identify this R9 it is so small I cant even tell how many bands there are! It is in the rear taillight module

I would say the same as R4.

Looks like red black black gold…which is 20 ohms, 5% tolerance. It’s a quarter watt size. So with 12V across it, were that to occur, dissipated power would be 144/20 or about 7W.

I mention that because it looks like it’s fried. As such, the two apparently black bands might be charred paint rather than actual black–notice that the gold didn’t do very well. I’d certainly check the 1N4004 diode at right, and the zener at left…either might have failed and caused the R to overheat. IMHO.

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It seems to be a common failure; many posts on jaguarforums. Red-Red-Black-Gold = 22R 5%.

Ron

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We were writing at the same time. Could be. But R4 is 2200 ohms…with a maximum of 15V across it, power would be 225/2200 or about 1/10 watt. No circuit failure with a nominal 12V supply could fry it.

Wow! This is real-time problem solving!!

I may be a mediocre mechanic, but after 43 years in the electronics business, I learned a few things about electrical troubleshooting.

Agreed that finding a photo of the circuit on line is a good troubleshooting method, but I’ve been at it for much longer than 43 years, and most of that time I had to figure it out myself. :slight_smile:

BTW, in the photo of the charred resistor, it’s hard to imagine that one black band started as red, yet looks identical to the other band that started as black. I suspect that either 20 (black black) or 22 (black red) ohms would work fine in that circuit, though.

Layman’s pov here, :stuck_out_tongue_winking_eye: take a look at the photos again, the pic provided by @Ron_Knipper shows the correct (identical) resistor but fitted in the circuit “upside down” - and even I know that makes no difference with a resistor!!

C4 doesn’t look like it’s been having a good day either.

Obviously, but my point had nothing to do with that.

There are two black bands on the fried resistor. Based on the photo posted later, one of them was originally red, and the other was originally black. I found it strange that “charred red” and “charred black” looked exactly the same. If one were very careful, they might consider that the charred resistor actually had originally two black bands–despite the example of another circuit board that says otherwise. Supporting this argument, there is another red band, and a gold one, whose colors survived. But, weakening the argument, those two bands are near the ends, where they might have received some heatsinking from the copper wires.

I went on to point out that in this case, luckily, that worry is moot–20 and 22 are close enough to each other so that it wouldn’t matter. Sorry for pedantry and IMHO as always. :slight_smile:

Good point about C4, Andrew!

Thanks for the link to a good board! With that info I was able to find a local electrnoics repair shop to take on the project, even thouhg I am good with a soldering iron they can replace the zenodes and diode without me having to find someplce to buy 2 resistors etc.