I have a burned out blue resistor in my ECU that is labeled 3R9J. Now I did a search and found that this is a 3.9 OHM resistor. I can't find anything that small in my area at all!! The lowest that Radio Shack carries is 10 ohm. Now dumb quesion here..... What if I used a 10 ohm resistor instead of the 3.9? I warned you, dumb *** question I know!

 

Without knowing exactly what circuit it is in, basically whatever it is going to will see a lower voltage than it normally would, which is bad.

 

Everybody thank Hailers for providing this link for us a while back

www.mouser.com/koa

 

Sweet! Good link!

Ok, so how big of a voltage difference would it really be comparing a 3.9ohm resisoer to a 10ohm resistor? Lets pretend that 12v is going through, or even 6v just so I can see the difference. C'mon electrical gurus!

 

All else being equal (which it won't be), the 3.9 ohm guy will allow a 3.1 amp flow at 12v, and the 10 ohm will allow 1.2A...That's if I remember the formula correctly, lol...It's been 20 years since this crap was inputed into my one brain cell

 

http://www.grc.nasa.gov/WWW/K-12/Sam...w/ohmslaw.html

http://www.angelfire.com/pa/baconbacon/page2.html

 

Ahh, that's sweet, you provided the formulas for me

I guessed right the first time, using I=E/R (E is voltage, not V, lol) from memory...Not bad, eh???

 

i thot voltage was v, as in V=IR... isn't E a constant?

 

Actually, I don't know why its symbol is "E", all I know is that symbol is what was shoved into my neurons all those years ago, lol...

Maybe Hailers can provide us with a link that explains why it's "E"

 

Now that's what I'm talking about!!!! Thank you very much!! I love learning something new

 

Some people represent voltage as V, and some as E, Im not sure if there really is a difference, Ive seen it represented both ways, even in textbooks.

 

Ok, so this place by me has some 3.9 OHM resistors but now I need to know the wattage I need. I know this is tough since I don't know what circuit it is on. The blue resistor says 3R9J and has a 1W on it...would this be the watts I need or would it be 1/4 or 1/2 watt? Sorry for these questions but I am at work and was going to head over to the place since they close shortly after I get off.

I looked at the site that Hailers gave a while back but I can't seem to find an area that gives a definative wattage.

 

I haven't had to play with this guy yet, but I can tell you you're not the first to have problems with that particular resistor, it wasn't but about a month ago someone else ran into the same problems. Do a quick search using that resistor number, figure out who wrote the thread I'm thinking about, and either PM him, or see if you can get the answers off of the thread....

 

E for energy?

 

How about "E" for electron-volt???

Einstein's formula does not apply to ohm's law, lol...

 

That's just sad of me....I didn't even think to search by 3R9J!!! HAHA! Thank you very much for kick starting my head ;p

Well, going by some other older threads, Icemark mentioned and some other mentioned that it is a 1w resister around 3.9 ohms. When I measured some of them installed on the board last night, I got around 4.2 omhs or so. I guess if i get close, them I'm all good! I'll let you all know if it works and what it was hooked up to.

 

Your meter might not have been accurately zeroed, or you're reading your leads' resistance also. Stick with the 3.9, with the same tolerance accuracies (and wattage) of the original, and you'll be fine...

 

Well got the resistor! I put it in and I'm good. It was the resistor that is hooked up to 2K if anyone knows what this does. Thanks for all the help!!

 

The infamous split-air solenoid valve. Likes to blow resistors and melt wiring

 

I think you respond faster than I can post the question.

The evil split air resistor eh? Would it have any effect on performance?

 

Only if you're performing for the emissions inspector