Weird Resistor Identification

[Nath 1,975]

Hey guys,

 

Got a bit of a problem - one of the resistors (at least I think it's a resistor...) on my temp gauge seems to have blown (was loose on the board and had black all around it). Hit it with a multimeter and it didn't come up with anything.

 

Problem is I've never seen something like this before, it has no colour bands, only letters and numbers. I've tried looking up ID charts on google but nothing seems to come up that matches what I'm after. Checked with a couple of people who are good with electronics, and they weren't sure either.

 

Anyone have any ideas?

 

First Line -  R S 2 P

Second Line - 6 8 Ohms sign J

 

[SPArKy_Dave 8,892]

It's an RS Series 2watt Metal Oxide Resistor,

(metal oxide resistors, are basically high quality resistors designed for use in demanding situations - like automotive parts.)

 

RS = RS series Resistor

2P = 2 Watt Power Rating

68^ = 68Ohms

J = +/- 5% tolerance rating

 

http://www.token.com.tw/pdf/resistor/metal-oxide-resistor.pdf

[SPArKy_Dave 8,892]

It could also be a FUSIBLE resistor, designed to protect the gauge itself.

 

If it's gone open circuit, without any obvious signs of destruction,

I would assume that it IS a fusible resistor.

[Ando81 2,949]

I was going to suggest taking it to JAYCAR and letting a electronics nerd work it out for you but forgot that Sparky Dave is the man to talk to when it comes to power! Great job bloke

[Nath 1,975]

It's an RS Series 2watt Metal Oxide Resistor,

(metal oxide resistors, are basically high quality resistors designed for use in demanding situations - like automotive parts.)

 

RS = RS series Resistor

2P = 2 Watt Power Rating

68^ = 68Ohms

J = +/- 5% tolerance rating

 

http://www.token.com.tw/pdf/resistor/metal-oxide-resistor.pdf

 

 

 

It was loose on the board (moving around in its solder) and there was a big black patch around it. It wasn't giving me a reading on the multimeter.

 

Do Jaycar sell stuff like this? That was going to be my next stop.

 

On my old temp gauge there's another resistor (banded though, looks normal) sort of like it, if the bands match the letters would I be good to swap them out, or should I replace it with the exact same thing I took off (can't be that good if it blew...)

 

Alternatively I have to go hunting a new one.

[Crazy2287 1,886]

Should just be able to replace it with a 2watt or greater resister of the same value. J-car may or may not have 2W ones of that value in stock as its a pretty heavy power rating but they may have a higher wattage in ceramic. or just place an order in, Check their catalog. http://www.jaycar.com.au/

 

Resistors rarely fail for no reason, are you sure it's not caused by a problem elseware?

 

By "not giving you a reading" is it open circuit? or a short? It dose not look like it's cooked itself does it smell funny? like cooked electronics? Could have simply failed due to cracked solder joints.

[Nath 1,975]

Should just be able to replace it with a 2watt or greater resister of the same value. J-car may or may not have 2W ones of that value in stock as its a pretty heavy power rating but they may have a higher wattage in ceramic. or just place an order in, Check their catalog. http://www.jaycar.com.au/

 

Resistors rarely fail for no reason, are you sure it's not caused by a problem elseware?

 

By "not giving you a reading" is it open circuit? or a short? It dose not look like it's cooked itself does it smell funny? like cooked electronics? Could have simply failed due to cracked solder joints.

Can't really see to well in this photo because of the light but it's definately blackened around the board where the resistor is. The soldier looks like it did crack as well.

 

I put the multimeter directly on the resistor on either side of the prongs and it said it wasn't giving any resistance at all.

 

Picked this one up from Jaycar - 5Watt 68 ohm. Hopefully there's enough room for it to fit. They only had 1W and 5W.

 

 

 

No idea if it was caused by something elsewhere - This dash board didn't come from my car, and all the other gauges work fine.

[hendrixhc 10,921]

The black shit on the board is where flux from the solder has leached out or the adhesive of the copper track has started to break down. A 2 watt resistor will emit a certain amount of heat and that combined with the vibration of the car will cause the solder joint to fail.

 

More than likely scrubbing up the substrate with isopropyl alcohol and re soldering in the resistor will rectify the fault. Just remember to leave an air gap between the substrate and resistor so it doest become heat effected and it also allows the component to expand and contract with heat.

[Nath 1,975]

The black shit on the board is where flux from the solder has leached out or the adhesive of the copper track has started to break down. A 2 watt resistor will emit a certain amount of heat and that combined with the vibration of the car will cause the solder joint to fail.

 

More than likely scrubbing up the substrate with isopropyl alcohol and re soldering in the resistor will rectify the fault. Just remember to leave an air gap between the substrate and resistor so it doest become heat effected and it also allows the component to expand and contract with heat.

Cheers dude. What about the fact it wasn't getting any resistance when I put the multimeter on it (had someone else double check for me). It was off the board when I did.

[hendrixhc 10,921]

As Crazy said a resistor would usually only go open cct. if that was the case i would expect to see scorching. However, in saying that so long as you are using the multimeter correctly (  ) it must be Open. 

 

The other thing you can do if that big arsed resistor doesnt fit is use two 140ohm X1 wattt resistors in parallel. This will give you 70ohms resistance and the correct power rating.

[Nath 1,975]

Had my dad double check it, he was a sparky back in the stone age. I'll see if the big one fits tomorrow arvo when I get home from work.

[Nath 1,975]

So I took this from the temp gauge on the ZK fairlane dash.

 

Similar but not exactly the same -

 

Top reads different but bottom is 68 ohms J, same as the other.

 

Reckon I'll be ok to use it? Also what about the little sleeve thing on the leg?

 

[Crazy2287 1,886]

Sleeve thing is just heat shrink to insulate it from shorting to another component or earth... Sure you should be fine to use it, but did the ceramic resistor not work?

And for shits n giggels did you take a measurement across this resistor and compare it to the "damaged" one?

[Outback Jack 6,352]

Heya mate, looks OK to me , its the resistance and type of resistor that needs to be the same. The sleeve on the leg of the resistor may be covering a diode that stops power going the wrong way, if you can slide it off and/or there is nothing under there, and it was to stop it contacting other parts of the board.

Sometimes the lettering on the top changes over time, should still be 2 watt.

Double check with Dave..... just to be sure.

 

 

Jack.

 

edit- Crazy beat me.... LOL

[Nath 1,975]

Gave the multimeter back to Dad so didn't get a chance.

 

Pretty much just said f*ck it and threw it on. Didnt fix the problem though (made a thread about what's wrong now.