Do cement resistors have specs resistance when cold?

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DreamV4

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Resistor says 2.2 Ohms, but I checked 1.5 Ohm. Is it normal for cold resistors? Maybe it is expected to have 2.2 ohm after it gets hot?

Well, it looks like I found an answer.
I bought 5 of them, checked one, it was 1.5. I installed 4 and just checked last one, it is 2.2 ohm!!! So one or more of them are defective.
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02GF74

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These resistors typically have 5-10% tolerance, so 1.5ohm is well outside the range. I would expect resistance to be specified at 20c (room temperature)

I looked up a data sheet of vishay brand, similar to the ones you have, and they have thermal coefficient of 300 ppm.. I calculate the resistance with a 100C rise to be 2.27 ohm.
 

DreamV4

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thanks! I will check all 4 installed resistors and go from there.
 

Screwloose

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Resistor says 2.2 Ohms, but I checked 1.5 Ohm. Is it normal for cold resistors? Maybe it is expected to have 2.2 ohm after it gets hot?

Well, it looks like I found an answer.
I bought 5 of them, checked one, it was 1.5. I installed 4 and just checked last one, it is 2.2 ohm!!! So one or more of them are defective.
I do not know if you have considered this, but you need to NUL out your test leads on the meter before measuring, as all test leads have a resistance in themselves. Especially if you are doing fine measurements.

Put meter on resistance, touch the leads, and any/if resistance is showing take that from your final reading when measuring.
 

crynool

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Is 10W sufficient?
12V / 2Ohm is ~~72Watt?

Asking, because I have NO idea about it ... :)
 

DreamV4

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Is 10W sufficient?
12V / 2Ohm is ~~72Watt?

Asking, because I have NO idea about it ... :)
you are my personal trainer, you know everything!!! :) OEM fuse is 10 Amps, it means current for each coils is not more than 2amps. Right now I have 7.5A fuse
 

02GF74

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1.5 ohm is a fair way off 2.2 ohm. Ensure you are measuring the resistor as isolated as possible when measuring its resistance, by that I mean disconnect the lead the ignition module and if possible from the COP.

I'm sure you know, but don't hold the probe tips onto the resistors with your fingers.
 

crynool

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you are my personal trainer, you know everything!!! :) OEM fuse is 10 Amps, it means current for each coils is not more than 2amps. Right now I have 7.5A fuse
I am? Well, I got promoted. Yeha :D

Btw, we have a Spinning Instructor who is an Ex-COP ... his lessons are REALLY challenging ...
 
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