gas dryer issue- need help from anyone who knows multimeter/res

[the-boulder]

my whirlpool gas dryer quit drying over the weekend. Everything but the heat works fine. I took it apart and found that the ignitor will glow and then click off. From reading various websites it looks like I have a bad gas valve coil.

Now, I went and bought a multimeter to test the resistance of the coils based on what a website told me the readings should be. I read the directions on the multimeter and think I have it right, but had a question about the results.

There are two coils- one is a 3 prong and one is a 2 prong. Here are my readings.

3 prong- tested term 1 and 2 and got 1322- website says resistance should be 1365-

test terminal 1 and 3 and got 564, website says it should be 560.

On two prong, I test 1 and 2 and get 1295 and website says it should be 1220.

So, what should I take from these results? Are these far resistance readings off enough to be causing the problem? Do the results show that both coils are bad?

Thanks-

[Vaevictis]

There's not enough information there to know for sure. It's impossible to say without knowing what kind of variance in the resistance the circuit will accept. Where it says what it should be, it might have a +/-%; double check to see if it does.

My gut tells me no -- the most likely cause of a problem due to variance in resistance is either overcurrent or an open circuit; if you're reading a resistance, it's not an open circuit, and the overcurrent that would result from your reported values is very small, and not likely to cause problems unless the system is extremely sensitive.

EDIT: The units for those numbers... Ohms, right?

[the-boulder]

ah ok, so here is what the site said specifically to do:

Using your ohm meter, measure the resistance between terminals 1 and 2. You should get a reading of 1365 ohms or - 25 ohms. Next, measure the resistance between terminals 1 and 3. You should get a reading of 560 ohms or - 25 ohms. The next coil only has two terminals and it should have a resistance of 1220 ohms or - 50 ohms

Being a novice with the multimeter, I thought the -25 ohms. -25 ohms and -50 ohms was just another way to test, but based on your response, it looks like its the variance that is acceptable? Is that correct and based on this additional info, would you say the coils are shot?

EDIT_ oh and I tested with no current to the coils(unplugged from power source)- thats what the website said to do in an earlier paragraph.

[Vaevictis]

I don't know if it's correct. According to my understanding (which I suppose could be wrong), you shouldn't ever get a negative resistance reading from an ohmmeter, so either the passage has some bad information, or they meant to say "+ or -" instead of just "or -". I can't exactly be sure.

If they did in fact mean "+ or -", well, the two prong is outside of that tolerance, so it's certainly not up to spec. Whether it's enough out of spec to cause a problem ... I just don't know.

I'm assuming you can see the igniter coil right? The coils you're testing... are they just insulated wires wrapped around a core (possibly of just air, but metal is likely), possibly encased in plastic, or are they encased in metal?

If you're talking about the parts I think you're talking about, I think these things are electromagnets that turn on, opening the gas valve when the igniter coil turns on. You might run the thing and hold a piece of metal very near to it -- if the piece of metal gets pulled by the magnet while the igniter coil is on, then the coils are definitely functioning... although I wouldn't necessarily say that they aren't if it doesn't. If you try that, clearly, you want to be very careful that you don't touch any part that might be carrying a current... might even want to have someone there to unplug the damn thing if necessary ;)

EDIT: Now, I should say that even if it gets pulled by the magnetic field, the field may not be up to spec... but at least you'll have a little more information than before.

[the-boulder]

thanks for your replies and help, I took the things off and I'll swing by the appliance parts place tomorrow. They are 15 dollar parts, so I'll give it a shot and replace them.

The parts look like this:

http://www.appliancepartspros.com/Appliance-Parts/Dryer-Parts/Dryer-Igniters-and-Gas-Valve-Coils/FRIGIDAIRE-Coil-kit--gas-valve----2-coils-item-number-AP2150379.aspx


and are located here:

http://fixitnow.com/appliantology/gasdryer.htm

[Harry Beanbag]

ah ok, so here is what the site said specifically to do:

Using your ohm meter, measure the resistance between terminals 1 and 2. You should get a reading of 1365 ohms or - 25 ohms. Next, measure the resistance between terminals 1 and 3. You should get a reading of 560 ohms or - 25 ohms. The next coil only has two terminals and it should have a resistance of 1220 ohms or - 50 ohms

Being a novice with the multimeter, I thought the -25 ohms. -25 ohms and -50 ohms was just another way to test, but based on your response, it looks like its the variance that is acceptable? Is that correct and based on this additional info, would you say the coils are shot?

EDIT_ oh and I tested with no current to the coils(unplugged from power source)- thats what the website said to do in an earlier paragraph.


Never take resistance readings with power in the circuit. You take voltage readings when power is present.

And from my experience, the readings you saw look okay, maybe not perfect but very close.