Hot surface igniter

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Old 12-11-07, 02:23 PM
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Hot surface igniter

Hello,

I have an American Standard/Trane furnace with a WhiteRodgers 50A65-843 control and a Norton 271N hot surface igniter. The control is brand new and the igniter is not so new. Just before the gas lights, the igniter will power down rapidly not lighting the gas. I can light the gas with a flame and it will run like a top until the thermostat shuts the furnace off and it's time to kick on the next time. Also the previous board had problems and heated the igniter up ALOT, not sure if that wore it out or what.

Does that sound like the igniter needs replacing? Or could something else be wrong? Also, anyone know if my control board and igniter are compatible?
Thanks
 
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Old 12-11-07, 03:55 PM
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You can ohms test (with a multimeter tester) the two ignitor leads (the ones heading into the burner to the ignitor). They should ohm at about 30 or less.
 
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Old 12-12-07, 09:32 AM
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Originally Posted by ecman51` View Post
You can ohms test (with a multimeter tester) the two ignitor leads (the ones heading into the burner to the ignitor). They should ohm at about 30 or less.

Thanks for that info. I did the ohms test and it toped out at 102. What do you think?
 
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Old 12-12-07, 12:05 PM
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I found this info searching around:

Disconnect or remove igniter and measure its resistance. Cold resistance should be between 50 and 150 Ohms. (The value of the resistance is not important as long as the igniter is not open or shorted).

Fiction: Testing for a good igniter is done by measuring its Resistance (Ohms).
Fact: The test of an igniter is done by measuring the current draw (amps) of the ignition circuit.

Using wrap-around amp. meter - test one leg for amp. draw.
1) NORTON (flat) Igniter - 3.2 to 3.6 amps.
2) CARBORUNDUM (round) Igniter - 2.5 to 3.0 amps.
If amp. draw NOT within proper range - replace the igniter.
If correct amp. draw is present - replace valve.

Not sure what to do now. Anyone know how to do that amp test?
 
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Old 12-12-07, 12:24 PM
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If I were in your shoes, I'd call a supplier and have them tell me what the resistance is on a new one. If he/she says it 22 and yours is over 100, I think I'd go out and get the new one. A furnace guy once told me that if the HSI ignitor was more than about 65 that it is bad. Bad being that yes it will still glow orange, but not quite whitish-orange ENOUGH to ignite. And this is not just theory. I have had to replace several ignitors that glowed orange, but not obviously enough because the new ignitor solved it!

So now we have a contradiction of facts, according to your article.

Yes, I can tell you how to check for amps, but you need an amp meter. A multimeter cannot perform an amps test. The amp meter has a jaw at the end of it that you can squeeze open and get a wire inbetween it. The wires have to be seperated. (i.e., you cannot test any cord that goes to an outlet because they have the hot and neutral wires together, and the amp reading gets canceled out.

But in the case or the ignitor, the two wires are separate. You can test either wire, while the furnace is on and during the call for the ignitor to glow.

Do you have an analog multimeter that you are using where the needle goes from left to right, to get your reading, or a digital. On analog ones you first must touch the two leads to each other to see if it goes to the right to exactly 0, before doing your ohms test (they call that zeroing out the meter). Otherwise if not at zero, any reading you take will be off; sometimes WAY off.
 
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Old 12-12-07, 12:32 PM
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Ok,

I have a digital multimeter. I tested it several times to be sure. It was still a little warm when I started testing and read around 92. As it cooled it started climbing and went to 102. I went back a little later after I posted and hooked the meter back up and it was up to 106.5!

I'm familiar with that amp meter your talking about. I don't think it's the gas valve either though. Thanks
 
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Old 12-12-07, 12:49 PM
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I just went and tested it again. It's steady at 107. I couldn't find the exact specs for my brand but, I found specs for a universal replacement for my brand.

http://www.supco.com/images/pdfs/SSN...000%202007.pdf

It's specs say between 15 to 30.
 
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Old 12-12-07, 03:16 PM
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That's what I'm saying.

Your symptoms are that of a weak ignitor. Can't guarantee it for sure, but a new ignitor would not break the bank (I hope), and these do go out, in due time, anyway. I'd still like to know what the ohms is for one just like YOU have when new. But I'd have to guess it too would fall into the range somewhere of what you listed.
 
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Old 12-14-07, 04:27 PM
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Thumbs up Furnace Fixed!

I bought a replacement ignitor the other day. I got it home and installed it only to find it performing worse than the old one. It measured 120 ohms resistance. I reinstalled the old one, moved the bracket closer toward the flame and it worked half the time.

I went back to the shop for a replacement and found out they gave me the wrong model because the plug matched my old one. It turns out you need a compatible model, your suppose to use your old plug if it doesn't match which the new ignitors come with wiring nuts in the box.

They exchanged it for the right model which measured 60 ohms (much better!). I got it home, put the bracket back where it originally was, installed it and it works perfectly.

I want to give a special thanks to ecman51 who helped me out a ton on PM and on open forum. Much appreciated, thanks!
 
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