Hello all. Thanks for your help in advance.

I'm having an ignition issue with my gas furnace. Inducer fan kicks on, pressure switch hose / nipple isn't clogged, igniter glows (new igniter, just replaced it), than turns off. Igniters glows a total of 3 times, than system goes into lockout mode. Control board has a LED error code of one flash. Meaning ignition failure (manual says to check gas flow, gas pressure, gas valve, and flame sensor)

I sanded the flame sensor, it was slightly carbonized, but not terrible looking. Replaced it, issue still occurs.

Gas flow is turned on, I haven't messed with gas pressure, as it worked fine before.

Any testing I can do with the gas valve? I ordered a replacement flame sensor just in case. They're a good replacement to have around anyway I hear.

Oh, also testing voltage to the flame sensor, and it appears to not be an issue.

Any other ideas / things I can test?

 

Can you post the brand and model # of the furnace? Can you tell whose ignition system they used and the model #? Do you have a voltmeter? Are you getting voltage to the gas valve terminals?

 

well, its a kenmoore, but i can't find a model #. appears to be a goodman / janitrol control board. similar to this one



and its a hot surface ignition system. is that what you mean?

I do have a multimeter and can test the gas valve probes. I'll post those results as soon as I get a chance to do this.

 

apparantly i don't know how to use the multimeter to test the gas valve. when i tested the flame sensor, all i did was place the black probe to ground, and the red to the sensor's terminal.

the gas valve has two terminals. one i believe is power, the otehr i'm not sure. it leads to some sort of sensors? around the gas manifold area. (one on top, and one on each side) I have no idea what they are.

either way, i wasn't getting a reading when i tried to probe the one i thought was power along with ground.


to make things more confusing, the unit actually fired up and provided heat one time while testing. i haven't been able to get it to do it since, but it worked one out of the past 15 tries :\

 

Set the meter for ac volts and put one probe on each terminal on the gas valve. Are all the wiring connection tight and not corroded?

 

Ok. I'll give this a shot when I get home today. I'll also post pictures of the valve. I don't recall anything looking corroded or out of the ordinary.

On a side note, I did fire up a second and third time. Seems to be starting more frequently, but it did go into lockout mode about 2 out of 5 times.

 

In your first post you said you sanded the flame sensor then replaced it. I'm thinking you meant re-installed it back in the furnace? Flame sense rods get a carbonized film on them that you can't see. Try putting in a new one.

 

apologies. correct, sanded, than re-installed. I'll order a new one as well. Can't hurt to have a spare if it doesn't fix it.

 

OK- sounds good. Be sue to clean the spot where the flame sensor attaches to the furnace/burner. These systems rely on a ground circuit back to the module/board.
Let us know what happens. Thanks.

 

ahh, good idea.

question though...if it were the flame sensor, wouldn't it fire up at least, and than shut off, due to thinking theres no fire, just gas?

the gas is never expelled when it goes into lockout mode.

 

Well, in some of your posts you indicated that it fires sometimes, then goes out. That's why I thought about the sensor. We need to get a voltage reading at the gas valve terminals when it's not working right. That will tell us if the gas valve is bad or not.

 

ok. i'll post pics of the gas valve tomorrow while i'm on a faster connection, but i did take reading at the terminals. there does appear to be some corrosion on one side of the valve.

i get 0 volts when the igniter is glowing and eventually when it goes into lockout. now get this, if i take off the wires leading to the terminals, and test them off of the valve, i get around 24 volts.

now after powering off furnace and back on again to clear lockout state, i tested the terminals with wires on. it took 2 tries with the igniter and on the 3rd try, i got 24 volts to the valve and it opened up, providing heat.


heat stayed on for a few minutes, than gas must have shut off, igniter tried to turn it on again, and eventually it shut off and went into lock out state.

 

here are pics.

the gas valve as a whole


pics of the corrosion on the right side. no idea what thats from. the AC condensation pipe is right above this, so maybe this leaked on it before I bought the house.



and a close up of the model number

 

so should i go ahead and order a gas valve? anyone know where to find this model? arnolds doesn't seem to carry it

 

So you're saying that at times you get 24v at the gas valve and it fires up and other times you don't get 24V to the gas valve during a call for heat ? Not sounding like a valve issue at this point.

 

correct. sometimes i get 0v at the gas valve while the igniter is glowing waiting for gas to be delivered. other times, i get 24v at the valve and the gas comes.

if i take the wires off the gas valve and test them while off of it, i get 24v every time.

 

Hmmm.... I might for kicks and giggles re-do the connectors on the wires. If you get 24V everytime with the wires off it sounds like a bad connection somewhere.

 

can i replace the wires altogether? where can i get them?

 

If you get 24v to valve everytime after ignitor glows, then gas valve is sticking.

If you sometimes get 24v to gas valve, then sometimes dont check wiring from board to g.valve.

If you pull wires off board and check right at terminals to g.valve and have 24v everytime, wires have bad connection.

If you sometimes have 24v at board and sometimes dont, you have intermittent problem with board, replace board.
One other thing, make sure you have a good ground.

 

thanks for the help guys. its been working pretty regularly up until yesterday. (it got real cold here again a few days ago)

anyway, how can i check the GV wire? its in a 9 wire wiring harness.

also, the limit switches all seem to be ok and not corroded. should i check those individually as well (there are 4)? they have little switches on top of them that don't seem to be popped out or anything like that.

i only seem to have trouble when its really cold in the room the furnace is located in. could the issue be the board is getting cold and not working properly? how finnicky are these boards? this could possibly be the original board and its pushing 15 yrs old.

found the furnace model number as well.

Goodman GMP 075-3 , looks like it was installed in 1993.

 

There is a phenomenon (not really, it's explainable) where when you test across hooked up terminals that are being used, the current falls off.

Based on the fact you always get 24 volts when the wires are disconnected, leads me to believe the board is good.

I think your only problem is the HSI is not being proven. Either impedence is too high in the HSI itself, and/or it's resistance is too high. Ohms test the ignitor's 2-wire leads that go TO the ignitor (not the ones coming from the board!)and tell us what the ohms are. If good, it should be about less than 30, but they can still work I believe around 65.

 

ok, disconnected the power to the HSI, than Ohms tested the ignitor.

Resistance was about 75. This is a brand new ignitor, but are you thinking maybe its not the right one?

 

so where do i check to see the proper resistance for my furnace's ignitor? Where is that level set?

 

You unplug the jack leading to the ignitor.

There should be two wires that come from the board and then turn into a jack, where at that jack, the two wires leading to the ignitor are usually thinner white wires. You unplug that jack.

Then take a multimeter and set it to the lowest range on the ohms scale. Touch one test lead to one ignitor wire-end and the other test lead to the other ignitor wire- end, at the same time. Then see what the reading is. On an analog multimeter (zero-out the test meter first), then when testing the needle will swing from left to almost all the way to the right, if it is good. On a digital one, you may get an actual reading below 30, if new-like good condition.

 

Sorry for the confusion. I posted those results. a reading of around 75 ohms.

I was asking in my second post if there was some sort of posted specs for my particular furnace to see what those numbers should be.

You said 30. Mine sounds way hi. Should I replace ignitor and try again? or test resistance on the other 3 ignitors i have and use one that's around 30? (1 is the ignitor i replace, the other 2 are new ones i have for spares)

 

ok, some more info for ya.

all 3 of the flat style ignitors had resistance of 75 -85. none of the boxes had info on cold resistance for these. I assume since their all in the same range, they're normal.


the 1 "universal" style "stick" ignitor had resistance of around 20. (info on box says cold resistance is about 30ish)

 

Goodman service book says the ignitor should read 40 to 75 ohms when cold. I'm thinking you might have an intermittent board issue.

How are you guys posting pics? I haven't quite figured that out.

 

Ok. I read in a few other threads that these particular control boards have issues when they get cold. Maybe a new one is in order. Not that expensive or difficult to replace. I'll go ahead and order one.

daddyjohn, pics aren't that difficult. Your pic has to be online somewhere already though. (you can upload them yourself to a hosting site, i.e. www.putfile.com, and than take the link of that picture online i.e. www.whatever.com/picturename)

Than there's a little icon of a mountain in the reply tab of the forum. you click that and insert the picture's url and whalla!

Hope that helps.

I'll post results of the new board when that's done. Also, if anyone can think of anything else, lemme know.

 

That silicone carbide HSI, which is the ceramic insulated flat one, is the one I recently replaced by installing the better stick variety you also illustrated. I had 22 ohms from my GB digital tester, cold.

 

Thanks. any other ideas than? Do you agree with the control board diagnosis?