DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > Troubleshooting Ignition Control Board and Ignitor




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Old 12-30-2012, 03:58 PM  
69-er
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Default Troubleshooting Ignition Control Board and Ignitor

On my ICP HVAC unit, mod# PGF336080K00A1, I am getting gas flow to the burners but no spark at the electrodes. I am assuming that since the gas valve is opening, that means all the limit and rollout switches are working. I also have power coming out of the pressure switch.

It seems that the round spark ignitor module or the ignition control board is inop. The ignitor module, (#1173831 superseded by #1177395) has four wires going to it. Blue from the gas valve input, green to ground, and the remaining black and yellow wires coming from the ignition control board. Since I don't know what voltages I should be reading from the board, I have no idea which component is bad.

I didn't see any other posts on this. Anybody know if there is a past thread on this or what voltages I should be getting? Or, is it common knowledge as to what component is probably bad?

Thanks!

Larry



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Old 12-30-2012, 04:12 PM  
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Blue from the gas valve input, green to ground, and the remaining black and yellow wires coming from the ignition control board.
If you post a legible schematic showing this module, with these few connections its gizzards and normal readings can probably be inferred.


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Old 12-30-2012, 09:01 PM  
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Thanks Wuzzat?,

Here's the diagram...

You can see at the bottom how the "Remote Sparker Control" is apparently controlled by the "Ignition Control Board" at the top. It looks like it is continuously powered by 24VAC along with the the gas valve whenever heat is called for and the black and yellow wires somehow tell it when to turn on and off.

It looks those two also have 115VAC on them but I don't know when they would be powered.

hvac-unit-wiring-diagram.jpg  
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Old 12-31-2012, 11:57 AM  
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I'd think the 120vac and the 24vac module inputs should read a few ohms and the secondary (between ground and the sparker), several kilo-ohms.
There may be a relay inside the module that enables the module to spark as long as 24vac is applied and the spark is stopped by discontinuing the 120vac.

Take some voltage readings during the time when you are supposed to have sparks. That should isolate the problem upstream of the module or in the module (or both; the module may have failed and caused upstream failures).

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Old 01-01-2013, 03:03 PM  
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Don't know why I didn't think of this earlier, but this unit for my shop is basically the same one on our house too. I toyed with the idea of using its parts for trouble shooting but didn't want to risk burning those up too and not have heat in the house!

So, I took voltage readings of the house unit and compared them to the shop's unit.

The black and yellow wires have voltage at all times, whether the furnace is running or not. Black-117v, yellow-124v. When it's sparking the black wire voltage goes up to 124v. Don't really know how it knows when to stop sparking other than it might sense the flame through the electrodes.

The shop unit has the same voltages. I'm going to replace the remote ignitor module.

Thanks for your suggestions!

Larry

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Old 01-01-2013, 03:36 PM  
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Don't know why I didn't think of this earlier, but this unit for my shop is basically the same one on our house too. I toyed with the idea of using its parts for trouble shooting but didn't want to risk burning those up too and not have heat in the house!

So, I took voltage readings of the house unit and compared them to the shop's unit.

The black and yellow wires have voltage at all times, whether the furnace is running or not. Black-117v, yellow-124v. When it's sparking the black wire voltage goes up to 124v. Don't really know how it knows when to stop sparking other than it might sense the flame through the electrodes.

The shop unit has the same voltages. I'm going to replace the remote ignitor module.

Thanks for your suggestions!

Larry
That sounds good but don't count your chickens quite yet.

Label both modules so you know which came from which furnace, and ohm out each.

With four terminals plus the metal housing (if it has one) that's
Housing to term 1
to 2
to 3
to 4

then

1 to 2
1 to 3
1 to 4
2 to 3
2 to 4
3 to 4

assuming the module insides are not polarity sensitive. Otherwise it's twice as many readings.

With modern electronic digital ohmmeters/DVMs there is probably no risk of the meter's test current damaging the module.
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Old 01-09-2013, 01:55 AM  
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With modern electronic digital ohmmeters/DVMs there is probably no risk of the meter's test current damaging the module.
That dosn't sound good!

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Old 01-09-2013, 06:53 AM  
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With modern electronic digital ohmmeters/DVMs there is probably no risk of the meter's test current damaging the module.
That dosn't sound good!
Well, with the old analog Simpson 260 you will almost certainly damage today's electronics.

Maybe I'm over cautious.
If your meter is powered by a 9v battery you're almost certainly good.
If it's one of these analog meters with 1K being the center of the resistance scale and it's powered by a 1.5v battery, your ohm test current is 1.5 mA and this may be OK also.
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Old 01-09-2013, 05:00 PM  
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Agree; Any digital meter has a low enough impedance not to overload any digital or computer circuits. Mosfet circuits are very susceptible to damage from this, along with static discharge damage. Which, BTW, my replacement board was packaged in a antistatic bag. I think that was overkill. It looked like any typical ignitor board I used to work with as an RV tech. We could throw them around and they would always work!

UPDATE: It was was too late to meter out the leads as you suggested, I already ordered the new board! But, it works great now. Thanks for your help!

Larry

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Old 01-10-2013, 11:13 AM  
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Good job, good outcome.

Sometime before the next problem you should measure resistances for your motors and coils; it's one spec that is hard to find, easy to measure, and can be useful.

Bryant sent me a few pages for free from the factory manual on my '82 furnace and I have spent some hours with these pages and a voltmeter, trying to get comfortable while sitting on a 5 gal. bucket and poking around.



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