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 Repairing and Servicing Lennox Products
 Repairing / Servicing Lennox Gas Furnaces
 Pesky Igniter Problem G60UH-48B
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Skipweb

2 Posts

Posted - 12/10/2006 :  10:50:55 PM  Show Profile  Reply with Quote
Hi -I have a G60UH-48B-090X-04 furnace/AC which is a couple years old, and am experiencing igniter problems. This was the diagnosis of the HVAC Tech who came out to figure out why the heater was not coming on. His diagnosis (bad igniter) was based on LEDs DS1 and DS2 flashing alternatly (slowly). He replaced the igniter and the system worked for about 12 hours and then begin to behave in a hit-or-miss on subsequent heating cycles. He came out again, took some voltage readings from the igniter leads out of the circuit board, tightened a few leads leading and wella - the system worked, with the igniter glowing cherry red, thus allowing the burners to fire up. 24 hours later, no cherry red igniters, no heat. Which is where I am today.

Current situation: I took voltage readings all of the way to the igniter and got 99 volts, however the igniter is getting hot, but not cherry red. I also checked the IGN00117 silicon nitride igniter by itself, which yielded 18 ohms across the leads. Not sure if this is considered "open" or normal. Also, I did a crude grounding check between the Neutral and terminal "C" (per how to check for proper surelight grounding topic)which yielded 81 mv. In any case, something is either causing the igniters to go bad, or there may be a circuit board problem (not feeding enough amps to a good igniter?), or I have a flaky ground.

Any advice is greatly appreciated !!




SW

Cozy.Support

5759 Posts

Posted - 12/10/2006 :  11:03:21 PM  Show Profile  Reply with Quote
If my memory is correct, the Surelight board only puts out the required voltage to make the igniter work. It has a routine that it goes through that causes the igniter to operate on the minimum amount of voltage needed to make the furnace fire reliably.

If the igniter is glowing, but the furnace is not igniting, I would check the location of the igniter. You also need to confirm that you are indeed getting 24 VAC to the gas valve during the ignition sequence and that the valve is opening to provide gas to the burners.
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Cozy.Support

5759 Posts

Posted - 12/10/2006 :  11:08:02 PM  Show Profile  Reply with Quote
Here is the exact wording that Lennox uses to describe how the igniter voltage is adjusted by the Sirelight board.


The SureLight control board has an added feature that prolongs the life of the ignitor. After a successful ignition, the SureLight control utilizes less power to energize the ignitor on successive calls for heat. The control continues to ramp down the voltage to the ignitor until it finds the lowest amount of power that will provide a successful ignition. This amount of power is used for 255 cycles. On the 256th call for heat, the control will again ramp down until the lowest power is determined and the cycle begins again.
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MechAcc

1499 Posts

Posted - 12/11/2006 :  05:09:12 AM  Show Profile  Reply with Quote
Had a situation where one of the pins of a Molex plug was not fully seated and locked into place. Would shut down power and disconnect every plug and check the positioning of all the pins male and female. If you find one recessed grasp that wire and slowly push on it. You should hear a snap once it is positioned correctly. Reassemble the plug and the disconnect it again and recheck the pin to make sure it stayed in position then reassemble. Even check the plugs for the igniter. Make sure all of the plugs are locked into place. If you don't find a pin unseated then would ohm check the igniter circuit from the control board plug. I would then move the wiring harness around to see if the ohm value through the igniter is lost. One of the molex pins for that circuit may have cracked or a wire that is separated and making intermittent contact.

The problem could also be an intermittent problem in the control board. Don't qoute me but believe the boards have a 5 year warranty on the original install.

I am not an employee of CozyParts. The opinions that I post are my own.

Please have your furnace inspected annually by a qualified service technician. Have them test the undiluted combustion gases for proper combustion and carbon monoxide production.

Get a good Carbon Monoxide Alarm. Replace it according to manufacturers recommendations usually every 3-5 years. CO concerns are not just for the winter but 24-7. UL approved alarms alarm high. For a low level alarm do a search for CO Experts or NSI 3000 a low level CO monitor.
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Skipweb

2 Posts

Posted - 12/11/2006 :  5:09:12 PM  Show Profile  Reply with Quote
Great comments from cozy.support about the surelight board, where the voltage is ramped down for 255 cycles. : Is there anyway to reset this, so that it starts again in full voltage? I assume that simply disconnecting the power will not cause a loss of memory on the control board.

Thanks for the tips from MechAcc on checking the Molex plugs. I will check the ohm value of the circuit through the igniter while checking the connections to see if there is a poor junction somewhere between the circuit board and the igniter.

After I wrote the initial question, I noticed that the igniter installed the other day by the Tech was from American Standard. It looks like a perfect fit for the original. I wonder if this combined with the 255 cycle voltage adjustment has something to do with it. However, it did glow cherry red for a few days, stopped working, and began working again, and stopped working.

Thanks….SW


SW
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Cozy.Support

5759 Posts

Posted - 12/11/2006 :  6:29:51 PM  Show Profile  Reply with Quote
Not sure what American standard has... the hot surface igniter may be compatible with the surelight board, and it may not.

I do not remember for sure about re-setting the ignition count on the igniter voltage.. maybe MechACC knows.
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Cozy.Support

5759 Posts

Posted - 12/11/2006 :  7:31:07 PM  Show Profile  Reply with Quote
Just in case anyone happens across this post later, the routine that the Surelight board goes through to set the minimum voltage for the igniter, is exactly the reason why the gas line to a new Lennox Surlight furnace installation should be bled before turning the furnace on. If you have a lot of air in the gas line, you will cause the Surelight control to set the operating voltage higher than it needs to be, because the furnace will fail to ignite on the first few tries while you are purging the air from the gas line through the furnace's burners. This can actually lead to premature igniter failure.
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MechAcc

1499 Posts

Posted - 12/11/2006 :  7:34:14 PM  Show Profile  Reply with Quote
Believe that removing 120 vac and reapplying power resets the counter.

I am not an employee of CozyParts. The opinions that I post are my own.

Please have your furnace inspected annually by a qualified service technician. Have them test the undiluted combustion gases for proper combustion and carbon monoxide production.

Get a good Carbon Monoxide Alarm. Replace it according to manufacturers recommendations usually every 3-5 years. CO concerns are not just for the winter but 24-7. UL approved alarms alarm high. For a low level alarm do a search for CO Experts or NSI 3000 a low level CO monitor.
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