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Old 05-08-2012, 10:34 PM   #16
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Lennox Merit problem.


Got a meter? Pull the plug off the ignitor and stick your leads into each wire plug going to the meter, meter set on a/c. If you have a door switch on the furnace then leave it open/out, set the stat on call for heat (setting the desired temperature high), stick meter leads into plugs which should stick in there and hold in place, push the door switch in and hold it in (now allowing power to the furnace and stat) and see what happens. Tell us if you have voltage to the ignitor.

We can (try to) isolate the problem from here.

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Old 05-08-2012, 10:58 PM   #17
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Lennox Merit problem.


The ignitor always glowed. The old one and the new one. Someone else said possible clogged orfices or crossover??
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Old 05-08-2012, 11:03 PM   #18
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Lennox Merit problem.


Ah, I was under the impression it was not igniting.

You could have air in the lines or a clogged gas valve. A manometer would be needed to check pressure.

Does your gas furnace have a drip leg on the steel gas line to the furnace, just before the furnace? That's pretty much an upside down T on the steel gas line used to catch any particles that may be travelling in the gas.
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Last edited by Doc Holliday; 05-08-2012 at 11:06 PM.
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Old 05-08-2012, 11:12 PM   #19
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Lennox Merit problem.


Yes, there is a metal drip leg on the gas line. This would happen towards the end of the last heating season when the furnace was off for a while,but would eventually light after 2 try. don't know if that has any bearing on what might be causing this.
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Old 05-08-2012, 11:22 PM   #20
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Lennox Merit problem.


Call your local gas company and have them check the gas lines. Start there as I think it's free but don't quote me on that. Ask them if it is. Tell them you believe there's air in your gas lines, describe what's going on.
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Old 05-09-2012, 05:48 AM   #21
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Lennox Merit problem.


Would there not be a problem with othere gas appliances I.e. water heater if that were the case?
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Old 05-09-2012, 08:25 AM   #22
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Lennox Merit problem.


Probably but are you not using those appliances for long periods of time as well? Besides, I said the utility company would come out for free. We won't.

At this point it's either going to be you purchase a digital meter and a manometer or start playing parts changer, throwing money at the system. I'd start with the gas valve.
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Old 05-09-2012, 02:07 PM   #23
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Lennox Merit problem.


Called a local hvac tech and he said valves are rare,but could be the circuit board not opening the valve? Is that a possibility? What happens when these boards fail?
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Old 05-09-2012, 03:48 PM   #24
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Lennox Merit problem.


Just hire a tech already. We can go about all the possibilties but without the right tools and your know how of how to use them to diagnose it's anyone's guess on the internet.

A manometer will check gas pressure to and through the gas valve. If the valve is not opening when it should then there'll be no gas pressure through the valve once it's supposed to open. Without a meter to test for 24 votls to the valve than there's no other way to know if the board is sending the 24 volts to open it in the first place.

You said the valve is making a noise, like a "clunk" or a "click" after the ignitor glows. Usually that's the sign that the valve is being sent power. Going from what you've said on here along those lines then I'd say the board is sending the valve voltage. Whether or not the valve is opening would be the question and again, knowing that you said the ignitor is igniting and that then there's a "clunk" sound at the gas valve. Regular 24 volt gas valves all make a distinct sound once they've been sent voltage to open, the clunk or click.

Again, all this diagnosing is over the net and simply a guess. You need to hire someone now or buy some tools.
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Old 05-09-2012, 03:52 PM   #25
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Lennox Merit problem.


Ok, I have a digital multimeter thats not a problem. Should I purchase,an analog manometer or digital?
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Old 05-09-2012, 04:04 PM   #26
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Lennox Merit problem.


If you have a digital then that's good. What you do is simpy pull the two wires off of the gas valve, stick your meter leads one into each spade end (wire) and turn the heat on. Just after the ignitor starts to glow is when the board sends 24 volts to the ignitor. Use a/c voltage on the meter setting.

And if you don't want to remove the wires then simply slide them back a hair to expose the two terminals on the gas valve that the wires connect to and test there, one on each terminal.
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Old 05-10-2012, 12:07 PM   #27
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Lennox Merit problem.


Ok, couple things. Took apart burners and no blockages. Orfices no blockage. 26.5vac going to valve when 'click' is heard. Safe to say it's the valve now?

Another thing, the old ignitor registers 16ohms and the new one 48ohms. Is that still in spec?
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Old 05-10-2012, 12:20 PM   #28
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Lennox Merit problem.


For the one hundreth time, no. It's safe to assume it might be the valve but without a manometer to check the gas pressure to and through the valve then it's simply an assumption that it is failed.
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Old 05-10-2012, 12:27 PM   #29
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Lennox Merit problem.


I thought this was a forum to gain information and not to get yelled at. If the valve is getting commanded to open and the correct voltage but no flame, if it isn't the valve what else could it be.
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Old 05-10-2012, 01:09 PM   #30
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Lennox Merit problem.


Look at your post count and then look at mine. That's how many times I've helped on here.

What there seems to be is a failure to communicate. Either you are not comprehending me saying things the first time around such as using a manometer and then responding properly, acknowledging the fact that I stated a specific and that you understood it as such the possiblility of there being air trapped in the gas lines or that you'd need a manometer to check gas pressure to as well as through the gas valve or I didn't say any of those things.

I'm pretty sure I've said it. Not yelled it either, but said it. Repeatedly.

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