Have HVAC Questions? Ask an HVAC Expert for Answers
Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.
Due to the age of your unit I can't locate any specs for it. Do you have a wiring diagram pasted to the back of one of the compartment panels? If you do then I need a clearly focused picture of it. You can post a pic here by clicking on ADD FILES next to the SEND button
There's not a lot I can do without one. I did some digging and all I have for a hard copy in my files is a parts list for this model. Maybe one of my colleagues has more info. I'm going to open this backup to my colleagues so one of them can help. Please don't respond (even to acknowledge this post)until you get a response from us. If you respond first it will only delay your answer.
Hi I'm Brian and I'm here to help! If you can remove the blower door panel and find the exact model number that will help. I have many Armstrong/Lennox/Ducane manuals and I likely have yours as well but I will need the full model number to give you proper guidance!
Thank you. Let me see if I can locate the service manual and I'll be back shortly.
Unfortunately I do not have your manual or wiring diagram. I only have the Ultra model back to the 90% model.
The fact that your inducer motor comes on and that's where the ignition sequence stops, indicates your inducer airflow pressure switch is not working right. Click Here for a picture of the updated pressure switch for your model furnace. Click Here for a link to that part sold online. If you TEMPORARILY put a jumper across the two wires on that switch when the inducer fan is running (the switch is low voltage) and the burners light off then that confirms the pressure switch is acting up. Sometimes removing the air line to the switch and clearing the line and the barb it attaches to on the furnace will solve the issue as well. Sometimes however, it is actually the switch itself that has failed. Without the manual and wiring diagram this is the best advice and guidance I can offer.
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Ok, let's go another route then. Can you locate the ignition control module. This is not the fan control board or priinted circuit board but the ignition module. If you can give me any name or number info off of that it will help us. If you could take a picture of it and upload it here using the 'Attach Files' button near the dialog box where you type responses to me, that would be even better!
Yes, you're right. Can you give me any into you can get off the gas valve please?
Thanks, ***** ***** like an SV (Honeywell Smartvalve) but I couldn't tell which one. Let me pull up the manual for that valve and we'll go through it together.
Sorry for the slow response. I had to step away for a few minutes then read the manual and type my suggested steps.
Click Here for a pdf of the Honeywell 9501 smartvalve product sheet. This manual covers several smartvalves. The schematic we will follow is on page 6 in figure 9. I realize your fan timer board may be diifferent but for our purposes this diagram will work for trouble shooting.
Before we start trouble shooting the wiring, disconnect the ignitor plug and measure the resistance between the two hot surface ignitor wires with your meter set on 10k or so. Let me know what it reads. Then we can do the next steps below:
Since the airflow switch doesn't appear to be the issue, you should have 24Vac between 24 volt common and 24Vac Hot on the 4 pin connector on the SV and also between the 24Vac common and 24 volt thermostat or pressure switch terminals on the SV when calling for heat and the inducer fan is running.
Do those tests and let me know what you find.
Ok, take the setting down to 2k or even 200 ohms and tell me what you read. thx
That's awfully low. I would suspect the ignitor. Did you do the voltage tests? That will tell us if the furnace is good up to the point of turning the HSI on. Specifically with the heat calling, inducer fan running do you have voltage at 24V common and 24V thermostat/pressure switch on the valve? Make sure you orient the 4 pin connector right in comparison with the figure in the pdf I sent. It's easy to get turned around with that connector!
Ok that tells me the circuit is fine all the way to the valve. It also tells me the ignitor is trying to draw too much current. It's time to replace the ignitor. Is that the tubular type ignitor with the shield with holes in it?
Ok the model number for your ignitor is a Honeywell Q3400. Click Here for a link to an online supplier. If you do a search for that part number you will find some aftermarket ignitors that are less expensive. I have no judgement on whether they are as good. I can't tell but on some of those models you actually had to remove the gas valve and unpipe the burner assembly to get at the ignitor assembly. It looks like yours may be like that. I just can't tell from memory. It should be obvious how it needs to come out though.
I actually just found it at my favorite online supply house. Click Here for the part and Click Here for the instructions for it.