Armstrong Ultra SX90 LP gas furnace

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Old 10-28-12, 06:54 AM
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Armstrong Ultra SX90 LP gas furnace

Hello, Im new to the forum. For a few years now, the exhaust fan(I call it clean out fan but its not nearly as loud or powerful as the main blower) turns on when the thermostat calls for heat and runs for several minutes then shuts off. Other times the furnace will come all the way on and heat sometimes as long as it should other times it will shut off too soon. This year when I powered it up the exhause fan ran for 25 minutes or so and the heat never game on, I never heard the burners light up. I turned the power off to the furnace a few times and the thermostat and then it started working. Then we didn't need it for a few weeks and Friday morning the exhaust would run and run and run for like 40 minutes until I finally turned it off. I haven't tried cleaning the flame sencor yet or checking the ignitor for cracks. I'm not sure where they are and everything I've read seems to indicate the gas valve. I have a gas valve with this model number on it, VR8204H 1097 and from what I can tell it is a honewell. SHould I go ahead and replace the gas valve or should I clean the flame sensor (formally called a thermocoupler from what i have read) or what? Also, I don't know which gas valve to order if it is bad. I would appreciate any help you all could give me. Thanks!!!
Mitch
 
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Old 10-28-12, 07:10 AM
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Welcome to the forums! I have made your post it's own thread so that it is less confusing as every furnace and situation is different. What you need to do is: with a call for heat from the thermostat, sit in front of the furnace and note the sequence of events that happen. report that information back here. If your furnace has a control board with a LED light that flashes trouble codes then that information would also be helpful. Help us to help you and it will make things easier so that you are not just guessing and replacing unnecessary parts.
 
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Old 10-28-12, 07:26 AM
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Thank you so much!!! Ok, the thermostat calls for heat, the exhaust fan turns on and after about a minute I hear a click and then what sounds like an ignitor trying to light, for instance like really fast sparks and that happens for about a minute then I hear another loud click and the exhaust fan runs the entire time and continues to run after the second loud click. I have the front panel off of the furnace but I don't know where to find the control board. Sorry, I'm not very knowledgable with furnaces.
 
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Old 10-28-12, 07:34 AM
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I just noticed, after the first time it tries to light and then shuts off, it continues to try and the exhaust fan keeps running, with several clicks on and off, then there are more clicks at random intervals, sometimes fast and sometimes slow, but I just heard about 20, sorry I'm trying to be specific, and the exhaust fan is till running
 
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Old 10-28-12, 07:36 AM
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It sounds like you have a honeywell spark ignition module.

Can you see the pilot light up through the viewing window of the burner box?

This type of system lights a pilot and then once the pilot is proved by the ignition control it opens the main gas valve. You need to know if the pilot lights at all.
 
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Old 10-28-12, 07:44 AM
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The next check will require a voltmeter and knowing how to use it. IF you don't have one or don't know how to use it then it will be time to call a Pro.
 
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Old 10-28-12, 07:47 AM
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Yes, I just noticed that the pilot is lighting and is lit now then I hear a series of clicks coming from a board in front of the large blower in the bottom of the furnace the clicks are random sometimes close together and sometimes a little further apart, the pilot continues to burn for a while, then there is a louder click up higher in the furnace and the pilot goes out and then the exhaust fan continues to run. Thanks again for the help and the quick responce!!!!
 
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Old 10-28-12, 07:51 AM
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you really need a voltmeter to go any further. But, on a whim, on the inducer (small exhuast blower near the burners) there should be a rubber hose....remove it from the blower and look inside where the hose was attatched. Make sure that is clear and no debris is present.
 
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Old 10-28-12, 07:53 AM
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I have a volt meter here and ready, can I remove the hose while the exhaust fan is running and the furnace is powered up or should I turn the switch off to kill power to the furnace?
 
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Old 10-28-12, 07:59 AM
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I would shut the power off first......... Can you get a model number off the module like I posted a picture of so that I know exactly which terminals you have. Or a picture showing the module with the connection labels would be even better.
 
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Old 10-28-12, 08:00 AM
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I turned the power off and removed the hose, it is clear, with very little force I blew through the line, then removed it from the metal circular device that is attached to the furnace housing and it was clear, I reconnected the hose and tried the furnace again, still doing the same thing.
 
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Old 10-28-12, 08:06 AM
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HEre is the pic you requested
 
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Old 10-28-12, 08:10 AM
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WIth the furnace running and a call for heat from the thermostat check for power between terminals 5 and 6 on the honeywell igniton control. Leave you leads attatched during all the clicking to see if the power drops out.
 
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Old 10-28-12, 08:22 AM
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Ok, so terminal 5 says 24V with gnd under it and terminal 6 says 24V so I touched my black lead of my volt meter to terminal 5 and red lead to terminal 6 and read 24 or 25 volts during the entire cycle, before during and after the series of clicks, did I do that right, or should I have touched teh black post to terminal 4 and tried 5 and 6 with the red post to make sure they both were outputing power?
 
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Old 10-28-12, 08:30 AM
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you performed the test correctly. Next, did the pilot light and stay lit the entire time? If yes, then you need to test for voltage between terminals 1 and 2 after the pilot it lit. DO you have a meter that can measure DC micro amps (uA)?
 
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Old 10-28-12, 09:04 AM
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I don't think my meter will measure that, i am going to have to borrow one from a friend and I will get back to you I have to go out of town for the night but will be back MOnday around 4:00 pm central time but I will have internet access even while I'm gone if you think of anything else. The pilot stays on throughout the series of clicks, then there is a loud click I think from the gas valve and the pilot burns out, then the exhasut fan continues to run and the whole sequence repeats itself. I have included a pic of my gas valve and multi meter. Thanks so much for the help!!!!!!!
 
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Old 10-29-12, 01:56 PM
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I am back home and now have a meter that will measure DC micro amps. However I'm not sure where to touch the black probe and where to touch the red probe. As soon as someone has time to help me out with this, id really appreciate it.
 
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Old 10-29-12, 03:50 PM
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Testing flame signal : remove wire on terminal 8 and put one lead to the wire. Put the other lead on terminal 8. This must remain in the circuit while the pilot is lit. Did you ever check voltage between terminal 1 and 2 with the pilot lit?
 

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Old 10-29-12, 03:52 PM
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Hello, thanks for getting back to me! No I didn't check between terminal 1 and 2 I just got the correct volt meter to measure the micro amps in DC but wasn't sure how to perform the test. I didn't know if the red post of meter should touch terminal 1 or 2 and if the black should be grounded or what?
 
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Old 10-29-12, 04:12 PM
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I also have a little better understanding of what is happening. The thermostat calls for heat, the exhaust fan comes on (clean out fan, not the blower) this runs for about a minutes, then the gas valve clicks loudly and I hear what I think is the heating element turning on that lights the pilot, then the pilot lights and I can see it burning through the window. THen the ignition control module makes a series of clicks on and off in different sequences for a few minutes, then the gas valve clicks loudly and then shortly after that the pilot burns out and the exhaust fan continues to run. The main burner never lights and the main blower unit never kicks on. HOpe this helps a little.
 
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Old 10-29-12, 04:12 PM
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Insturctions for testing flame signal are in post # 18. Checking voltage between terminals 1 & 2 should be done separate from the flame signal test.
 
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Old 10-29-12, 04:16 PM
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THanks! when I test for the flame signal following post #18 procedure, am I testing for DC micro amps or something else, sorry for my inexperience.
 
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Old 10-29-12, 04:29 PM
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Flame signal is measured in DC micro Amps.
 
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Old 10-29-12, 04:48 PM
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I was getting a reading of 0.1 micro amps and sometimes 0.0 and sometime 0.2. When I completed the circuit with the amp meter the clicking sounds changed, they sounded differently. Then when the gas valve clicked and the pilot went off, I had a steady reading of 0.0
 
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Old 10-29-12, 04:51 PM
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You should have a reading of at least 1.0. Now you need to remove and clean the flame sensor with steel wool or a steel or brass brush. Follow the wire you used to test the signal with back to the flame sensor.
 
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Old 10-29-12, 05:46 PM
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Well, I cleaned the flame sensor but I was unable to figure out how to remove it so I removed two of the four burner gaurds (not sure what they are called) and the flame sensor did have some corosion on it, I put everything back together and had a reading of 0.3 to 0.5 this time by testing terminal 8 but the furnace still didn't kick on. Can you give me some pointers on how to completly remove the fuel sensor? it almost looks like I have to remove the entire burner assembly.
 
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Old 10-29-12, 05:49 PM
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you may have to. Without being there I can't tell you for sure. Did you try it without testing? (put the lead back on terminal 8)
 
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Old 10-29-12, 05:54 PM
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That did it!!!!!!!!!!!!!!!! I tried it again and now I have flame and the furnace is burning and the blower is going. Thanks so much!!! I have been without heat for 4days and the repiair man I called with the symptoms said it was definately the gas valve and it would cost $475 for parts and labor to replace. Thanks again. If i can donate to you or the forum I would be happy to.
 
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Old 10-29-12, 05:57 PM
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Donate your personal skills back into the forum and help others. I'm glad it is working for you.
 
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Old 10-30-12, 07:44 AM
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Great! Ok so it worked for at least three hours last night then I got up this morning and it was doing the same thing. I giggled the connector on the gas valve while the pilot was lit just make sure the connections were Ok and that didn't help. Should I order a new flame sensor or should I remove the burner assembly so I can actually remove the entire flame sensor? Also if I should buy a new flame sensor is there a specific one for my model or are they universal. Thanks.
 
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Old 10-30-12, 09:31 AM
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Remove flame sensor and pilot Assyrian. Clean both and recheck.
 
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Old 10-30-12, 05:59 PM
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Well I removed the flame sensor and pilot assembly and thoroughly cleaned them both. The pilot assembly seemed fine and the flame sensor didn't seem too bad, but I don't really know what I'm looking for. I reassembeled everything and tested the flame sensor and it still showed around .2 to .4 to .5 micro amps DC. After running one cycle, the furnace lit up and ran for about 15 minutes then at some point shut off. I went back down stairs and turned the power switch off then back on and it cycled twice, after the third try the burner lit but the gas valve started making a very fast buzing sound very loudly(this didn't happen the first time it succesfully lit after taking the flame sensor out). The burners were still burning and I let it run for about two minutes then got a little nurvious and shut it off. Waited 5 minutes and turned it back on, the furnace tried to light twice (I heard a slight click I think from the ignition control module then a louder click from the gas valve and the pilot lit then after about 15 seconds(the main burner failed to light) another slight click followed by a loud click from the gas valve then the pilot burned out) then on the third time the burners lit and the gas valve started making the loud buzzing again. Is this a common problem and should I just let it run and see what happens? I'm 100% sure everything is back in order except there is a chance the flame sensor may not be in exactly the same position but I'm talking very very slight change.
 
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Old 10-30-12, 06:12 PM
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Half a microamp is too low to operate the furnace reliably. I would say that is the reason you are getting poor reliability.

Measure the AC voltage between the flame sensor and chassis ground and report that here. Look for any poor wiring connections.


Sounds like it's probably a bad circuit board not applying adequate voltage to the flame sensor, I'm guessing.
 
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Old 10-30-12, 06:48 PM
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I'm leaning towards SP's idea as well.... You may be due for a new ignition control. The good news if you go with the honeywell s8610u3009 replacement is that the new has diagnostic LED and weak flame signal indication.
 
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Old 10-30-12, 07:05 PM
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Thanks, just to clarify, I need to pull the flame sensor wire from the ignition control module and measure the voltage from the module to chassis ground?
 
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Old 10-30-12, 07:14 PM
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yes, that is correct.............
 
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Old 10-30-12, 07:43 PM
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Ok, I performed the test three times, I had results of 0.0 to .1 to .3 and once it got up to .5 and then several times it would go back to zero and when I was performing the test and getting readings other then zero on the meter, the ignition control module would make different clicking sounds then what I have heard it make before. Also. I made sure the pilot was lit while performing the test cause as soon as the gas valve would click I would always get a reading of zero. Also, in my post number 32 I mentioned the loud buzzing sound from the gas valve, the next time I turned the furnace on and it worked the buzzing was only very slight. Is it normal for the gas valve to buzz loudly or could that be a symptom of the faulty ignition module?
 
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Old 10-31-12, 12:31 AM
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What's the AC voltage being applied to the flame sensor?
 
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Old 11-02-12, 06:42 PM
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Well guys the furnace has been working for three days without a problem. I haven't done anything different since my last post but it just started working. I ordered a new ignition control module but I might end p sending it back. Thanks again for all the help!
 
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Old 11-02-12, 07:53 PM
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What is the DC microamps on the flame sensor now?

My suspicion is that you had a defect in the ignition module which was not applying adequate AC voltage to the flame sensor, which therefore couldn't produce an adequate flame rectification current to keep the burner lit.

The odds are that will recur.

So check the flame rectification current NOW to see what you currently have when the furnace is working properly. Also measure the AC voltage being applied to the flame sensor ----probably 24 VAC.

If it quits again you will be able to check the problem with greater confidence if you have these readings when the furnace is operating properly.

And I'd see how long you can hold onto that part and still return it for a refund. Having the part readily available may prove to be a comfort if the part fails again, as I suspect it will.

Failing parts rarely get better. They may operate intermittently for a while, but that's usually on their way to permanent failure.
 
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