Carrier Weathermaker, Gas Furnace - Intermittent Ignition
Carrier Weathermaker 8000 - Model #: 58WAV090-GC (circa 1992) For the last 3 seasons, my no ignition problem was solved by cleaning the flame sensor. This year, not so much. Sequence: - Power switch ON, blower motor runs for 20 seconds and stops - Draft Inducer motor starts - small click, Hot Surface Ignitor (HSI) Glows - click, HSI powers down with no ignition The inducer motor stays running and the HSI repeats it's process 4 or 5 times and then the inducer motor shuts down and system goes dormant. I believe that the gas valve never opens. The resistance on the HSI reads 88.7 -- the thresholds I found OL says between 50 and 90 is acceptable. When I disconnect the flame sensor and power up, the process is exactly the same. I think (hope) that the culprit is the flame sensor but I know they don't go bad very often. I'm not sure if I can test it's low voltage with my very basic multimeter. Today, the furnace would not fire up even after I cleaned the flame sensor. At a loss for a solution and while trying to figure out if the gas valve was opening, I hit the flame sensor briefly with a propane torch during the start up sequence/while the HSI was glowing and presto, it fired. It has been igniting on it's own each time the t-stat calls for heat for the past few hours. I'm lost. What should happen: The thermostat is turned up The inducer motor turns on. The HSI gets white hot The gas valve turns on the gas and the burners light The fan turns on to circulate heat around the house. Measure the voltage across the gas valve when the HSI heats up and you hear the click. You should get 24 VAC across the gas valve for 3-5 seconds even if the burners don't light.
Sounds like you have an intermittent problem and you jogged it into working normally again. You can expect it to quit again, and you can perform the tests described above. I would call it turning on when you hit the flame sensor with a torch a coincidence. I take it you found that the gas was NOT turning on until you had this bit of good fortune. the PAV and WAV both use the same circuit board they made about 5 different versions of this circuit board (and more)? to date HK42FZ is the part number If it's never been changed, you may consider replacing it if it's really 20 years old agree with everything SeattlePioneer said what fault code have you been getting weird codes may mean the board needs to be changed Thanks SeattlePioneer. Yeah, I don't think the gas ever turned on when it didn't fire up. I'll check for 24 VAC across the gas valve for 3-5 seconds -- I'm assuming I should wait until the 'no ignition' problem begins again, right? And to do that, I would probe the brown and the blue wires pictured, correct? Where should the meter be set and which lead to which wire? Thanks again! Hey B, thanks for responding. No codes on this unit as there is no led light anywhere. Well, none that I see anyway. And I took the cover off the board and looked hard. Thanks for the part number! You need to check the board for a fault code system? Is there a sight glass on the bottom door of the furnace? the last version of the HK board was a HK42FZ011 I think the new numbers are different, haven't sold one in a while Nope, no peep hole. Took off the cover and then a second small cover with 2 screws that covers the circuit board -- no LEDS or blinking lights anywhere? What's an HK board? Is that the one my furnace uses? So, what I'll need is going to be the HK42FZ011 and not the HK42FZ? Thanks again B-nut! Where should I buy that and what's a good price? they made HK42FZ001 003 005 007 009 011 and so on as each series of board was upgraded see if you can find a part number on the board Closest thing resembling a part number is CES 0110057-00. Make sense? Okay, so you have a way early version So the CES board is replaced with the CES011005702 The new board will have a fault code chart and red flashing light the board you have has no fault code system make sure the screws holding the board in the control panel are tight otherwise you get a weak flame signal Cool. A quick search online I saw it for $129.26. Does that sound about right? Also, I should have mentioned that central AC is part of this system as well. I assume it was retro-fitted to the existing heating system at some point -- but it was that way when I bought the house 15 years ago. Does that change anything for my upcoming troubleshooting battery of tests? :dontknow: you need to see if you're getting 24V ac across the gas control when it clicks to come on C and P terminals Do that now, even though at this time, it is working correctly? And, where should the meter be set and which lead to which wire? Thanks again, again. If it's working it's an intermittent problem...maybe a new board will help you trouble shoot, eh? Yep, intermittent. Not sure about the board just yet. I think I need to take it down the battery of tests like Seattle is suggesting once it quits again. But yeah, if 20 years is the typical life of a circuit board, I expect I'll be doing it soon enough. Before, I was hoping the problem wouldn't come back, now, I can't wait until it does!! And, where should the meter be set and which lead to which wire? You are measuring AC so it doesn't make a difference which lead goes to which terminal. You should be using the AC VOLT scale just over 24 volts. Some meters it's 50v some it's 100 v. You are measuring AC so it doesn't make a difference which lead goes to which terminal. You should be using the AC VOLT scale just over 24 volts. Some meters it's 50v some it's 100 v. Got it PJ, thanks! My multimeter is a cheapo -- in the ACV section, it has only selections for 750 and 200. But I also have an old-school analog meter that has selections for both 50V and 100V. I'll figure it out. I appreciate your help. Even the 200 volt choice should have a scale that would allow you to verify 24 VAC and 120 VAC would be easy. The 200 setting should do it, right? It's 0-200 -- right? Here's the one I have: Yes --- use the 200 ACV setting, which will have ample sensitivity for 24 or 120 volts. Connect one test lead to COM at the bottom and the other at the connection just above it, which alloows measurement of volts, resistance and milliamps. It looks like it has a 200 uamp scale as well. 1 milliamp = 1/1000 amp 1 uamp= 1/1,000,000 amp But you may not need to measure that anyway. Thanks Seattle for that clarification. All is quiet here as the furnace has been re-firing on it's own, several times per hour, for the past 24 hours. But like you said, failure is inevitable. When it does, it will be panic time all over again. I'm all set up to measure for 24 VAC across the gas valve when the HSI heats up. Can you (or anyone) advise or link me to what my next step in testing should be so that I'm ready and can report back with the proper data when the failure occurs? Much thanks to all. Well, it's over 2 months later, through the thick of winter and with my multimeter close-by, ready to test for 24 volts, the damn thing hasn't failed again. In case someone with the same furnace Googles their way into this thread I've done 2 things (and I'm not claiming this is a fix as I fully expect it to fail again at some point but for now, it's working): 1) I cleaned the all of the spade connectors, including the jumper, on the gas valve. 2) I opened the vents for an unused room in the house that had previously been shut down. (I had read here that shutting down rooms can cause excessive heat inside the furnace and sometimes prevent ignition). That's it. It just now failed to ignite again. I tested and have 23 volts at the valve. Bad valve? Replace? Sounds like you need a new valve. Thanks Houston. My readings were consistently 23.0 VAC and 23.3 VAC with several tries - never actually got to 24 VAC. If the valve was good, that'd be enough to open it, right? That meter could be off by 1 volt. I had intermittent operation from a gas valve last Monday night. Ended up replacing it. It is much easier to diagnose a problem that is consistent. Thanks again. My intermittent problem has become consistent for the last 18 hours -- I keep re-setting the furnace but it won't fire. I think the valve finally took a sh*t. So, I think we can say now with a fair amount of certainty that the problem is -- and always was -- the valve. I really appreciate your help. I'm happy to help. Looks like SP had this figured out in his first post. Conclusion: My local supply house did not have my valve in stock -- but did have a valve that was identical in appearance to the old one, although the model number was different. It appeared to be used but the supply house owner could not remember where it came from -- only that it's been hanging around here for years. He sold it to me for the price of a used unit ($50) and guaranteed it. He stated, if you have any problems, just let me know. I felt satisfied. The hypothesis on the valve was that it was used to troubleshoot a system -- found not to be the culprit and returned. The owner is very accommodating with his customers like that, so this hunch very likely. It fired right up first try! So, we're up and running!!! I'm glad to (hopefully) finally have a solution to this dilemma that has dragged on for a long time. If anyone has any input on the potential woes of using a valve that is exact in appearance yet has a different model number, please advise. Thanks for your help!
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