Flame Fault error for Weil-Mclain WM97+

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  #1  
Old 02-10-18, 10:39 PM
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Flame Fault error for Weil-Mclain WM97+

I have a Weil-Mclain WM97+ 155 boiler/furnace. It gave me a lot of troubles recently. The main problem that I am facing is it gives me "Flame Fault" error from time to time. Based on the manual, that error means there are flames detected when it shouldn't, and the possible reason is the gas valve could not close properly.

When I first saw this error, I checked for flames through the observation window, no flames spotted. Then, I reset the boiler and it ran with no problem. one or two hours later, I found that the error come up again. I checked again, no flame, then reset, hours later, same error. I sat next to the boiler for a while and watched it finishing a few full cycles (presurge, fire, postsurge...). Moments later, I witness the error happening. After the boiler finished the heating request, it closed the gas valve and entering the postsurge stage. But on the display, it shows it detected weak flame signal. I checked the burner, no flames in visual. I even disconnected the connecting wire between the flame igniter/sensor (they are the same thing for this boiler) and the display still shows some reading for flame. Then it lockout and shows error "Flame Fault". I reset it immediately, but it still shows readings jumping (4, 8, 16, 40, 4, etc.). I tired to see what's the current between the control board to the flame rod with a multimeter. The moment I connect the connecter to ground with my multimeter, the reading goes to 0.

Right now, I have to keep resetting it since I don't know what's going on. Does anyone have any idea about what's going on here? Is that indicates I have a faulty control board? I checked online for the control board, it turns out Weil-Mclain does not want me to replace the board only, I have to purchase the entire control unit assembly (including display etc) at 800 bucks, so I really want to exhaust all other possibilities first.
 
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Old 02-10-18, 11:21 PM
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Welcome to the forums.

It sounds like you have a spark ignition system where the igniter and flame sensor are the same rod. On that type of system you can't measure the flame sensor current without using a special test jig. The igniter uses high voltage ignition which will damage a meter if you have it connected during ignition.

Pull the igniter rod out and clean it with a Scotchbrite pad or steel wool. It gets a coating on it that insulates it from the flame. It also must be engulfed in the flame during burner operation.
 
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Old 02-11-18, 07:48 AM
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Can anybody help me out here
 
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Old 03-06-18, 08:12 PM
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Thank you for your reply. Yes, I do have a system which using a combined igniter. When I connected the igniter rod, the flame signal went to zero, then I disconnected the multimeter and the reading will stay at 0 and the boiler will start fine. Does anyone have any idea about what's going on?
 
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Old 03-06-18, 10:48 PM
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When you measure for flame current.... the meter goes in series with the lead and set to the ua scale. You don't check to ground. On your system there is a high voltage sent thru the same wire for ignition. If your meter is inline during ignition it will be damaged.

I don't know that boiler so I can't offer much more help. The link below is the service manual.
Weil-mclain/default/files/field-file/wm97-ct-manual_1.pdf
 
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Old 03-12-18, 08:18 PM
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Ok, let me reshape my question to "What will cause a flame fault?" In my case in particular, why the flame signal jump up and down when there is no flame?

As far as know, the control board sends AC to the flame rod. Since flame is a kind of conductor, it will transform AC to DC. When the control board senses DC, it knows there is a flame. In my case, the control boards senses some DC current from somewhere other than the actual flame, what can cause this issue to happen? I said when i touch the connector and connected it to ground (then remove it right away), the boiler would start to operate normally, is that because i released the current away?
 
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Old 03-12-18, 10:06 PM
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Can you disconnect the flame sensor/igniter from the control board ?
If so... do you still get the random flame sense readings ?
If yes.... that would have to point to a problem on the control board.
 
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Old 03-14-18, 05:43 AM
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Wm97+

Have you had a proper combustion analysis and burner chamber inspection done? It is possible the boiler is burning too hot and the residual heat is tricking the flame sensor/ignitor as per the manual..
 
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Old 03-14-18, 11:00 AM
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Yes I tried to disconnect, and yes, i still had readings.

Just a month ago, the reading will not disappear no matter what i do, restart the furnace, disconnect cable etc.

Recently, the reading won't last that long, a couple seconds or so, it will go to 0. The boiler can now run for days without a problem before it gave the error. Since the error appears randomly right now, I am not able to catch it when the error occurs and try to disconnect it.

I do think it is related to the control board tho, I am wondering if I can repair it rather than replace the whole unit. The whole unit will costs me a thousand bucks to buy
 
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Old 03-14-18, 11:35 AM
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If you get an indication of flame with the wiring disconnected..... the problem is on the board.

There is 0 service information on that board. You will not find any board schematic as it's highly proprietary.
 
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Old 07-02-18, 08:47 PM
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Problem solved

My problem was solved it was due to some strange, but common reason (at least to this model). I think i couldn't find anything related to it online, i guess i'd better share it here so the others won't have to go through the whole process.

The problem is caused by a MELTED BURNER GASKET. I was told that there is a design flaw which cause the gasket to melt after using it for a while. When it melts, it fails to let that part of the boiler grounded properly (that's what i've been told. No idea why that will affect my flame signals). The solution just go online and find the gasket and replace it. If you are in the States, you are luck, since there are plenty of website that selling parts. But if you are in Canada, you can still buy them online but pay 60 US for shipping for the 10 bucks part, or you can contact your favorite heading company which may cause you 400 CAD.
 
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