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Discussion Starter #1 (Edited)
I have a ComfortMaker RPJ II gas furnace with a light blinking 6 times when it tries to startup. I'm trying to figure out what likely needs to be replaced. It was installed in 1993. The furnace doesn't start whenever the light is on, but the furnace has started enough times (when the light was not blinking) to where it has kept the house warm this past week. Yesterday I tried to sand down the flame sensor and its electric terminal with emery cloth and it didn't appear to fix the issue. In fact, the unit started one last time after that and now its completely locked out. I've tried to kill power to the unit and reset it. If I wait only a few minutes before restarting the unit's 50A50-110 control will make some clicking noises and then go straight to the blinking light without trying to light the furnace. I left the power off overnight to the furnace and this morning it did go through the furnace lighting sequence, but it still just lit the 3 burners and then shutdown and showed the 6 blinking lights for a single time and then locked out without trying the furnace lighting sequence again. I'm interested in getting people's opinion of what the issue is and what likely needs to be replaced. There have been a few different posting that seem similar. Most focused on the flame sensor and just sanding it down, which again didn't seem to work for me. I'll attempt to add some video links or pictures of the furnace in action later on, especially if I get it to try starting again. Also, I've listed the furnace specifications below.

Furnace Brand: ComfortMaker RPJ II
Model number: GUI075A012AIN
Manufacturing Number: GUI075AEAIN
Control Board / Circuit Board / Furnace Control Module Number: 50A50-110
 

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Discussion Starter #2
Just another question on this item. If you think a control board replacement is needed, let me know if you think a homeowner could do that on their own or if a HVAC technician is required. Is their something else required whenever a control board replacement is done such as some type of setup process?
 

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They're easy to replace, just need to follow the instruction sheet, and do it wire for wire.
 

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Sounds like the restricter disc on the inducer might have failed
 

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Discussion Starter #5
Here's some videos of the errors I'm finding. The first link is what I get what I turn off electricity to the furnace overnight and then turn it on. The 2nd video is what I get when I then turn off the unit once more and then wait a few seconds to turn it back on again. Again, let me know if you know what the problem is.

1st Error Message:
2nd Error Message:
 

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Discussion Starter #7
It doesn't say on the furnace. The label on the furnace shows errors for the light blinking 1 to 5 times. It doesn't list a reason for blinking 6 times.
 

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Discussion Starter #10 (Edited)
To Done_That,
I'd be interested in knowing where you found that fault code? Do you have a similar furnace or did you see that on some other product documentation for this same furnace? For reference, here is a listing of the error codes shown on the label of my furnace. Also, I'm sharing the link of the label on my furnace. These codes match what is in the manual as well.

Also, I've gone ahead and ordered a replacement flame sensor and control. For future reference to others with similar furnaces, the original parts (White Rodgers 760-470 and 50A50-110) are now obsolete at White Rodgers. I found a replacement ComfortMaker 1380687 flame sensor online. For the control board, I was told to get part number White Rodgers 50A55-843. Once they arrive I'll share if they made any improvement.

1 flash - system lockout due to retry
2 flashes - pressure switch contacts closed
3 flashes - pressure switch contacts open
4 flashes - open high limit switch
5 flashes - open rollout switch
continuous flash - flame sensed with no call for heat

Link to Label with Error Codes:
https://flic.kr/p/AZjbGW
 

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I work at W-R. I pulled the obsolete documentation and found code 6 was added in
~ April '93 as a running change to the existing board...so some did not have it, and later boards did.

Pretty common that software gets changed on a control over time. Perhaps the original board had already failed at some point and a newer version replacement was put in. Very possible on a furnace of that vintage.
 

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Discussion Starter #12
To Done_That,
Thanks for your help. I also called White Rodgers technical support and got the same error code reading of "shorted flame sensor probe or water level sensor" that you provided for 6 flashing lights. Since this is a 80+ furnace it seems there shouldn't be any water level sensor on this furnace so it may narrow it down to just the shorted flame sensor. Again, I'll report on what happens with the replacement parts when I receive them.
 

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Flame sensors have known to go bad.

Try replacing the flame sensor and if that doesn't fix it replace the control board
 

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Discussion Starter #14 (Edited)
I first tried to replace just the flame sensor with a newer one and it did not work for me when using the older 50A50-110 control. I wanted to note that the new flame sensor I got was much longer than the original one on my machine. See the attached picture for a comparison.
It appears that White-Rodgers didn't offer a replacement part so I had to order a replacement by referencing the Goodman part number for the flame sensor which was 1380687. I presume Goodman switched to a different manufacturer other than White Rodgers for the flame sensor at some time. By the way, I ordered the replacement flame sensor through Amazon. Anyway, what fixed the problem for me was to switch the control to the newer White Rodgers 50a55-843 control. It was able to work even with the newer flame sensor I had bought. Its been working for at least a full week or two now. What helped me in transferring the wires was to a) label the wires before moving them b) transfer one wire at a time c) use a needle nose pliers to remove the terminals from older control d) pulling the female terminals by the insulation cap and not by the wire itself. I'm keeping the old flame sensor as a backup. It would have been a pretty quick job to fix for most people, but I like to take my time on something I'm not that familiar with. Thanks for everyone's help.
 
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