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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22541
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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York P3HUD20N10401C gas furnace with White Rodgers 50A50-241

Customer Question

York P3HUD20N10401C gas furnace with White Rodgers 50A50-241 control board.
Last Wednesday furnace would not maintain flame, cleaned flame sensor with steel wool and furnace worked fine until sometime yesterday. Was out of house yesterday and apparently did not ignite and all furnace was doing was blowing cold air around, no heat cycle. Took front panel off of fan cabinet, which disconnected interlock safety switch and check control board for errors. No error codes flashing. Reinstalled fan cabinet panel, through power back on and furnace cycled properly into heat mode and maintained flame until thermostat temp reached.
Unfortunately I didn't get the panel 'hooked' just right and during the night the panel fell off getting system into a no power condition.
Reinstalled panel properly but now system does not want to cycle into heating mode; that is once panel is in place system immediately goes into full fan mode without flame. System never goes into per-heat mode where flue fan runs nor into heating ignintor.
Submitted: 7 years ago.
Category: HVAC
Expert:  BillyHvac replied 7 years ago.
Hello, if the panel fell off in mid cycle it may have tripped the limit. Behind the gas valve on the front wall is a rectangle flat plate with 2 wires attached. Turn power off and remove that switch, tap end a couple times, reinstall and power up. See what happens
Customer: replied 7 years ago.
We'll give it a tap-tap after dinner.
Expert:  BillyHvac replied 7 years ago.
I will leave this open
Customer: replied 7 years ago.
Tap Tap didn't work.
Expert:  BillyHvac replied 7 years ago.
I assume door is back on and switch depressed?
Customer: replied 7 years ago.
Yup, continuity on each side of the switch and when the switch is depressed we have a closed circuit.
Is there a weird chance this thing is going into lockout and we aren't properly unlocking it?
Expert:  BillyHvac replied 7 years ago.
If the circuit board is in the blower section, we want to tape the switch down. That way we can remove the door without erasing the fault code from the board
Customer: replied 7 years ago.
No problem. Give me a minute or two. I'll just hard wire across switch and insulate. BTW, there is a little peep hole in the panel and I can see the fault code light which is not flashing, completely dark. Code on board indicates that if light is NOT flashing, no problem so we have a fan running without flame and no code light flashes.
Expert:  BillyHvac replied 7 years ago.
so far we are heading bad circuit board..
Customer: replied 7 years ago.
Been Googling for manual for control board and finall found one as PDF. Says to get out of lockout need to interrupt call for heat MORE than 1 second but LESS THAN 20 seconds, anything else diverts board into automatic lockout which is one hour. Manual says that when lockout is detected gas valve is deenergized and blower is energized at heat speed.
If Board suffers internal failure, light is continuously on. System lockout is indicated by one flash then a pause, power on is indicated by one flash at power up. If 24v is interrupted for at least one second, auto reset can occurr but may also have to reset flame rollout sensor.
I'm going to power everything back up, reduce the thermostat to under house temp and then call for heat, turn thermostat back down under house temp for more about 10 seconds and see what happens.
Expert:  BillyHvac replied 7 years ago.
how did test go?
Customer: replied 7 years ago.
Turned both 120v and 24v power back on with thermostat set over room temp; i.e., calling for heat. Furnace went immediately into full blower mode. Turned all power off, set thermostat at room temp and powered back up, then reduced thermostat to under room temp for about 10-15 seconds, turned thermostat way up over room temp and wowow! proper furnace cylcing. Ran fine all night.
I'm positive that we got into lockout mode and with all my fiddling around never unlocked the control board.
Wonder why they don't put lockout info on control board along with trouble code.............grrrr....
Expert:  BillyHvac replied 7 years ago.

Well done...I agree with the reset info, but I have even found that process suspect. Thanks for your patience.

Customer: replied 7 years ago.
FUMBLE....unit stopped cycling around 1:30 this afternoon. Have spent the rest of the afternoon tracing wiring and circuits for continiuty.
What I found....sort of that there is a defective male pin on the control board. Vibration apparently causes loss of continuity between the male pin and the board causing an intermittent flame out. Why this beast went 4 days after cleaning the flame sensor without skipping a beat beats the devil out of me.
Today's tip came when once again I couldn't get the beast to cycle and out of frustration tried my old mechanics trick....gently tapped the control board and immediately went into ignition cycle but after a few minutes flamed out after the circulation blower came on.
Started wiggling the board and wiggling caused the unit to begin cycling and if you held the 12 pin connector just right the unit would run extended minutes.
The down control boards in Iowa until tomorrow morning.
Expert:  BillyHvac replied 7 years ago.
A trick I have down with these is to take a rubber band and flex the circuit board and stretch to something secure so it gently warps the board a bit. Just to buy time...
Customer: replied 7 years ago.
Let me give it a try. I got a little piece of wood I can 'bend' around. From what I can see, the pin has broken free or cracked free from where it enters the board.
Don't you just love intermittent problems....test of your skill and patience..........
I worked my way through college in the early 1970's turning wrenches on autos. Never was happy just replacing parts to solve something...tried to out-think the problem.
You've been patient with me....I'll let you know how this comes out.
Expert:  BillyHvac replied 7 years ago.
Keep me posted....
Customer: replied 7 years ago.
Gotta remove this &*^%$ board once again. We are getting on a first name basis....not always friendly.
Expert:  BillyHvac replied 7 years ago.
It just make you appreciate the fix all the more.
Customer: replied 7 years ago.
Grrrr....can't seem to get it to bend just right. New board arrives in AM.
Expert:  BillyHvac replied 7 years ago.
Good luck and let me know
Customer: replied 7 years ago.
Never could get board warped to make consistent contact.
Should have new board in an hour or two.
Expert:  BillyHvac replied 7 years ago.

Rats....keep me posted

Customer: replied 7 years ago.
Got the new board in Des Moines finally after lunch and stuck in the furnace and we haen't missed a lick since then even through 16" of snow and 60mph wind. Think the problem is solved.
Expert:  BillyHvac replied 7 years ago.
Very good! Thank you for the follow up.....stay warm and be careful