York Furnace problem

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Old 05-04-19, 03:55 PM
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York Furnace problem

Hello, I have problems with my furnace.

It is York G8C model and model number is G8c07516muc12g. I have been using this furnace for about 15 years now.
I’ve had a problem with this furnace about 7 years ago, and it was repaired by replacing circuit board.

New problem started from about three weeks ago. Furnace stopped working and there was error sign on the board. 3 red blinking flashes - Pressure switch failed to close.

I restarted the furnace and found that ignition didn’t start at all after inducer pan started to operate.
3 flashes appeared after several clicking sounds and furnace stopped operating in few minutes.

So I tried
- turned off the power
- Cleaned up the inside of furnace.
- Checked and replaced the air filter.
- Checked the pressure switch tube and cleaned inside.
- unplugged the pressure switch wires and plugged it back.
- used paperclip to clean the nipple on the inducer pan
- checked the ignitor (it looked bit dirty.)
- There is no condensate pipe for my furnace, so I cannot check clogged pipe.

Nothing worked. Based on technician's advice, I ordered new pressure switch and ignitor, and replaced them.

OK it started to work again after trying resetting the furnace several times, but it lasted only for 2 days and stopped working again.

This time the error sign was 4 flashes - limit switch open.

I turned off the furnace, cooled down, restarted, and it didn't even start to ignite it and showed limit switch error sign. After that, it just blowed cold air for several minutes and stopped operating.

Strange thing is that if I unplug all the wires on the circuit board, reconnect them and restart the furnace, then it starts to ignite the flame and run normal for 5 to 10 minutes. After then, Fire's gone, 4 flashes appear, and it starts to blow only cold air. If I let it go, it will stop operating eventually, and tries to restart after couple minutes, but it doesn't even start ignition by itself. The only way I can start to fire up is unplug the wire, reconnect them back to the circuit board and restart it. Then it runs for about 10 minutes, fire disappears, 4 flashes error and blows only cold air.

I tried to clean the flame sensor with steel wool, but it didn’t fix the issue.

Now it even stopped making fire at all.

Current symptom is that it shows random 3 (Pressure switch failed to close) or 4 flashes (Limit switch open).

If I power on the furnace, it starts with green flash (normal status), inducer motor starts, flash changes to orange light with slow blinking (sign when it is normally operating), ignitor starts to glow, can hear clicking sounds several times, but it doesn’t start fire up, ignitor stopped glowing, and orange light changes to red error blinking flashes. 3 or 4 flashes randomly. Rarely, it shows 6 flashes as well.

Or

It just starts to show 3 or 4 flashes right after I power on the furnace. In this case, there is no ignitor glowing at all.

I checked a limit switch and 3 roll out switches with multimeter, it all showed closed status when power is off. I also tested pressure switch with multimeter. Pressure switch was opened status when there is no pressure, and it closed when the inducer motor starts blowing. I don’t know any other way to test the switches now.

I tried to bypass the limit switch for testing, and fire started. So I replaced the limit switch, but it doesn’t fix the problem. Same 3 or 4 flashes.

Do you think it might be a circuit board problem?

Thank you so much in advance.
 

Last edited by infinitespace; 05-04-19 at 04:15 PM.
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Old 05-04-19, 09:55 PM
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Get a can of contact cleaner. Pull the 12 pin plug off the control board. Spray the pins in the plug with the cleaner. Give it one shake to remove excess liquid. Reinstall it and remove it several times. Try the furnace. If it's still acting up... spray the plug again. Don't spray into the control board. The fluid will transfer and clean the pins during the plugging in.

You can load the manual for your furnace from here...... York G8C manual
 
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Old 05-04-19, 11:34 PM
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Thank you PJMax. I will get the contact cleaner and try it tomorrow.
 
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Old 05-05-19, 09:53 PM
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OK, I tried to clean the plugs with the contact cleaner several times, but it didn't work.

Current symptom - When I power on the furnace, it starts inducer motor, ignitor starts to glow, two times clicking sounds, but no flame starts and ignitor stops glowing, 3 flashes appears - pressure switch failed to close.

For the testing purpose, I tried change the new pressure switch to old pressure switch, and started the furnace. And then, the air blower motor(I don't know what it called exactly) started to blow cold air like it is trying to cool down, and 4 flashes (limit switch open) appears immediately. No 3 flashes, no ignitor glowing, and no normal inducer motor starting process. If I swap the old one to new one again, the problem come back to the above symptom.

Is that the pressure switch problem? Is there any way to test if the new switch function properly with multimeter? Should I replace the flame sensor? or Is that circuit board problem like 7 years ago?

Thank you all for the help.
 
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Old 05-06-19, 12:12 PM
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I had you clean that plug due to the unrelated faults you were getting. All the limits are on that plug.

When you call for heat...... the inducer starts and the pressure switch must close. If it doesn't close..... the igniter will not heat. You're saying the igniter is heating and when the gas valve should be opening you are getting an interruption and then three flashes (open pressure switch). That's telling me there is a board problem.

You can watch the pressure switch. Put your two probes directly on the wires. There should be 24vAC measured. When the inducer starts..... that should drop to 0v and stay at 0v. If that does stay at 0v and you get a pressure switch fault..... the board is most likely the problem.
 
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Old 05-07-19, 10:52 PM
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Thank you for the advice PJmax.

So I tried to check the vAC by multimeter several times because the symptoms change randomly.

I powered the furnace on. It stayed as idle status with green flash light since the indoor temperature is higher than setting temperature. I unplugged pressure switch wires and checked the vAC. It showed 0.1~ 0.2 vAC during idle status. I connected wires back to the switch bit more than half way and tried to touch the terminals of the switch by the multimeter probes. I set the temperature higher from thermometer to turn the heater on.

And here are 3 major symptoms.

1. Inducer motor started, and the vAC changed up to 4.4 vAC for about 1~2 seconds, and came back to 0 vAC. Ignitor started glowing, and fired up. It ran normally. (It's been a week since I had seen the fire last time)

2. I turned on the heater. Inducer motor started, and vAC changed up to 4.4 vAC for about 1~2 seconds, and came back to 0vAC. Ignitor didn't start glowing, 3 flashes appeared and furnace stopped operating after about a minute.

3. I turned on the heater. 4 flashes appeared immediately, and vAC didn't change at all but stayed as 0vAC. Air blow motor started, and blowed cold air. (same as the previous reply)

OK, so what could be the next step I can try with this furnce? Do you think I should try replacing the circuit board? or maybe flame sensor?

Thank you so much for your help.
 
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