York P3HUD20N10401C Furnace not properly cycling

[rddmar]

Of course on Thanksgiving York P3HUD20N10401C furnace wouldn't heat. Furnace would not maintain flame so cleaned flame sensor and seemed to work O.K. for next few days. In trouble shooting did take off front fan compartment panel and apparently when reinstalling fan compartment panel didn't get it 'locked' in place. Last night the panel fell off opening the safety switch prohibiting furnace from operating. After properly reinstalling fan compartment panel, furnace wants to immediately go into what I call full fan mode; i.e, furnace doesn't not want to go through purge, ignition and heating cycle, just starts back up in full fan with no burner operation.

Did the system go into lockout and if so, how do we get it back out of lockout? Has a White Rodgers 50A50-241 control board showing NO faults.

Thanks

[ACtechGUY]

I am not real familiar with york furnaces , but I can tell you that several high end furnaces have all kinds of operational quirks. I think you make be seeing one of those quirks. When power is restored to some furnaces and the theremostat is calling for heat at that moment, They will go into a safety time delay mode that usually brings on the blower and lasts at least 5 min (very annoying too I might add).

To prevent this from happening just turn off the thermostat and restore power to unit. then turn themostat to heat. It should go into a normal heat cycle. Or you can just wait out the time delay.

[rddmar]

Thanks for the try. Furnace has been powered off for over 2 hours along with the thermostat both 'off' and below the room temp. Just tried cycling the system back on with thermostat on first, then furnace power, then increasing thermostat above room temp. Furnace responded a few minutes later by going into full fan mode, no burner.

[ACtechGUY]

Check that the draft inducer motor spins. If it is locked up or burnt out or the control board is not sending the 110volts , what you described will happen.

If the draft inducer proving switch does not close after a certain period , the ignitor will not do anything and the furnace will likely bring on the blower.

[rddmar]

Draft inducer motor spins manually. I took out flame sensor and re-cleaned it once again with steel wool and we seem to have proper ignition. I'm beginning to think I have a flame sensor acting more than weirdly....new one on the way.

[ACtechGUY]

Only one problem with the flame sensor route.... If you don't have a flame to start off with then the problem can't possibly be the sensor. The flame sensor is just a metal rod. I can't think of why it could ever be bad. Just bad connections. It most definitly would not keep the inducer fan from running like it should.

This is the link to the control board instruction / operational info.

http://www.white-rodgers.com/wrdhom/pdfs/instruction_sheets/0037-6265.pdf

The paperwork indicates that the board is going into lockout mode.

[rddmar]

Hmmm...#1 on the lockout is interesting....have to interrupt call for heat for MORE than 1 second but LESS THAN 20 seconds. I've interrupted for way more than 20 seconds........... but have actually had the system power off for over an hour along with the 24v off for more than an hour. Gonna try a 10-15 second interrupt and see what happens.

[ACtechGUY]

I would take apart / check all connections to and from the control board . There is a 4 pin connector that sends 110 volts to the draft inducer and 110 to ignitor.. check for 110volts to inducer at connector with a call for heat. if no voltage with heat call then board is bad.

Also reseting the control is a simple matter of cycling 110 power to the heater. trying to reset a lockout by manipulating the thermostat just confuses things and can lead you down an incorrect road of troubleshooting.

[Budget Appliance Repair]

Have you checked for the simple thing?

Maybe in trying to get it to go you switched the Fan switch, (on the wall t-stat), from Auto to On, which would make the blower fan run continuously anytime the t-tstat is in any ON setting, (Cool or Heat).

[rddmar]

TOUCHDOWN!

Thanks for the manual on the control board!

The problem indeed was the lockout mode; all of my fiddling was keeping the system in lockout which keeps the fan blowing as if at heat mode. This particular board needs to be reset by dropping the call for heat more than 1 second but less than 20 seconds; any other length of time keeps the system in lockout.

Furnace ran perfectly during the night....thankfully since we went from the mid-60's in Iowa yesterday to low 30's this AM.

[rddmar]

FUMBLE!

Furnace stopped cycling around 1pm today with new flame sensor.

After exhaustive tracing of wiring....can't believe how many circuits can get involved...found of all things a bad pin on one of the 11 active male pins on the control board. Since the control board is mounted to the squirrel cage, when the fan engages it slightly shakes the board causing loss of continuity in the power circuit, stopping the flame and sending the unit apparently into locked mode. If you tug slightly on the 12 pin wiring connector going into the control board, the unit will say lit for an extended period...several minutes. Once you let go or the vibration move the contact between the male and female pin, loss of flame and into lock out.

Defective control board that is throwing absolutely no error codes probably since it is a mechanical failure, not electronic.

No control board available in Iowa until tomorrow....anyone know how to hard wire this beast for a surge of heat???

[ACtechGUY]

You may want to try duct tape or somthing like it to put tension on the connector to keep things going.

You could also remove the board and check the back to see if there is anything that can be soldered back into place. many failures are due do a solder trace on the board braking / burning up or the relays on the boards will often get hot enough to melt off the solder.

Good luck