York Gas Auxiliary Heat Not Working

York HVAC Model # GY9S100C16DH11K

The gas auxiliary heat is not working. Heat pump heat works fine. Any help diagnosing my problem is greatly appriciated.

It finally got cold here a few days ago and my heater was just blowing cold air when I woke up in the morning. Found it with the control board LED doing 7 red flashes. I checked the gas line, shut the power off, turned it back on and the auxiliary heat fired up just fine. I thought it was fixed.

Then last night it got cold again and the auxiliary heat didn’t kick in (7 red flashes on the LED). Tried the same routine I had done before but it didn’t work. Started reading through the forums here to see if I could diagnose the problem but still can’t get it to work. The gas is turned on and other gas appliances in the house work fine, including an on-demand hot water heat right next to the furnace.

Here is what it is doing right now:
When the furnace has been turned off (at the circuit breaker) and turned back on, the control board LED starts with a slow green flash, then changes to slow amber flash (call for heat). The call for heat is accompanied by a few clicks from, I believe, the control board. The combustion ventilation fan turns on. The igniter starts to heat up. After about 25 sec, the igniter is bright orange and there is more clicking and the igniter turns off. It cools down for about 15 seconds and then turns on and off 2 more times in about the same time sequence. At no time do I hear or fell the gas valve turn on or off. I also don’t hear any gas hissing. There is never any gas flame. After the furnace goes through the three tries to ignite, the LED starts blinking red 7 times and the furnace starts blowing cold air.


This is what I have tried so far:
• I lightly scrubbed the flame sensor, which didn’t have much buildup on it.
• Turned off the gas, disconnected the gas line from the furnace and checked to make sure a little gas came out when I cracked the valve open. Gas came out. (According to my son, “It stinks!”)
• Checked to make sure the gas valve switch was in the “on” position.
• Checked the OHMs on the igniter – 55 OHMs
• Checked the OHMS on the Gas Valve – 15K OHMs
• Checked for voltage to the gas valve: it’s getting about 24volts for 6 seconds right about the time the igniter is being turned off


My best guess is the gas valve is bad.

Anyone have any ideas on what is wrong?

Thanks for reading. Any help is appreciated.

 

Welcome to the forums!! Based on your testing and the fact you have 24V at the gas valve for the 6 seconds it appears your gas valve is bad. With 24V to the valve, gas should flow. You might try to press down and wiggle the connector where the wires attach to the gas valve while calling for heat.