York Gas Furnace: TG9S/GY9S
Re: No Light on Control Board
The LED light on the furnace control board indicates the status of the furnace.
In this condition, the light is constantly off.
Qty |
Possible Causes: |
|
No Line Voltage |
1 |
Blown Low Voltage Fuse |
|
Blown High Voltage Fuse |
|
Bad Transformer |
|
Door Switch Open |
|
Bad Control Board |
CHECKOUT:
1. Check Low Voltage
- Check for 24VAC between "R" and "C" on the control board LTB.
- Check for 24VAC across the output of the transformer.
- No Power Present → Step 2. Check Line Voltage
- Power on Transformer + No Power on "R" ⇒ Check Low Voltage Fuse
- Fuse OK = Bad Control Board
- Fuse Blown ⇒ Test for Low Voltage Short
2. Check Line Voltage
- Check for 120VAC on the inlet side of the transformer.
- Inlet Voltage Present + No Low Voltage = Bad Transformer
- No Inlet Voltage ⇒ Make sure the blower door switch is closed.
- Check for 120VAC on the line voltage wires entering the furnace.
- No Voltage Present ⇒ Check the following:
- SSU Switch
- SSU Fuse
- Breaker
3. Check Control Board
- Place a jumper between "R" and "G" ⇒ Check if the fan motor starts.
- Place a jumper between "R" and "W" ⇒ Check if an ignition sequence starts.
- No Operation = Bad Control Board
- Fan and Ignition Starts = Bad LED on Control Board