Geothermal: No Heat / No Cool
Re: Contactor Won't Energize - No Fault Codes
The customers reports "No Cool" or "No Heat". Upon inspection you find that the contactor is not pulled-in and there are no fault codes from the CXM board (steady green light).
| Qty |
Possible Causes |
| 5 |
Bad CXM Board |
| 0 |
Bad Contactor |
| 1 |
No Call from Thermostat |
| 0 |
No Line Voltage |
| 0 |
Blown Low Voltage Fuse |
CHECKOUT:
1. Check Power
- Check for 230VAC at contactor inlet.
- No Power --> Check for Electrical Short-to-Ground & Check Breaker.
- Check for 24VAC across R & C on low voltage terminal strip.
- No Power --> Check the Low Voltage Mini-Breaker on transformer.
- Tripped --> Check for a Low Voltage Short
- Be especially cautious of low voltage wires pinched by control door.
- Check Green status light on CXM (tan) board.
- Green light Off = No Power or Bad CXM Board
- Green light On Steady = Normal Operation
- Green light Flashing = Fault Present --> Short TEST pins to display current fault code.
2. Check Unit Status
- Set the thermostat to call for heat or cool operation.
- Check for 24VAC between "Y" and "C" on the Green control board.
- No Power = No Call from the Thermostat --> Check Thermostat
- Check for 24VAC between "Y" and "C" on the CXM (Tan) control board.
- No Power --> Check wiring between control boards
- Power = Unit should start within 5 minutes.
- Check the control board for active Diagnostics.
- LED Flashing = Control in Lockout due to active diagnostic --> Short TEST pins to show diagnostic code.
3. Check Contactor
- Check for 24VAC across the coil of the contactor.
- No Power = Bad CXM Board
- Power Present but Not Pulled-In = Bad Contactor