Goodman air conditioner thermostat or wall control displays E0 and system will not run

Safety first: Turn off power to the air handler/furnace and outdoor condenser at the breaker and service disconnect before removing any panels. Use a non-contact voltage tester to confirm power is off.

Steps to check and correct:

• 1. Inspect thermostat wiring: Remove the thermostat from its base. Verify each conductor is firmly landed on the correct terminals (R to R, C to C, Y to Y, G to G, W to W or W1/W2 as applicable). Tighten any loose screws.
• 2. Check cable condition: Follow the thermostat cable back toward the air handler. Look for staples through the cable, rodent damage, or crushed sections. If the cable jacket is cut or wires are exposed, the cable should be replaced.
• 3. Verify connections at indoor control board: Remove the blower door on the Goodman air handler or furnace. Locate the low-voltage terminal strip on the control board. Confirm all thermostat wires are secure and not shorting against the cabinet or each other.
• 4. Power cycle: Restore power at the breaker, wait 2–3 minutes, then reattach the thermostat to its base. See if the E0 code clears.
• 5. Swap thermostat (if available): If possible, temporarily connect a known-good standard thermostat to the R, C, Y, G, W terminals. If the system runs normally, the original thermostat is likely faulty.

When to call a professional: If wiring is intact and secure but E0 persists, the indoor control board or communicating thermostat may need replacement and configuration by an HVAC technician.