E0 Error CodeUpdated 13 days ago

E0 Error Code: Indoor and Outdoor Units Communication Error

General Troubleshooting

Testing Indoor Board Functionality 

1. Power cycle the unit. 
2. Set the unit to fan-only mode. 
3. Check whether the indoor fan starts and responds to fan speed changes from the remote control. 
4. If it does, the problem is likely with the outdoor unit PCB or the communication wiring.  

Ohming Out the Compressor

• Winding-to-winding resistance readings should be nearly equal across all three windings, with no more than 0.3 Ω difference between them, and each reading should be under 3 Ω. If any readings fall outside these limits, the compressor is out of tolerance.
• Ground readings should show OL (open) on all three terminals.

Ohming Out the Outdoor Fan Motor

• Outdoor fan motor readings should be nearly equal across all windings, typically between 45 Ω and 75 Ω.
• A ground test is not required for the outdoor fan motor.

Ohming Out the Reactor

Note: Not all wall-mounted systems have a reactor. Refer to the wiring diagram or parts diagram to verify.

• Disconnect the wires from the reactor and measure the resistance across its two terminals.
• The reactor resistance should be less than 1 Ω, ideally close to zero.

Ohming Out the Electronic Expansion Valve (EEV)

• Check if the unit has an EEV.
• EEVs follow this particular sequence (should be around 50 Ω for each to grey):
  • Black to grey - ~ 47 Ω
  • Orange to grey - ~ 47 Ω
  • Red to grey - ~ 46 Ω
  • Yellow to grey - ~ 46 Ω

Newly Installed Systems

Inspect the System

• Breaker
• External accessories
• Indoor and outdoor model numbers
• Indoor and outdoor terminal blocks
• Valves with hex caps removed (including master valve if inspecting a multi-zone unit). 

Confirm there are No Splices in the Communication Wiring

• If this is a 115V system: Confirm the system is not connected to the incorrect voltage. This will cause the unit's outdoor board to short and require replacing. 

Additional Troubleshooting

• Remove the crimp connectors from the communication wire ends, then connect the bare copper wire directly to the terminals at both the indoor and outdoor units.
• Measure the DC voltage between terminals 1 and 2 on both the indoor and outdoor unit terminal blocks.

Unit Has Been Installed and Operated for More Than Two Weeks

Verify AC Voltage

• Measure the AC voltage between terminals 2 and 3 (L1 and L2, or L and N), starting at the indoor unit(s) and working toward the outdoor unit.
  • Note: AC voltage may be present from each power leg to ground, but if the correct voltage is not present across both power legs (L1 to L2), the unit is not receiving proper voltage. This indicates a voltage drop or a power supply problem.

Obtain System History

• Ask the customer whether there have been any recent power outages, brownouts, power surges, or severe storms. If so, check whether a surge protector is installed for the system.

Inspect the System

• Inspect the system. Look for burn marks on the PCBs, verify that there are no splices in the communication wiring, and check for signs of pests (such as rodents or insects) in or around the PCBs and wiring.