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Mitsubishi Electric Air Conditioner E6 / E7 / E9 Error Code
Indoor and outdoor units aren't communicating. Here is what it means and how to clear it, easiest fix first.
The indoor and outdoor units have lost their communication link. A tripped outdoor breaker, a damaged or loose interconnecting cable, or a fault on either unit's board can cause it.
E6 and E7 are reported by the indoor unit; E9 is the same type of fault detected by the outdoor unit. Mitsubishi Electric's North American controller manual groups the whole E6 to EF range as indoor/outdoor communication errors. Some outdoor units use E6 for a different fault (a compressor protector opening), so check your manual.
How to fix Mitsubishi Electric E6 / E7 / E9
Check both breakers
Make sure the breakers for the indoor and outdoor units are on. A tripped outdoor breaker is the simplest cause.
Reset the power at the breaker
Switch off the breaker that feeds the air conditioner (some systems have separate breakers for the indoor and outdoor units, so switch off both). Wait about five minutes, switch the power back on and restart the unit to see if the code clears.
When to call a technician
If the code persists, a technician needs to check the interconnecting cable and boards. On a new system, contact the installer.
Parts that commonly cause E6 / E7 / E9
- indoor/outdoor connecting cable
- indoor control PCB
- outdoor control PCB
Order parts by your exact model number so they fit.
Other Mitsubishi Electric air conditioner codes
- Blinking OPERATION lightWall unit's indicator light is flashing
- P1Room air temperature sensor fault
- P2 / P9Indoor coil temperature sensor fault
- P4 / P5Drain sensor or drain pump problem
- PAShut down to prevent a water leak
- P6Freeze or overheat protection
- P8Pipe temperature error
- PbIndoor fan motor error
- FbIndoor control board error
- E0-E5Wall controller communication error
- U1 / UdHigh pressure or overheat protection
- U2Discharge temperature too high or low refrigerant
- U3 / U4Outdoor temperature sensor fault
- U6 / UP / UFCompressor overcurrent
- U8Outdoor fan stopped
- U9 / UHPower supply or current sensor problem
- PLRefrigerant circuit abnormal
Frequently asked questions
What does E6 / E7 / E9 mean on a Mitsubishi Electric air conditioner?
The indoor and outdoor units have lost their communication link. A tripped outdoor breaker, a damaged or loose interconnecting cable, or a fault on either unit's board can cause it.
Can I fix Mitsubishi Electric E6 / E7 / E9 myself?
Only the basic checks. You can safely try the steps above, but E6 / E7 / E9 usually points to a part or fault that needs a technician.
What if E6 / E7 / E9 keeps coming back?
A code that returns after a reset and the checks above usually means a part is wearing out. Note when E6 / E7 / E9 appears (which cycle, how often) and have your model number ready; it helps a technician bring the right part on the first visit.
Last reviewed 2026-10-19. Codes and steps can vary by model; check your owner's manual.