EG4 mini split error code 91
IPM over-temperature. Also shown as 91.
- TypeProtection
- SystemCompressor / inverter
- Can I fix it?Homeowner checks, then maybe a tech
What 91 means on a EG4
The inverter power module got too hot and the compressor stopped.
On this platform, 91 is a protection: the system stopped or throttled itself to prevent damage; many clear on their own once conditions return to normal.
Common causes
- A blocked outdoor coil or failed fan.
- Blocked clearance around the outdoor unit.
- Direct sun on the outdoor unit in extreme heat.
How to fix it yourself
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician.
- Look at the outdoor unit: clear leaves, cottonwood fluff, snow or ice from the coil and make sure the fan can spin freely and nothing is stacked against the cabinet.
- Check clearance around the outdoor unit.
- Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.
Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.
When to call a technician
Persistent 91 with a clean coil needs a technician.
Which EG4 units show 91
This page applies to EG4 12K hybrid solar mini split (AC/DC, R32) and 12K / 24K hybrid mini split AC/DC R32 (DWA4 / DWB3 / DGA) units. EG4's own documentation lists 91 as "IPM over-temperature", the same definition used across the EG4 hybrid solar mini split it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.
Where EG4 shows this code
The indoor unit's LED display shows a two-digit number in place of the temperature. EG4 units also run on DC from solar panels, so several codes concern the DC input and the power stage rather than the refrigerant side. 01 to 06 are indoor and communication faults, 31 to 37 are temperature sensors, 51 to 58 are motors, 72 to 79 are voltage and current protections, and 81 to 96 are inverter and compressor drive faults.
Other EG4 codes
Same part of the system as 91:
Questions people ask
Can I reset a EG4 91 code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If 91 comes back, the fault is real and needs the checks above.
Is it safe to keep running a EG4 showing 91?
Not repeatedly. A protection code means the unit stopped itself to prevent damage, and resetting it over and over can turn a cheap repair into a compressor failure. Reset once, check the basics, and stop if it returns.
Do I need a technician for EG4 91?
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician. Persistent 91 with a clean coil needs a technician.
Sources
- EG4 12K Hybrid Solar Powered Mini-Split R32 User Manual (2025), section 14.3 Indoor Unit LED Error Codes
- EG4 12K / 24K Hybrid Mini-Split AC/DC R32 User Manual (10/2025)
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.