Haier mini split error code 42
High pressure switch open.
- TypeProtection
- SystemRefrigerant circuit
- Can I fix it?Homeowner checks, then maybe a tech
What 42 means on a Haier
Head pressure exceeded the limit and the high-pressure switch opened. The compressor stops.
On this platform, 42 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 dirty or blocked outdoor coil.
- The outdoor fan not running.
- A service valve not fully open.
- A refrigerant overcharge.
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.
- Confirm every service valve is fully open.
- Pull the front panel and check the filters and the indoor coil. Dirty filters and a matted coil restrict airflow, and airflow problems trigger a surprising number of protection codes.
- 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.
- Anything inside the refrigerant circuit (sensors are fine, but valves, compressors and leaks are not) needs EPA-certified refrigerant handling. That is a technician job.
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
A technician needs gauges to check the charge and the switch.
Which Haier units show 42
This page applies to Haier Haier Flexfit multi-zone (2U/3U/4U…MS2HDA) units. Haier's own documentation lists 42 as "High pressure switch open", the same definition used across the Haier / GE multi-zone outdoor display 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 Haier shows this code
These numeric codes show on the Service Monitor Board display inside the multi-zone OUTDOOR unit (behind the service panel). The indoor units signal a fault with blinking lamps; the number on the outdoor board is what identifies it. Codes 1 to 27 are outdoor-unit faults and protections, 28 to 41 are temperature sensors (28 to 31 and 40 are zone liquid-pipe sensors, 32 to 36 are zone gas-pipe sensors), and 42 to 45 are pressure switches and limits.
Other Haier codes
Same part of the system as 42:
42 on other brands
The same characters do not always mean the same thing. Check the brand on your unit.
- GE Appliances 42 High pressure switch open
Questions people ask
Can I reset a Haier 42 code myself?
Yes. Turn the system off at the breaker for five minutes, then restart it. If 42 comes back, the fault is real and needs the checks above.
Is it safe to keep running a Haier showing 42?
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 Haier 42?
Work through the checks below first; they resolve most cases. If they do not, the repair itself may need a technician. A technician needs gauges to check the charge and the switch.
Sources
- Haier / GE Ductless Multi-Split Heat Pump Service Manual (4.11.22), Error Codes table
Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.