Mini-split & heat pump error codes and fixes, in plain English
Look up your brand’s fault code, understand what each symptom means, and learn exactly what’s safe to fix yourself — and when to call a licensed pro.
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Error codes by brand
Look up any brand fault code and what to do about it.
Explore →Mini-split troubleshooting
Not cooling, leaking, freezing up, won’t turn on — fixes by symptom.
Explore →Maintenance
Filters, coils, drain lines — keep it running and warranty-safe.
Explore →Buying & cost
Costs, sizing, brands, and incentives before you buy.
Explore →Start with a common problem
Mini split not cooling
Read →Mini split not heating
Read →Leaking water inside
Read →Daikin U4 error code
Read →Mitsubishi P8 error code
Read →Mitsubishi E6 error code
Read →Pioneer E1 error code
Read →MRCOOL DF code (defrost)
Read →How to clean the filter
Read →Fujitsu flashing lights
Read →What are mini-split error codes?
Mini-split and heat pump error codes are short letter-and-number messages
(like E6, P4, or U4) that the system
shows on the indoor unit’s display or by blinking its LED lights when it
detects a fault. The code points to the affected area — communication,
sensors, the drain, refrigerant, or the compressor — so you can tell at a
glance whether it’s a simple homeowner fix (a dirty filter, a clogged drain,
a tripped breaker) or a job for a licensed technician. The meaning of each
code varies by brand and model, so always start by identifying your brand,
then confirm the exact code against your unit’s manual. Refrigerant and
high-voltage work requires EPA-608 certification and should never be a DIY task.