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 →Heat pump blowing cold air
Read →Mini split freezing up
Read →What a heat pump costs
Read →Heat pump repair cost
Read →Mini split installation cost
Read →Mitsubishi vs Daikin
Read →How to clean the filter
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.