If a mini-split heat pump is blowing cold air while set to heating mode, it is usually performing a standard defrost cycle to melt frost accumulation on the outdoor condenser coil. During this temporary cycle, the system reverses its operation briefly, causing the indoor unit to blow cool air for a few minutes before normal heating resumes. Another common cause is that the system has not yet reached its target temperature and is simply blowing ambient room-temperature air while ramping up the inverter compressor. Additionally, if the unit's refrigerant charge is depleted due to a leak, or if the thermostat sensor is misreading room temperatures, the system will struggle to switch effectively into active heating mode.
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