re: Reasons an AC would intermittently not blow cool?

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I have a similar question hopefully someone on here can help with. My vents blow 104-105 degrees until the outside fan kicks on then cools down to what it is supposed to do. This heat pushes through vent for 5-10 mintues. The AC company changed the thermostat and a defrost board so far and try telling me warm air will come throught until the fan kicks on which sounds like they really have no clue what it is doing. Any help would be appreciated.

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Well you have a heat pump if they changed the defrost board. And heat pump likely has auxiliary heating strips in the air handler that add additional heat during exceeding cold events where the heat pump can’t keep up in heat mode.

105 F air blowing from the ducts in “cool” mode for 5-10 min before the outside compressor starts suggests that something, likely electrical, might be causing the auxiliary heat strips and air handler blower motor to intermittently turn on prior to the outside compressor starting. Heat strips turning on while the HVAC is in cool mode is not an uncommon problem with heat pumps system (I’ve watched a number of Y/T videos with techs identiflying and solving that issue with heat pumps that are not cooling properly) and should be easily diagnosed by an experienced HVAC tech. In the 5-10 minutes that the air handler is blowing hot air before the outside compressor starts look at your thermostat to see if displays “ AUX HEAT, AUX, EMERGENCY HEAT, or HEAT”. If any are those are displayed on the thermostat that certainly will identify it as the source of the problem.

If this is a big company you are dealing with ask them to send out a senior tech that has the most experience with heat pumps. Or look for another HVAC company that has an experienced tech that has lots of heat pump experience.

With a HVAC unit in “cool” mode the outside compressor should turn on simultaneously with indoor blower motor or there might be a very brief delay in the indoor blower motor turning on after the outside unit starts, but not the opposite as you describe.