Need some help with my own unit

My grandson is staying with us this month, so we are using a 3 ton split system unit that is infrequently used. Just got it filled with freon a couple of weeks ago. Every few days, the unit begins to blow warm air (to hot); I haven’t checked Temp on it when it was blowing real hot. This evening it began blowing about 78 from the supply air with the ac on. Supply and suction lines were both HOT to the touch. Last time I shut it off overnight, Matt slept on couch, and fired it back up next morning and it went right back into ac mode. I am doing same tonight to see what happens tomorrow; but it is 95 during the day here. Any ideas?

Is your A/C coil on the air handler freezing up? Ice will slowly build up on a dirty coil.

James, thanks for that question, it reminded me of the other symptom. The coil was warm/hot. It is a split system heat pump capable,but not wired as a heat pump. Thermostat is only a few years old.

Thoughts -

  1. Moisture got in lines when freon was added / now its in line freezing / obstructing the flow after it runs for awhile. Unit gets turned off, moisture unfreezes - cool air flow starts again. Then cycle repeats itself.

  2. The unit is HEAT PUMP cabable - Dave, what does that mean exactly??

Does that mean its got a reversing valve inside the outside condensor; OR does it mean the T-Stat is a HtPump type / JUST not wired up that way; OR does it mean the inside unit has a FuelMaster type add-on JUST not hooked up as Heat Pump; OR ???

Dan, I couldn’t think of another way to describe it. Sorry. The unit has an outside reversing valve, it has just never been wired up as a heat pump. Only use the strips as a furnace.

It is the reversing valve change-over.

You probably have to energize it for A/C and it is failing on the low volt circuit somewhere.

That is the orange wire circuit. (If it is a blue wire circuit it energizes for heat mode and you would be getting a short).

Check the coil on the reversing valve.

If that all checks out, the reversing valve is sticking. It may not have the pressure differential to change over the valve at start up and it is sticking half and half.

If none of this, it is the defrost board .

As you can see, you need someone that knows Heat Pumps. There are several tests on several components that must be checked and tested.

Got a thermal camera?

It should look like this.


This morning, after leaving the unit running all night; I went upstairs and the supply air was 112 deg F. Obviously running in heat mode. There has been no icing of anything.

Dave - Then like David said / call the HVAC Tech.

Now that we know its got a reversing valve, its likely something is sticking and its going to heat mode lieu of moisture freeze-up.

Last year we had a big storm and lightning hit the roof - No biggy, No damage. Next day in A/C mode the heat pump started blow warm then hot air.

Lighning strike had caused a relay or switch to stick AND voila / Heat instead of Cool.

Regardless - This is HVAC Tech stuff / Not homeowner stuff.

Dave -

There’s one other question nobody has asked. WHY did this unit have freon added 2-3 weeks ago? Freon doesn’t just up and run away. Did the unit have a leak OR …???

call the guy back and make him fix the leak like he should have done the first time

Moisture in System / Reversing Valve Issues = Unfortunately Service Tech, NOT us.

Dan, I don’t use that unit often and it was added last month for a annual service as well as my main unit.

Did you fix it yet?

Make sure indoor coil and blower is clean. Dirty coil and blower will reduce air flow. Reduced air flow will drop suction pressure. Inexperienced tech looking at suction pressure only and not taking all pressure and temperature measurements and measuring air flow in correctly believe system low on charge.