You just got the keys.

A general home inspection confirms the air conditioner turns on and produces cold air. That is worth having and it is a long way from knowing what you bought.

Inspectors generally do not take refrigerant pressures, measure amp draws under load, read capacitor microfarads against the rating, or open the electrical compartment. Most reports say so explicitly in the limitations section, which almost nobody reads.

What to find out, ideally before closing

How old is it? The data plate on the outdoor unit carries a serial number that encodes a manufacture date. Age is not a diagnosis, but it sets expectations, and Valley equipment works far harder than the national averages assume.

What refrigerant does it use? An older R-22 system with a leak is a very different financial proposition from an R-410A one, because the refrigerant is out of production.

What tonnage, and does it suit the house? The model number usually tells you. An oversized system cools and short cycles and leaves the house clammy. An undersized one never catches up in July.

One system or two? Larger and two storey houses frequently have two, and a seller volunteering that one of them has an issue is not guaranteed.

Is it a package unit or a split system? Roof equipment is a different access situation and a different price for every future repair.

The day you move in

1. Change the filter. Assume the last one is finished and the size is whatever the previous owner could find.
2. Find the air handler. Closet, attic, garage. You need to know where it is before there is water coming out of it.
3. Find the disconnect outside and the AC breaker in the panel.
4. Find the condensate stub outside and confirm it drips when the system runs in summer.
5. Check for a float switch in the drain pan. If there is not one, fit one. It is cheap and its entire job is preventing a ceiling.
6. Look through the condenser fins and clear two feet around the outdoor unit.

Get a baseline

This is the part worth paying for, and it is worth more in year one than any other year.

A check-up measures pressures, amp draws, capacitor values, delta T and airflow, and gives you all of it in writing with photos. On its own that tells you where the system stands. Next summer it tells you what moved, and a reading that moved is worth far more than any single reading on its own.

If the coils have not been cleaned in several seasons, which is normal for a house that just sold, the deep clean tune-up is the one that matters here.

If you have not closed yet

The pre-purchase AC evaluation is a full read on the system before you own it, and it is its own flat price. On a house purchase, finding out the compressor is marginal is worth considerably more before you sign than after.