What it is

A cooling PM is a planned visit before or early in the season to clean, measure, and catch small problems before they become a no-cool on the hottest day of the year. A real PM is measurement plus cleaning plus a few component checks — not a quick hose-down and a sticker. Done right, it's the single best way to prevent emergency calls and to extend equipment life.

How it works

Most summer breakdowns trace back to a handful of slow-developing problems: a weakening capacitor, a dirty condenser coil that can't reject heat, a plugged condensate drain, a loose lug heating up, or low airflow. None of those fail all at once — they degrade. A PM is your chance to catch the degradation with a meter and a temperature reading while it's still cheap to fix, instead of meeting it as a midnight emergency.

In the field

Work it as a flow so you're not doubling back:

  1. Talk to the customer first. Any rooms not cooling? Any noises? When did the filter last get changed? Their answer points you at problems a single visit might miss.
  1. Change or check the filter. A loaded filter chokes airflow, drops capacity, and can ice the coil. This is the cheapest performance fix there is.
  1. Inspect and clean the condenser coil. Outdoor coil packed with cottonwood, grass, and dust can't dump heat — head pressure climbs, capacity drops, and the compressor runs hot. Clear debris, straighten obvious fin damage, and wash from the inside out with proper coil cleaner.
  1. Check the capacitor under the meter. Read the run cap's actual microfarads against its rating. A cap drifting low is a compressor or fan motor that's about to struggle to start. This is the highest-value check on the whole visit.
  1. Inspect the contactor. Pitted, burnt, or chattering contacts mean voltage drop and heat. Catch a failing contactor now instead of a stuck or welded one in August.
  1. Tighten and inspect electrical connections. Loose lugs heat up, and heat is the enemy. A quick check with a non-contact temp reader or just snugging the terminals prevents burnt wires.
  1. Read amp draws. Compressor and condenser fan amps against the nameplate. A motor climbing over its rating is a bearing or a cap warning you early.
  1. Clear and treat the condensate drain. Flush the line, confirm it flows, check the trap, and test the float/safety switch. A plugged drain floods ceilings — it's one of the most common and most damaging summer failures.
  1. Verify performance. Let it run, then check pressures, superheat/subcooling, and the supply-to-return temperature split. This tells you if the charge and airflow are right without guessing.
  1. Inspect the indoor side. Blower wheel cleanliness, evaporator coil if accessible, drain pan, and duct/connection integrity at the air handler.
  1. Document and report. Leave the numbers and an honest list of what's good, what's borderline, and what needs attention.

Normal values & targets

Residential cooling ballparks — confirm against the equipment:

  • Run capacitor: within ±6% of printed value (a 45 µF cap reads ~42.3–47.7 µF and is still good); below that, recommend replacement.
  • Cooling temperature split: roughly 16–22°F return-to-supply, tighter in humid conditions.
  • Compressor amps: at or below the nameplate RLA; condenser fan at or below its FLA.
  • Line voltage: ~240V nominal, healthy range about 208–253V depending on supply.
  • Superheat (fixed orifice) / subcooling (TXV): to the manufacturer's target — commonly ~10–20°F superheat or ~8–12°F subcooling.
  • Airflow: ~350–400 CFM/ton.

Common faults & what they mean

  • Weak capacitor on the meter: hard-starting or soon-to-fail motor/compressor — replace before it strands the customer.
  • High head pressure, high subcooling: dirty condenser coil or overcharge — clean first, then re-verify.
  • Low split, iced coil, or low suction: airflow restriction (filter, blower, ducts) or low charge.
  • Burnt/pitted contactor or hot lug: building toward a no-start or a melted connection — address now.
  • Water in the secondary pan or a tripped float: condensate drain plugging — clear it and confirm the safety works.

Tech tips & gotchas

The capacitor check is the highest-payoff thing you do on a cooling PM. A $20 part caught on a tune-up prevents a sweltering no-cool and an emergency rate. Always meter it — don't eyeball it for bulging and call it good, because a cap can read way out of spec without looking bad.

Wash the condenser from the inside out. Spraying the outside drives the dirt deeper into the coil. Pull the top or shoot from inside the fin pack outward so the debris exits the way it came in.

Test the float switch by actually filling or lifting it. "There's a float switch installed" doesn't mean it works. Make it shut the unit off, then confirm the unit restarts when you reset it.

Don't skip the temperature split just because the pressures "look fine." Split is a quick reality check on the whole system from the customer's side of the vent, and it'll flag an airflow problem your gauges might not.

Be honest on the report. A PM's value is trust. Note the borderline cap, the slightly high static, the rusty pan — but don't invent problems. Techs who upsell phantom repairs on a tune-up burn the relationship that makes PMs worth selling.

Safety / code notes

  • Lock out and discharge capacitors before touching terminals — a charged run cap can injure you. Bleed it through a resistor.
  • Confirm the disconnect and overcurrent protection match the nameplate; HVAC circuits are covered by NEC Article 440.
  • Condensate handling and required safety switches/pans fall under the mechanical code (IMC §307; Indiana enforces the IMC).
  • Use coil cleaners per their label and protect yourself and the equipment — some cleaners are caustic.
  • Prove the circuit dead with a verified meter before any electrical service.