Your air conditioner is a mechanical system run by an electrical one, and when it stops on a Hampton Roads afternoon, the cause is usually electrical. That is mostly good news, since the electrical parts are among the least expensive to replace, though they ruin the expensive mechanical parts when left alone, and salt air hurries them along. This post follows the path electricity takes from your panel to the compressor and points out where it tends to fail on the coast. It also explains why having one company handle both the electrical and the cooling side makes these problems simpler to solve.
Following the power from the panel to the compressor
Power arrives at your air conditioner by way of a dedicated breaker in the panel, then a disconnect box mounted near the outdoor unit, and then a contactor inside the unit, a relay that closes when the thermostat asks for cooling. Beyond the contactor, power reaches the compressor and the outdoor fan motor, with a capacitor supplying the push each needs to start. Inside the house, a transformer reduces household voltage for the thermostat and control board, and slender wires carry the thermostat’s signals to both units. Each piece can fail, and many fail in ways you can recognize.
Where it goes wrong
Capacitor fatigue
Inside the outdoor unit sits the capacitor, a small metal cylinder that stores a charge and hands it to the compressor and fan when they need to start. It is the most common electrical failure in an air conditioner, and a long coastal cooling season is hard on it. You will notice it as an outdoor unit humming while the fan sits still, a system that needs several attempts to start, or a click that repeats without the compressor catching. A weak capacitor makes the motors draw extra current on every start, so a small part becomes a large one if it waits.
Contactor wear
Each time the contactor closes, its contacts arc slightly, and across a long cooling season that arcing pits and burns them. Salt air corrodes them faster than inland air, and ants drawn to the contactor’s electrical field are a common cause of failure here when they are crushed between the contacts. A tired contactor may chatter and make the system stutter, or stick closed so the outdoor unit keeps running after the thermostat is satisfied and the bill climbs.
Connections and the disconnect
Every wire in the system ends at a screw or connector that loosens with vibration and corrodes in coastal humidity, and a loose or corroded connection builds resistance, then heat, then melted insulation. The disconnect box on the wall near the outdoor unit is especially exposed, and a corroded one can cause the system to work on some days and not others. Cleaning and tightening them is a standard maintenance item and the quiet reason maintained systems here rarely have electrical fires.
Thermostat wiring
A thermostat with a blank screen usually has dead batteries or a tripped breaker on the air handler behind it. When a system pays no attention to the thermostat at all, the usual causes are a broken low-voltage wire, a loose connection at the terminal strip, or an outdoor wire that a string trimmer or an animal has chewed through. A smart thermostat that flags faults can usually say which of these is happening before the house has a chance to warm up.
The control board and transformer
The control board receives the thermostat’s signal and decides what runs and when, and the transformer supplies its low voltage. Both are vulnerable to the voltage swings of summer thunderstorms and of power returning after an outage, and both can fail after a nearby lightning strike. When a system does nothing at all despite fresh batteries and closed breakers, one of these two parts is often the reason.
The problems in the house itself
Not every electrical problem that stops an air conditioner lives inside it, and this is where having electricians and cooling technicians under one roof helps. When every house on the block is cooling at once, the utility’s voltage can sag far enough to stall compressors and trip breakers, and surges when power returns after a storm damage capacitors and boards across a neighborhood, which whole-home surge protection at the panel absorbs. A breaker that keeps tripping may be worn out, a circuit to the outdoor unit may be undersized for a newer system, or an older panel may be at its limit, and our electrical team handles the panel side on the same visit.
What to watch for
- A system that hums without starting, or that takes several tries to get going.
- A breaker that trips more than once, which is protecting a fault rather than misbehaving.
- Any burning smell near the indoor or outdoor unit, or at the disconnect box.
- Lights that dim when the outdoor unit starts, which points to a circuit or a panel near its limit.
- A unit that keeps running after the thermostat is satisfied, which usually means a contactor stuck closed.
Each is an inexpensive fix when it is caught early and a compressor replacement when it is not. Our maintenance visits test the capacitor under load, inspect the contactor, and clean and tighten the connections every time, which is how these problems get caught before they have the chance to grow. For a failure that has already happened, air conditioning repair begins with the electrical readings, since that is where the answer usually is.
We are here when it quits
Russell’s American Mechanical has served Hampton Roads since 1977. If your air conditioner has stopped, schedule online, use the website chat, or call, and same-day appointments are available by phone when the day allows. The technician will find the failed component, explain it, and give you the price at everyday pricing before replacing it, and members of the Premium Home Care Agreement receive priority response when a covered system fails.