The short answer
When a Carrier air conditioner in Northern Virginia won’t turn on, start with the simple things in order: the thermostat set to COOL and under the room temperature, both breakers (one for the indoor unit, one for the outdoor unit), the outdoor disconnect, the filter and the condensate drain. Then wait 5 minutes, because Carrier’s controls hold the compressor off for 5 minutes to protect it. On two-stage and Infinity models, an amber light on the outdoor board flashes a code that tells you why it stopped.
What you’ll notice
- Nothing happens at all, inside or out.
- The indoor fan runs, but the outdoor unit is silent.
- The outdoor unit hums but the fan doesn’t spin.
- It runs a while, stops, and comes back 15 minutes later.
The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
Check these first
This is our own list, in the order we’d check it on a service call.
- Thermostat: set to COOL, a few degrees under the room temperature, with fresh batteries if it takes them. A blank screen is its own problem: see our Carrier thermostat post.
- Breakers: the indoor unit and the outdoor unit are on separate breakers. Reset a tripped one once. If it trips again, leave it off and call.
- Outdoor disconnect: the gray box on the wall by the unit. Make sure it’s on and the pull-out block is seated.
- Filter: a clogged filter can freeze the indoor coil and shut things down.
- Condensate drain: many systems have a float switch that cuts the AC off when the drain backs up. Water in the drain pan or a full condensate pump is your lead.
- Wait 5 minutes: after a power blip or a thermostat change, Carrier’s time delay holds the compressor off for 5 minutes.
Reading the amber light
Basic single-stage Carrier units have no code light. Two-stage and Infinity outdoor units have an amber status light on the control board, read the same way as a furnace: short flashes are the first digit, long flashes the second. A steady light means standby, 1 flash means low stage and 2 flashes mean high stage. Infinity units also have a green COMM light that stays on while the outdoor unit hears the indoor control, and goes off after 2 minutes without it.
Swipe to see all columns →
Swipe to see all columns →
| Code | What Carrier’s manual says | What it usually means |
|---|---|---|
| 16 | Lost communication with the user interface | Wiring between the thermostat, indoor and outdoor units |
| 31 | High-pressure switch (or discharge temperature switch) open | A dirty outdoor coil, a fan that’s not running, or the refrigerant charge |
| 32 | Low-pressure switch open | Low refrigerant or poor airflow indoors |
| 46 | Brown out: line voltage under 187 volts | A power problem; the unit waits for the voltage to come back |
| 47 | No 230 volts at the unit during a call for cooling | The disconnect is off, or a breaker or wire |
| 71, 72 | The compressor started, then dropped out | The compressor’s internal overload, or a start part |
| 73 | Compressor voltage with no call: contactor stuck closed | A worn contactor |
| 74 | No compressor voltage when it should start | A contactor stuck open or a wiring fault |
On a pressure switch trip, the board shuts the compressor off, runs the outdoor fan for 15 minutes and then tries again. Three trips in a row lock the unit out for 4 hours. That’s why some Carrier AC units seem to stop and start on their own.
What not to do
Don’t keep resetting a breaker that trips, and don’t open the outdoor unit’s service panel: the capacitor inside holds a charge even with the power off. Don’t hose down the outdoor coil with the power on, and don’t run the AC with the indoor coil iced over. Turn it to OFF with the fan ON to thaw it first.
What a technician does
We test the capacitor and contactor, the two parts most likely to stop an outdoor unit, measure the voltage at the unit, read the amber code and its history, check the refrigerant pressures and clean the coil if it needs it. A weak capacitor that leaves the unit humming is a common fix on a hot day.
What it costs to have us look
A repair visit starts with a flat $99 diagnostic, and you get the price of the fix before we touch anything. Our Carrier repair page lists what the common repairs cost. If your outdoor unit is a heat pump, it’s also your heat this winter, and our heating check is $67 per system, through December 31: furnace, heat pump or boiler. Every current deal is on our offers page.
Related: Carrier AC running but not cooling, our AC repair page, Carrier heat pump codes, Carrier Infinity System Malfunction, Carrier furnace codes and our error code and warning light guide.
Every code meaning here comes from Carrier’s own documents: air conditioner and heat pump service manual.
Call or book
Call (703) 997-9757 and tell us the code you counted, or book online from goswiftpro.com/cookiesoffer and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Why won’t my Carrier AC turn on?
Check the thermostat, both breakers, the outdoor disconnect, the filter and the condensate drain. Then wait 5 minutes, because Carrier’s controls hold the compressor off for 5 minutes after a restart.
No. You reset it by turning the thermostat off, then the breaker or disconnect off for a minute and back on. If it trips again, call.
Why does my Carrier AC stop and start again by itself?
On two-stage and Infinity models, a pressure switch trip shuts the compressor off for 15 minutes. Three trips in a row lock it out for 4 hours.
What does the amber light on my Carrier outdoor unit mean?
It flashes a status code. Steady is standby, 1 flash is low stage, 2 is high stage, and two-digit codes like 31 or 47 point at a fault.
How much does an AC service call cost?
A repair visit starts with a flat $99 diagnostic, and you get the price of the repair before any work starts.
