The short answer
When an American Standard heat pump isn’t heating in Northern Virginia, first rule out the normal stuff: a defrost cycle (the outdoor fan stops and you may see steam for a few minutes) and the aux heat light coming on when it gets cold. Then check the thermostat, the breakers for both the outdoor unit and the indoor air handler, the filter, and whether snow, ice or leaves are blocking the outdoor coil. American Standard’s own guide says to call if the aux heat light stays on all the time when it’s warmer than 30°F, or comes on at all when it’s 50°F outside.
Normal winter behavior that looks like a problem
Defrost
In cold, damp weather the outdoor coil frosts over, and the heat pump melts it off by running backward for a few minutes. The outdoor fan stops, water runs off the coil, and a cloud of vapor can roll off the unit. The installer guide for the variable-speed heat pumps American Standard’s parent company builds (ODR-SVN006C) describes demand defrost: sensors on the outdoor air and the coil start a defrost only when the coil reads cold enough compared with the air. Those sensors only arm when the outdoor air is under 52°F and the coil is under 32°F. The guide even tells installers to place the unit where defrost vapor won’t bother anyone.
The aux heat light
Aux heat is the electric heat strips in the air handler helping out. American Standard’s heat pump owner guide says the light coming on now and then as it gets colder is normal. It also gives the two signs that aren’t: the light stays on continuously when it’s warmer than 30°F outside, or it comes on at all when it’s 50°F. Either one means the heat pump itself isn’t carrying the load. Our aux heat vs emergency heat guide explains the difference.
Warm air, not hot air
Heat pump air feels warm rather than hot, and it runs longer cycles than a gas furnace. If the house holds the temperature, it’s working. If the air at the vents feels cool and the house is losing ground, keep reading. Our blowing cold air in winter guide covers it for any system.
The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
The checks from American Standard’s owner guide
- The thermostat. Set to Heat, a few degrees warmer than the room. Not on Cool, not on Fan only.
- Power, both halves. A heat pump has an outdoor unit and an indoor air handler, and there may be more than one disconnect and more than one breaker. Check them all.
- The filter and the vents. A dirty filter, or closed registers and blocked grilles, cut the heat you get. The guide lists both under not enough heat.
- The outdoor coil. Snow and ice cut the airflow, and the guide says to clear them off as soon as possible. Don’t stack anything on the unit, and keep shrubs back from it. Clear snow by hand or with a broom, never by chipping at the coil.
- The air handler door. If the blower door is off or ajar, the blower has no power. Seat it flat.
When ice is a problem
Frost that comes and goes is defrost doing its job. A coil that stays solid with ice, ice building up from the base, or a unit sitting in a frozen puddle is a problem. The installer guide asks for 12 inches of clearance from walls and shrubs and 5 feet clear overhead, and in cold climates it asks for the unit to be raised 3 to 12 inches so defrost water drains away before it refreezes. A gutter dripping on the top of the unit freezes into a cap. More in our heat pump covered in ice guide.
Thermostat alerts that mean no heat
American Standard’s communicating thermostats (the 824, 850, 1050 and the Link UX360) show an alert number when the heat pump stops. These are the ones behind most no-heat calls, from the 850 user guide and the matching installer guides:
Swipe to see all columns →
Swipe to see all columns →
| Alert | What it means |
|---|---|
| 126.00 | A piece of equipment stopped communicating |
| 79.xx | Low pressure cutout on the outdoor unit; locks out on the third trip |
| 80.xx | High pressure cutout on the outdoor unit |
| 153 | Electric backup heat limit opened (the heat strips overheated) |
| 154 | Low airflow across the electric backup heat |
All of them are in our American Standard error codes guide, and the screen itself in our American Standard thermostat guide.
The usual causes, one at a time
The outdoor unit isn’t running
What you notice: The indoor blower runs, the air is cool or only slightly warm, and outside the fan and the compressor are quiet. The aux light may be on.
What causes it: No power to the outdoor unit (a breaker or the disconnect), a failed capacitor or contactor, or a pressure switch that tripped and locked out. On a communicating system, 79 or 80 alerts point at the pressure switches and 126.00 at a unit that stopped talking.
What you can do: Check the outdoor breaker and the disconnect box beside the unit. Then one power cycle: Set the thermostat to off. Turn off the breaker or the switch for the equipment, wait about five minutes, turn it back on and set the thermostat back. Do it once.
When to call us: If it doesn’t start, or it starts and stops again. Capacitors and contactors get tested with a meter.
It runs, but the house won’t warm up
What you notice: Both halves run, but the air at the vents feels cool and the house loses ground on cold days.
What causes it: Low airflow (filter, vents), a coil caked with ice or dirt, low refrigerant from a leak, or a reversing valve stuck partway.
What you can do: Change the filter, open the vents, clear the outdoor coil.
When to call us: If the air stays cool after that. A refrigerant leak gets found and fixed, not just topped off.
It’s frozen solid
What you notice: The coil is a block of ice, not a dusting of frost, and it stays that way through the day.
What causes it: Defrost isn’t working (a sensor, the board or the reversing valve), water is dripping onto the unit, or the unit sits too low for meltwater to drain.
What you can do: Clear what you can by hand and fix a dripping gutter. Switch to emergency heat if the house is getting cold, and call.
When to call us: Same day. Running a heat pump frozen solid wears out the compressor.
The aux light never goes off
What you notice: Aux heat stays on all day when it’s warmer than 30°F, or shows up at 50°F. The electric bill jumps.
What causes it: The heat pump isn’t keeping up, so the strips carry the house. Anything else on this list can cause it, or the thermostat is set up wrong.
What you can do: Check the outdoor unit is running and the coil is clear.
When to call us: Per American Standard’s guide, this one is a call.
What the visit looks like
The tech checks power at both units, reads any alerts, tests the capacitor and contactor, measures the refrigerant pressures and the temperature split across the coil, and runs a forced defrost to watch it start and end. You get the cause and the price before any part goes in.
The same heat pump sold as Trane: Trane heat pump not heating. A York heat pump: York heat pump not heating. How heat pumps handle a Virginia winter: heat pumps in a Virginia winter. A gas furnace instead: American Standard furnace not turning on. Every brand is in our error codes and warning lights guide, and our American Standard repair page and heat pump repair page have what we fix and what it costs.
The system we put in first
Built to take a beating. Put in by our crew.
Heat lamps, snow and rain on one outdoor unit: that’s Trane’s own film. We’re a Trane Comfort Specialist, on Trane’s own dealer locator, and when you pick a Trane, our crew puts it in.
Films: Trane’s own.
Book an American Standard repair
Call (703) 997-9757 or book online. A diagnostic visit is $99, and the tech reads the code, finds the part that set it and gives you the price before any work starts. We answer day or night. Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. If someone already quoted you a new system, our free second opinion looks at it first. 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 is my American Standard heat pump not heating?
First rule out a defrost cycle. Then check the thermostat, the breakers for both the outdoor unit and the air handler, the filter, and snow or ice on the outdoor coil. If the outdoor unit isn’t running or the air stays cool, call.
Is it normal for my heat pump to stop and steam in winter?
Yes. That’s defrost: the outdoor fan stops, the coil warms to melt the frost, and the water can roll off as vapor. It lasts a few minutes, then heating picks back up.
When is the aux heat light a problem on an American Standard heat pump?
American Standard’s guide says to call if it stays on all the time when it’s warmer than 30°F outside, or comes on at all when it’s 50°F. Now and then in colder weather is normal.
Should I chip ice off my heat pump?
No. Clear loose snow by hand or with a broom and fix any dripping gutter. If the coil stays a solid block of ice, switch to emergency heat and call.
What does alert 126.00 mean on an American Standard thermostat?
A piece of equipment stopped communicating with the thermostat, often the outdoor unit. Check its breaker and disconnect, do one power cycle, and call if it comes back.
