The short answer
When a Carrier Infinity thermostat in Northern Virginia says SYSTEM MALFUNCTION or CALL TECHNICIAN, one of the pieces it talks to reported a fault: the furnace or fan coil, or the heat pump or air conditioner outside. The screen doesn’t always say which, but the control keeps a log of the last 10 events, and the code numbers in it match the flash codes on the equipment’s own board. Find that code first, and don’t factory reset the thermostat, because that wipes the log.
What you’ll see
On the older Infinity Control, the message comes up full screen. Press the right button to dismiss it, and the screen shows SYSTEM MALFUNCTION where the day and time usually are. If the fault is still there, the full message comes back in 24 hours. The Infinity Touch shows its own alert, and both keep running whatever equipment still works.
The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
How to find the code
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| Control | Where the code lives |
|---|---|
| Infinity Touch | Open the menu, then touch and hold SERVICE for 10 seconds or more. Last 10 System Events lists each fault with its date, time and the equipment it came from. Run/Fault History counts faults and run hours. |
| Older Infinity Control | The Service menu holds the Last 10 System Events. A tech reads it on the first visit. |
Write down the code and which equipment it names before anything else. On the Touch, the Last 10 System Events list is cleared by RESET FACTORY DEFAULT under thermostat setup, so leave that alone.
What the codes point at
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| Equipment | Codes | Where to read more |
|---|---|---|
| Gas furnace | The furnace board’s own codes: 31, 33, 34, 41, 45 and the rest | Carrier furnace codes |
| Fan coil | 37 heater output on when it shouldn’t be, 41 blower motor, 44 motor communication | Code 41 |
| Heat pump or AC outside | 16 communication, 45, 46, 47, 48, 69, 73, 74, the 80s lockouts, 96, 97, 99 | Carrier heat pump codes |
A 16, lost communication, is the one most tied to Infinity. The equipment talks over four wires labeled ABCD, and a loose wire, a bad model plug or a brownout that froze the data line all show up as 16. Cycling the power often clears the brownout kind.
Alerts that aren’t a malfunction
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| Alert | When it shows | When it clears |
|---|---|---|
| High Room Temp | 100 degrees for 10 minutes | 98 degrees or under |
| Low Room Temp | 38 degrees for 10 minutes | 40 degrees or more |
| High Humidity | 80 percent for 30 minutes | 78 percent |
| Possible Frozen Coil | The system suspects ice on the indoor coil | Turn cooling off, let it thaw, check the filter; call if it comes back |
| NO SENSOR DATA | The control lost its temperature reading | A sensor or wiring check |
A Low Room Temp alert in January means the heat isn’t keeping up or isn’t running at all. Treat it like a no-heat call.
What you can safely check
- Read and write down the code from the event log.
- Check the filter.
- Check both breakers: the furnace or fan coil switch and the outdoor disconnect.
- Turn the indoor and outdoor power off, wait a minute, and turn them back on. That clears a frozen data line. If the message comes back within a day, call.
What a technician does
We read the event log and the fault counters, then go to the equipment that reported it and read its board. On a communication fault we check each of the four wires end to end. 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.
Our heating check is $67 per system, through December 31: furnace, heat pump or boiler.
Related: thermostat not working, aux heat vs emergency heat, heat pump covered in ice and our Carrier repair page.
Every code meaning here comes from Carrier’s own documents: Infinity Control installation guide, Infinity Touch installation guide and 25VNA 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
What does System Malfunction mean on a Carrier Infinity thermostat?
One of the pieces of equipment the Infinity control talks to reported a fault. The code is in the control’s Last 10 System Events log.
How do I see the error code on a Carrier Infinity Touch?
Open the menu, touch and hold SERVICE for 10 seconds or more, then open Last 10 System Events. It lists each fault with the date, time and equipment.
Will a factory reset clear the System Malfunction message?
It also erases the event log a tech needs. Cycle the power at the furnace and the outdoor unit instead, and call if the message comes back.
Why does my Infinity thermostat say Low Room Temp?
The room was 38 degrees or colder for 10 minutes. The heat isn’t keeping up or isn’t running, so treat it like a no-heat call.
