What causes Carrier HVAC System 196?

The device wired to R and G tripped. Most often (per HVAC technicians, not Carrier's fault entry) this is a condensate overflow float switch in the drain pan or drain line that tripped because the drain is clogged and water backed up. A condensate pump that stopped working, so water rose in its reservoir or in the pan and tripped the switch (general HVAC background). A faulty float switch, or a broken, loose or shorted wire between the switch and the R and G terminals, so the circuit reads tripped with no water present. The G-terminal setting doesn't match the switch: Carrier's setup asks whether shutdown happens on Normally Open or Normally Closed, and the wrong choice makes the system read a normal switch as tripped. Another add-on device the installer connected to G, such as a different safety switch. The custom label on the thermostat, if one was entered, usually names it.

How do I fix Carrier HVAC System 196?

Read the full message on the thermostat. If your installer entered a G terminal label, it names what's connected, and code 198 instead of 196 means the input is set to alert only. Turn the system off at the thermostat, then look at the indoor unit (furnace with its cooling coil, or fan coil/air handler). Check the drain pan under the coil and any secondary pan for standing water, and look for a float switch clipped to the pan or drain line. If there's water, clear the condensate drain: find the outside end of the line and pull the clog out with a wet/dry vac, or use the cleanout tee near the unit. If you have a condensate pump, make sure it's plugged in and pumps when its reservoir fills. Let the float switch drop back down as the water drains. Once it resets, the R-to-G circuit returns to normal and the system should be able to run again; cycle the thermostat to cooling or heating to check. If the pan and drain are dry and 196 stays, don't jumper the switch or change the G-terminal setting yourself. Bypassing a float switch can let a clogged drain overflow into the house. Call a Carrier dealer, ideally the installer, since they know what was wired to the G terminal and how it was set up.

When should I call a pro for Carrier HVAC System 196?

196 stays on with a dry pan and a clear drain. Water keeps backing up even after the drain is cleared, or the condensate pump has failed. You don't know what's connected to the G terminal and the thermostat shows no label. A technician should identify the device on R and G, test the switch and its wiring with a meter, and confirm the Furnace or Fan Coil G Terminal setting (Function, and Normally Open or Normally Closed for shutdown) matches the switch, as described in Carrier's Infinity control installation instructions. If the drain keeps clogging, a technician can flush the line, check its slope and trap, and replace a failed pump or float switch.

Code: 196❄️ Carrier HVAC System

Carrier Error Code 196: Auxiliary Input (G) Shutdown (Meaning, Causes, Fixes)

Q: What does Carrier HVAC System 196 mean?

Carrier fault 196 on an Infinity or Evolution communicating thermostat (wall control) means "Auxiliary Input (G) Shutdown": a device wired to the G terminal on the furnace or fan coil control board changed state, and the system shut the fan and equipment off on purpose. In a communicating system the G terminal isn't used for a thermostat wire, so an installer can set it up as a shutdown input for an add-on switch. What that switch is depends on your installer, but it's most often a condensate overflow (float) switch, so start by checking the drain pan and drain line at the indoor unit. If the drain is clear and the switch is dry, the switch, its wiring or the G-terminal setting needs a technician. Carrier's Residential Fault Code List (Technical Information TIC2025-0010) lists code 196 as a wall control fault: "Auxiliary Input (G) Shutdown." Its neighbor, 198, is "Auxiliary Input (G) Alert," the warning-only version of the same input. Carrier's Infinity System Control installation instructions explain where it comes from: the installer can set the furnace (or fan coil) G terminal to Disabled, Fan or Shutdown. Set to Shutdown, it watches the R-to-G circuit on the indoor control board, and when that circuit changes to the state the installer picked (Normally Open or Normally Closed) it "shuts off fan and equipment." Carrier notes the shutdown may not be immediate, since blower off delays still run, and that the feature isn't meant as an emergency cutoff. The control also lets the installer type a label for the G terminal alert, which then shows on the main screen and in notification emails. Carrier's documents don't say what device must be connected; HVAC technicians report it is usually a condensate drain float or drain pan switch, but it can be anything the installer wired to R and G.

Reviewed 2026-10-25 · Based on 3 manufacturer & service sources

What the code means

Carrier's Residential Fault Code List (Technical Information TIC2025-0010) lists code 196 as a wall control fault: "Auxiliary Input (G) Shutdown." Its neighbor, 198, is "Auxiliary Input (G) Alert," the warning-only version of the same input. Carrier's Infinity System Control installation instructions explain where it comes from: the installer can set the furnace (or fan coil) G terminal to Disabled, Fan or Shutdown. Set to Shutdown, it watches the R-to-G circuit on the indoor control board, and when that circuit changes to the state the installer picked (Normally Open or Normally Closed) it "shuts off fan and equipment." Carrier notes the shutdown may not be immediate, since blower off delays still run, and that the feature isn't meant as an emergency cutoff. The control also lets the installer type a label for the G terminal alert, which then shows on the main screen and in notification emails. Carrier's documents don't say what device must be connected; HVAC technicians report it is usually a condensate drain float or drain pan switch, but it can be anything the installer wired to R and G.

Likely causes

The device wired to R and G tripped. Most often (per HVAC technicians, not Carrier's fault entry) this is a condensate overflow float switch in the drain pan or drain line that tripped because the drain is clogged and water backed up.
A condensate pump that stopped working, so water rose in its reservoir or in the pan and tripped the switch (general HVAC background).
A faulty float switch, or a broken, loose or shorted wire between the switch and the R and G terminals, so the circuit reads tripped with no water present.
The G-terminal setting doesn't match the switch: Carrier's setup asks whether shutdown happens on Normally Open or Normally Closed, and the wrong choice makes the system read a normal switch as tripped.
Another add-on device the installer connected to G, such as a different safety switch. The custom label on the thermostat, if one was entered, usually names it.

Safe DIY checks

⚠ Before you start

Turn off power at the furnace/HVAC service switch and the breaker before opening panels.

Read the full message on the thermostat. If your installer entered a G terminal label, it names what's connected, and code 198 instead of 196 means the input is set to alert only.
Turn the system off at the thermostat, then look at the indoor unit (furnace with its cooling coil, or fan coil/air handler). Check the drain pan under the coil and any secondary pan for standing water, and look for a float switch clipped to the pan or drain line.
If there's water, clear the condensate drain: find the outside end of the line and pull the clog out with a wet/dry vac, or use the cleanout tee near the unit. If you have a condensate pump, make sure it's plugged in and pumps when its reservoir fills.
Let the float switch drop back down as the water drains. Once it resets, the R-to-G circuit returns to normal and the system should be able to run again; cycle the thermostat to cooling or heating to check.
If the pan and drain are dry and 196 stays, don't jumper the switch or change the G-terminal setting yourself. Bypassing a float switch can let a clogged drain overflow into the house.
Call a Carrier dealer, ideally the installer, since they know what was wired to the G terminal and how it was set up.

🛠 When to call a pro

196 stays on with a dry pan and a clear drain.
Water keeps backing up even after the drain is cleared, or the condensate pump has failed.
You don't know what's connected to the G terminal and the thermostat shows no label.
A technician should identify the device on R and G, test the switch and its wiring with a meter, and confirm the Furnace or Fan Coil G Terminal setting (Function, and Normally Open or Normally Closed for shutdown) matches the switch, as described in Carrier's Infinity control installation instructions.
If the drain keeps clogging, a technician can flush the line, check its slope and trap, and replace a failed pump or float switch.

Parts that commonly fix it

Always match the part number to your exact model.

⚙

Wet/dry vacuum

For pulling a clog out of the condensate drain line from the outside end.

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⚙

Condensate overflow float switch

Only if a technician confirms the switch has failed. It must match the Normally Open or Normally Closed setting chosen for the G terminal.

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⚙

Condensate pump

Only if your system uses one and it no longer pumps water out.

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⚙

Digital multimeter

For checking whether the float switch contacts are open or closed.

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Sources

Last reviewed 2026-10-25. Always confirm against the manual for your exact model number.

Carrier Error Code 196: Auxiliary Input (G) Shutdown (Meaning, Causes, Fixes)

What the code means

Likely causes

Safe DIY checks

🛠 When to call a pro

Parts that commonly fix it

Wet/dry vacuum

Condensate overflow float switch

Condensate pump

Digital multimeter

Related codes

Sources