Carrier 58MVC Error Code 32: Low-Heat Pressure Switch Did Not Close or Reopened

What Does Code 32 Mean?

Status code 32 on the Carrier 58MVC indicates that the low-heat pressure switch input failed to close when the furnace called for low-heat, or it opened during low-heat operation. If the switch opens during the blower on-delay period, the blower will run for the selected blower off-delay. If it opens within 5 minutes after ignition, the next heating cycle will be restricted to high-heat only.

The low-heat pressure switch monitors the draft created by the inducer motor at low-heat speed. Because the inducer runs slower during low-heat operation, even minor restrictions in the venting system can prevent the pressure switch from closing. This makes code 32 more sensitive to vent issues than codes that appear during high-heat operation.

Common causes include improper vent sizing, a plugged condensate drain, low inlet gas pressure (if a low gas pressure switch is installed), excessive wind, restricted combustion air supply, water in the vent piping, or disconnected/obstructed pressure tubing. Failed or out-of-calibration pressure switches can also cause this code.

Common Causes

How to Fix It: Check Venting, Condensate Drain, and Combustion Air Supply

What You'll Need

• Flashlight
• Wet/dry vacuum (optional, for condensate drain)

Steps

1. Turn off electrical power at the breaker and shut off the gas supply valve Locate the furnace circuit breaker and flip it to OFF. Turn the gas shutoff valve to the OFF position (perpendicular to the pipe). If you smell gas, leave immediately and call your gas company.
2. Inspect the exhaust vent for blockages or sagging Check the entire vent run from the furnace to the exterior termination. Look for sagging sections where water could pool, especially in horizontal runs. PVC vent pipe should slope back toward the furnace for proper condensate drainage. Check the exterior termination for ice, snow, debris, or bird nests.
3. Clear the condensate drain Locate the condensate drain line and trap. A blocked drain can cause water to back up into the heat exchanger and vent system, which disrupts the pressure switch reading. Clear any visible clogs. Pour a small amount of warm water through the trap to verify it drains freely.
4. Verify combustion air supply is adequate If your furnace draws combustion air from the surrounding space, make sure the area around the furnace is not too confined or blocked. Check that combustion air intake pipes (if installed) are clear and not obstructed. The furnace needs adequate air supply to maintain proper draft.
5. Check pressure switch tubing Inspect the small hoses connecting the pressure switch to the inducer housing. Look for disconnections, kinks, cracks, or water trapped in the tubing. Drain any water found in the tubing.
6. Restore power and gas, then test Turn the gas supply valve to ON and flip the circuit breaker to ON. Set your thermostat to call for heat and monitor the furnace through its startup sequence.

When to Call a Professional

Contact a licensed HVAC technician if:

• The code persists after checking the vent, condensate drain, and combustion air supply
• You find sagging vent pipe that needs to be re-supported
• The vent system appears to be improperly sized
• The pressure switch or its tubing appears damaged
• The furnace keeps defaulting to high-heat only mode

✓ Verified against manufacturer service manual — March 2026