Carrier Furnace Code 32: Low-Heat Pressure Switch Did Not Close or Reopened (Meaning, Causes, Fixes)

What the code means

Carrier status codes are two digits: the first digit is the number of short flashes and the second the number of long flashes, so code 32 is 3 short flashes followed by 2 long flashes. Before the burners light, the inducer motor pulls air through the heat exchanger and vent, and a pressure switch proves that draft is there. Carrier's troubleshooting guide for its variable-speed furnaces (58MVP, 58MVB and 58UVB, guide 58-06T) defines status code 32 as LOW-HEAT PRESSURE SWITCH DID NOT CLOSE OR REOPENED: the low-heat pressure switch failed to close on a call for low heat, or opened during low heat. The same code also shows if the low gas pressure switch (used on some propane installs) opens. On these furnaces, if the switch doesn't close within 45 seconds the control shuts the unit down, waits 2 minutes and tries again; if it opens after the burners light, the blower runs through its off-delay and the cycle restarts. Carrier's 2-stage guide (58-3T) names the same code LOW-HEAT PRESSURE, DRAFT SAFEGUARD, LOW GAS PRESSURE (IF USED), OR AUXILIARY LIMIT (DOWNFLOW ONLY) SWITCH DID NOT CLOSE OR REOPENED. There the control first speeds the inducer up to high-heat speed to try to close the switch, and if it still hasn't closed after 5 minutes it shuts down and waits 15 minutes before trying again. Code 32 is about the low-heat switch; code 31 is the matching high-heat pressure switch code, and code 43 means the low-heat switch is open while the high-heat switch is closed.

Likely causes

• A plugged condensate drain, trap or drain line, or drain tubing inside the furnace that isn't plumbed correctly, so water backs up and upsets the pressure switch
• Water sitting in the vent pipe, often from a sag in the pipe
• A restricted or incorrectly sized vent or combustion-air pipe, including frost or ice on the combustion-air inlet
• Excessive wind across the vent termination
• Pressure switch tubing that is disconnected, cracked or blocked
• Wiring problems: an open wire, bad terminal or miswired pressure switch circuit
• A failed or out-of-calibration pressure switch
• An inducer motor that is failing, running in the wrong direction, has low supply voltage or a damaged or loose inducer wheel
• On propane installs with a low gas pressure switch, low inlet gas pressure; on some 2-stage downflow models, an open draft safeguard or auxiliary limit switch

Safe DIY checks

1. Confirm the code: look through the sight glass on the blower door and count 3 short flashes followed by 2 long flashes. Write it down before turning power off, because a power reset clears the current flash.
2. Give it time. Depending on the model, the furnace waits 2 or 15 minutes and then retries on its own, so it may come back without help if the cause was brief, like a gust of wind.
3. Check the outdoor intake and vent pipes (on high-efficiency furnaces, the two plastic pipes outside) for snow, ice, leaves, nests or anything else blocking them, and clear it carefully.
4. Check the condensate drain: make sure the drain line isn't kinked or clogged and the trap isn't full of sludge. Carrier's guide lists a plugged condensate drain as one of the first things to look for.
5. With the power off, look at the small rubber tubes connected to the pressure switch. They should be firmly attached, not cracked, and free of water or debris.
6. Look along any vent pipe you can see for a sag or low spot where water could collect; vent pipes are supposed to slope consistently back toward the furnace.
7. Don't jumper or bypass the pressure switch. It's what stops the burners from lighting without proper venting, and bypassing it risks carbon monoxide entering the home.

Parts that commonly fix it

Always match the part number to your exact model.

Related codes

• 12 Carrier Gas Furnace 12
• 13 Carrier Gas Furnace 13
• 14 Carrier Gas Furnace 14
• 22 Carrier Gas Furnace 22
• 24 Carrier Gas Furnace 24

All Carrier codes →

Sources

1. Carrier 58MVP/58MVB/58UVB Troubleshooting Guide 58-06T: Status Code 32 'Low-Heat Pressure Switch Did Not Close or Reopened' (45-second prepurge, 2-minute wait, after-ignition behavior, check list) and the step-by-step code 32 checkout with manometer pressure-drop test
2. Carrier 2-Stage Furnace Troubleshooting Guide 58-3T: Status Code 32 'Low-Heat Pressure, Draft Safeguard, Low Gas Pressure (If Used), or Auxiliary Limit (Downflow Only) Switch Did Not Close or Reopened' (inducer high-speed retry, 5-minute and 15-minute timing, check list)