Carrier furnace: Code 32 — Low-Heat Pressure Switch Did Not Close or Reopened
Try DIY first, then call a pro
What does code 32 mean on a Carrier furnace? On the two-stage variable-speed control, the low-heat pressure switch did not close within 45 seconds of a call for low heat, or it opened during low heat (a low gas pressure switch opening reads the same). The control shuts down, waits 2 minutes and retries. If the switch opens within 5 minutes after ignition, the next cycle runs in high heat only. Official checklist: vent sizing, plugged condensate drain, low inlet gas pressure (if LGPS used), excessive wind, restricted combustion air, pressure switch wiring, failed or out-of-calibration switches, water or sag in the vent piping, disconnected or obstructed pressure tubing.
GOOD NEWS: THE FIRST CHECKS ARE FREE AND TAKE MINUTES.
Try these first — in this order
Drain trap, vent pipe slope, both terminations, and the rubber pressure tubing. A 15-minute visual check.
Switch pressure-drop testing and vent system sizing. DIY part cost: $30–60 — a pro visit for this class of fault typically runs $150–350.
What causes it (in order of likelihood)
- Plugged condensate drain, or water pooling in a sagging vent pipe DIY-CHECKABLE
- Disconnected or obstructed pressure tubing, or a blocked intake or exhaust termination DIY-CHECKABLE
- Failed or out-of-calibration low-heat pressure switch, or miswired switches TECH
- Vent sizing, excessive wind at the termination, low inlet gas pressure TECH
Parts referenced by this code
Always match parts against your model's parts list — part numbers vary within a series.
Applies to
58MVP (Series 170/180) · 58MVB · 58UVB
Different Carrier generations use different code maps. If your series isn't listed, don't assume this meaning — check your blower-door label.
Verified against Carrier 58MVP/58MVB/58UVB Troubleshooting Guide (58-06T), p.7/21-22 — “LOW-HEAT PRESSURE SWITCH DID NOT CLOSE OR REOPENED – Indicates the low-heat pressure switch input failed to close on a call for low-heat, or opened during low-heat. If opens during blower on-delay period, blower will come on for the selected blower off-delay. If opens within 5 minutes after ignition the next heating cycle will be restricted to high-heat.”
Verified against Carrier 58MVP/58MVB/58UVB Troubleshooting Guide (58-06T), p.21 — “If the low heat pressure switch LPS does not make within 45 seconds after a call for heat is initiated the variable speed furnace control starts flashing status code 32, shuts unit down, waits 2 minutes, stops flashing status code 32, and restarts the heating cycle.”
Verified against Carrier 58MVB Service and Maintenance Instructions (58MVB-2SM), p.17 — “Check for: Proper vent sizing. Low inlet gas pressure (if LGPS used). Restricted combustion air supply. Disconnected or obstructed pressure tubing. Defective or miswired pressure switches. Excessive wind. Plugged condensate drain. Water in vent piping, possible sagging pipe”
Last verified 2026-09-05 · how we verify
Related Carrier fault codes
These codes use the same status led — two-stage variable-speed (58mvp / 58mvb / 58uvb) system.
| Pattern | Meaning |
|---|---|
| Code 25 — Model Selection or Setup Error | |
| Code 41 — Blower Motor Fault | |
| Code 15 — Blower Motor Lockout | |
| Code 42 — Inducer Motor Fault |