Rheem Furnace Pressure Switch Stuck Open: Causes & Fixes

Last updated Oct 3, 2026 · By fixme.vip Editorial

Rheem furnace pressure switch stuck open: what it means

Before your Rheem furnace lights, the control board starts the inducer motor. The inducer creates a draft through the heat exchanger and vent pipe. A pressure switch senses that draft through a small rubber hose. When the draft is strong enough, the switch closes and tells the board it is safe to start ignition.

“Pressure switch stuck open” means the board started the inducer, but the switch never closed. As a safety measure, the furnace will not start the igniter or open the gas valve.

This is different from the opposite fault, “pressure switch stuck closed.” That code means the switch was already closed before the inducer started, which usually points to a failed switch or a wiring fault.

The flash pattern varies by control board. On many Rheem and Ruud boards it is 2 flashes. Always confirm it against the code chart on the inside of the blower door.

How the fault resets:

• While the thermostat is still calling for heat, the board keeps retrying.
• If the problem persists, many boards enter a lockout that may retry after about an hour.
• Cycling power clears the lockout. Do this only once (see below).

Rheem furnace pressure switch stuck open: common causes, ranked by probability

Technicians typically check venting and draft first, then hoses and condensate, then the inducer, and finally the switch and board.

1. Blocked or restricted vent or combustion-air pipe. Common blockages include snow, ice, leaves, bird or wasp nests, and frost on the PVC vent pipes outside a condensing furnace. A vent pipe that is too long or has too many elbows can also prevent enough draft.
2. Water in the condensate trap, inducer housing, or pressure-switch hose (90%+ models). A clogged trap, or a hose with a sag where water collects, blocks the pressure signal. This is one of the most common causes on condensing Rheem furnaces.
3. Cracked, loose, kinked, or brittle pressure-switch hose, or a plugged port on the inducer housing.
4. Weak or failing inducer motor. Worn bearings, a damaged inducer wheel, or a motor that runs too slowly will not create enough draft to close the switch.
5. Failed pressure switch. The diaphragm may be ruptured or the contacts may be bad. This is less common than the causes above.
6. Wiring or control board fault. A loose connector at the switch, or a board that doesn’t read the closed switch correctly. This is the least common cause.

How to fix Rheem furnace pressure switch stuck open: safe checks first

• Thermostat. Make sure it is set to Heat with the setpoint a few degrees above room temperature. Replace the batteries if the display is dim or blank.
• Air filter. Replace it if it is dirty. It won’t cause this code, but it is quick routine maintenance.
• Outdoor vent and intake pipes. On condensing models, look at the white PVC pipes where they leave the house. Clear away any snow, ice, leaves, or debris you can see and reach from outside. Don’t push anything into the pipes, and don’t take them apart.
• Condensate line. Check that the drain line from the furnace isn’t kinked and isn’t frozen where it exits the house. Check that the condensate pump, if you have one, isn’t full.
• Panels. Make sure the blower door is fully seated so its safety switch is engaged.
• One reset. After clearing a vent or drain blockage, turn the furnace switch or breaker off for 30 seconds, then back on. Do this only once. If the code comes back, stop and call a technician. Repeated resets won’t fix the cause.

How a technician will diagnose it

1. Confirm the fault. The tech reads the flash code and watches a heat cycle to confirm the inducer runs but the switch never closes.
2. Inspect the venting. The tech checks the vent and intake pipes for blockages, sagging sections, and correct length and elbow count.
3. Inspect hoses and drainage. The tech checks the switch hose and housing ports. On condensing models, they also check the condensate trap and drain path, and clean or flush them.
4. Measure the draft. Using a manometer, the tech measures the draft the inducer produces and compares it to the setpoint printed on the switch. A low reading points to a vent, condensate, or inducer problem. A good reading points to the switch.
5. Test the switch and wiring. If the draft is good, the tech checks the switch for continuity and checks the wiring and voltage at the board.
6. Replace the faulty part. The tech replaces only the part that failed, using the exact-match Rheem part. The pressure switch rating is model-specific.

When reviewing a quote, ask for the manometer reading compared with the switch rating. If a tech replaces the switch without measuring draft, it is often a guess.

Symptom, cause and what to do

Rheem furnace pressure switch stuck open repair cost

• Diagnostic visit: $90–$200
• Clearing a vent blockage or nest: $0 DIY, or $100–$250 if done by a technician
• Condensate trap cleaning or hose re-routing: $100–$250
• Pressure-switch hose replacement: $90–$180
• Pressure switch replacement: $150–$350
• Inducer motor replacement: $400–$1,200
• Control board replacement: $400–$1,200
• Venting corrections (rerouting or resizing the pipe): $200–$800 or more

Prices are typical US ranges. Expect to pay more for after-hours visits and older or discontinued models.

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