Rheem R802VA07542117MSA Error Code T045_F: Inducer Lo Pressure Switch Won't Close
What Does Code T045_F Mean?
Code T045_F on the Rheem R802V is set when the low-stage inducer pressure switch fails to close after 60 seconds of continuous inducer operation. When a heat call starts, the inducer (draft) motor spins up to pull combustion air through the burners and push exhaust out the vent. It must build enough negative pressure to close the low-stage pressure switch, which proves the furnace is venting before the Bluetooth Communicating IFC will allow the gas valve to open. If that switch does not close in time, T045_F is set and the furnace waits out a 5-minute lockout before trying again.
This is a two-stage furnace, so it has separate low-stage and high-stage inducer pressure switches, and the inducer must prove draft at each fire rate. On a heat call the low-stage switch is the first gate. The homeowner-safe cause of a failure here is a blocked exhaust or intake termination outside, where ice, snow, leaves, or insect and bird nests choke the draft so the switch cannot close. The same symptom can come from a weak inducer motor, a cracked or disconnected pressure switch hose, or a defective switch, and those are pro-only.
T045_F is tied directly to the inducer lockout codes on this board. Code-T047_F is a low-severity 5-minute inducer soft lockout that auto-retries, and code-A047_F is its alarm-level, persistent counterpart. Note that T045_F is the opposite condition from a switch that is stuck closed: code-A044_F is set when the low-stage pressure switch will not open when it should, whereas T045_F is the switch failing to close when the inducer is running.
What You'll Notice
- The inducer/draft motor runs but the burners never light
- The furnace pauses for about 5 minutes and then tries to start again
- The alphanumeric display flashes T045_F digit by digit
- A visible blockage, ice, snow, or a nest at the outside vent or intake termination
- The problem appears or worsens on very cold or snowy days
Common Causes
How This Is Diagnosed
The outside vent and intake terminations are inspected first, because a blockage there is the most common and the only homeowner-safe cause. If the terminations are clear, a technician checks whether the inducer motor builds adequate draft, inspects the pressure switch hose for cracks or disconnection, and tests the switch itself before replacing any part.
How to Fix It: Clear the Outside Exhaust and Intake Vent Terminations
What You'll Need
Steps
- Turn off electrical power at the breaker or switch AND shut off the gas supply Flip the furnace circuit breaker to OFF, or use the dedicated power switch on or near the furnace, then turn the manual gas shutoff valve to OFF (handle perpendicular to the pipe). If you smell gas, leave immediately and call your gas company. Do not continue until the gas smell is gone.
- Find the vent and intake terminations outside Go outside and locate where the furnace vents through the wall or roof. On this 80% furnace the exhaust termination is where you will look; if a separate combustion-air intake pipe is present, locate that too. They are usually a pair of pipes or a concentric fitting.
- Inspect for ice, snow, leaves, nests, and debris Shine a flashlight into and around each termination. Look for a rime of ice or packed snow, wind-blown leaves, insect or bird nests, or other debris that could choke the draft. In winter, ice at the termination is a common cause of this code.
- Clear visible obstructions from the outside only Wearing gloves, remove any visible debris, nests, snow, or ice you can reach by hand from the outside opening. Do not push tools deep into the pipe and do not open, disconnect, or probe the inducer, pressure switch, or hoses inside the furnace; that work is for a technician.
- Restore power and gas and watch a start cycle Turn the gas valve to ON and restore power. The 5-minute lockout clears on its own; set the thermostat to call for heat. You should hear the inducer spin up, then a click as the pressure switch closes, followed by ignition. If the inducer runs but you never hear the click and no ignition follows, the blockage was not the cause.
When to Call a Professional
Contact a licensed HVAC technician if:
- The outside vent and intake are clear but T045_F keeps returning
- The inducer motor runs weakly, noisily, or does not run at all
- A pressure switch hose is cracked, loose, disconnected, or has water sitting in it
- The fault escalates to the alarm-level code-A047_F or keeps repeating as code-T047_F lockouts
- Any work on the pressure switch, inducer motor, or hoses is needed
Frequently Asked Questions
Why does the furnace wait 5 minutes before trying again?
The 5-minute lockout gives a temporary condition, like a gust of wind or a brief blockage, time to clear and prevents the furnace from rapidly cycling the inducer against a venting problem. After the wait, the control automatically retries.
Is this code more common in winter?
Yes. Ice and packed snow at the outside vent termination are among the most common homeowner-fixable causes, so this code shows up more often during cold, snowy weather. Clearing the termination often resolves it.
Can I replace the pressure switch myself?
No. The pressure switch, its hoses, and the inducer motor require proper diagnosis and correct matched parts, and getting them wrong can defeat a safety that proves the furnace is venting. Limit your action to clearing the outside terminations and route the rest to a technician.
✓ Verified against manufacturer service manual — March 2026