Lennox SLP98UHV Error Code E 272: Soft Lockout - Pressure Switch Recycle
What Does Code E 272 Mean?
A recycle is what the SureLight Variable Capacity Integrated Control does when a running heat cycle is interrupted and the control restarts the sequence from the beginning. E272 is set when the furnace has gone through too many of these recycles and the most recent one was caused by a pressure switch opening. In other words, the furnace kept getting a heat cycle started, only to have the switch drop out and send it back to the start, until it hit the recycle limit and declared a soft lockout.
This code is closely related to E 271, but the distinction matters. E 271 counts failed ignition retries where the switch opened, while E272 counts recycles — interruptions after the cycle was already underway — where the switch opened. Because the SLP98UHV is a modulating furnace that must keep proving draft as it shifts firing rates, a draft that cannot be held steady will trip the switch mid-cycle and cause exactly this recycle pattern. The manual routes this code to the same troubleshooting as E 223 (the low-fire pressure switch failing to close) and E 225 (the high-fire pressure switch failing to close), because all three come down to whether the vent and inducer can maintain the pressure the switch needs.
The repeated nature of E272 usually means a persistent problem rather than a one-off gust of wind: a partial vent blockage, a sagging vent section that traps condensate, a cracked or water-filled pressure-sensing hose, or a combustion-air inducer that is weakening and no longer moving air reliably. A technician needs to find why the draft keeps collapsing part-way through a cycle.
What You'll Notice
- The furnace starts a heat cycle, shuts down, restarts, and eventually locks out with E 272
- No sustained heat, with the 7-segment display showing E 272
- You hear repeated start-up and shut-down sounds from the inducer before the lockout
- The furnace runs for a short time and then quits, over and over
- The problem worsens in cold or windy conditions when draft is already stressed
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Persistent venting problem causing repeated pressure switch trips | Most common | ✗ Call a pro → |
How This Is Diagnosed
Because E272 is driven by a switch opening after the cycle is underway, a technician focuses on what makes the draft fail mid-run rather than at start-up. A homeowner-safe first step is to inspect the outdoor exhaust and intake terminations for partial blockages such as ice, snow, debris, or nests, which can allow a cycle to begin and then choke the draft as it progresses.
The deeper diagnosis is a technician's job. They walk the entire vent run looking for restrictions, low spots that pool condensate, or joints that leak, check the pressure-switch hose for cracks and trapped water, confirm the inducer motor is spinning strongly and drawing normal current, and measure the operating draft against the low-fire and high-fire pressure-switch settings. Because the fault repeats across recycles, they look for a persistent condition rather than an intermittent one.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace has locked out on E 272 and will not run a full heat cycle
- The code keeps returning after the lockout period clears
- You suspect ice, snow, or debris is partially blocking the vent outside
- You find condensate trapped in the vent or pressure-switch hose
- The inducer motor sounds weak, strained, or intermittent
Frequently Asked Questions
How is E 272 different from E 271?
Both involve a pressure switch opening, but E 271 is a lockout from failed ignition retries, while E 272 is a lockout from too many recycles — interruptions after the heat cycle had already started. E 272 generally means the draft could not be maintained through the cycle, so the furnace kept restarting until it gave up.
Why does the furnace run for a little while before quitting?
With E 272 the pressure switch closes and the cycle begins, but the draft later falls below the switch's trip point and the switch opens, forcing a recycle. After enough recycles the control locks out. That start-then-quit pattern is characteristic of a draft that is marginal rather than completely blocked.
Is this dangerous?
The pressure switch and lockout exist precisely to keep the furnace from running without proven venting, so the safety system is doing its job. That said, repeated venting faults on a gas furnace should be diagnosed by a technician rather than repeatedly reset, since the root cause could involve the vent or a failing inducer.
✓ Verified against manufacturer service manual — March 2026