Slant/Fin Error Lockout or Hold 88: Outlet T-rise limit — outlet temperature rising too fast
The boiler outlet temperature rose too quickly, indicating insufficient water flow. The manual directs the same diagnosis as Lockout 81 (delta-T limit): check Fuse B, the appliance pump, piping, water pressure (at least 15 PSI), and fouled heat-transfer surfaces. We diagnose and repair it across Greater Vancouver — same-day and after-hours.
The boiler outlet temperature rose too quickly, indicating insufficient water flow. The manual directs the same diagnosis as Lockout 81 (delta-T limit): check Fuse B, the appliance pump, piping, water pressure (at least 15 PSI), and fouled heat-transfer surfaces.
Slant/Fin fault codes can vary by model and series. Use this as a guide — the same code can have more than one cause. Our Technical Safety BC–licensed technicians read the code, confirm it against your unit's manual, and diagnose the true cause before any repair.
Likely causes of Slant/Fin error Lockout or Hold 88
- Insufficient water flow through the boiler
- Failed or air-locked circulator pump
- Low system water pressure (below 15 PSI)
- Closed valve or restricted/incorrect piping
- Scale or magnetite fouling reducing flow/heat transfer
What you can safely check
- Check the pressure gauge reads at least 15 PSI and top up via the fill valve if low
- Confirm the circulator pump runs and the pipe near it gets warm during a heat call
Beyond these checks, do not open the unit or touch gas/electrical parts — BC law requires a licensed gas fitter. Call us for a proper diagnosis.
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Parts often behind Slant/Fin error Lockout or Hold 88
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Slant/Fin Error Lockout or Hold 88 Repair Across Metro Vancouver
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