Slant/Fin Error Lockout or Hold 79: Outlet high limit — boiler outlet over temperature
The boiler outlet temperature exceeded the high-limit setpoint (factory 200°F / 93°C). Documented causes: CH or DHW setpoint plus off-hysteresis exceeding the high-limit setting, a CH/DHW pump problem, or an incorrect 'Outlet high limit' / 'Outlet high limit response' setting. Setting the response to 'recycle and hold' prevents a hard lockout. We diagnose and repair it across Greater Vancouver — same-day and after-hours.
The boiler outlet temperature exceeded the high-limit setpoint (factory 200°F / 93°C). Documented causes: CH or DHW setpoint plus off-hysteresis exceeding the high-limit setting, a CH/DHW pump problem, or an incorrect 'Outlet high limit' / 'Outlet high limit response' setting. Setting the response to 'recycle and hold' prevents a hard lockout.
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 79
- Circulator (CH or DHW) pump not moving water through the boiler
- CH/DHW setpoint plus off-hysteresis exceeding the high-limit setpoint
- Air-bound system or closed isolation/zone valve restricting flow
- Incorrect outlet high-limit setpoint or response setting
What you can safely check
- Confirm the system circulator pump is running and warm to the touch when calling for heat
- Check the pressure gauge reads at least 15 PSI; top up via the fill valve if low
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.
Error Lockout or Hold 79 usually leaves you without heat or hot water and can indicate a safety-related fault. Don't keep resetting it — call for priority after-hours Slant/Fin repair.
Parts Are Professionally Installed — Not Sold for DIY
For your safety and to keep your manufacturer warranty valid, BoilerPart.ca does not sell loose boiler parts over the counter or for self-installation. Under BC regulations, gas appliance components must be installed by a licensed gas fitter. Every part we source is genuine OEM and is professionally fitted, tested, and certified by our Technical Safety BC–licensed technicians as part of a complete repair or installation.
Parts often behind Slant/Fin error Lockout or Hold 79
Genuine Slant/Fin parts we supply and professionally install — never for DIY.
Our Guarantees & Warranties
Every repair and installation is backed by genuine parts, licensed workmanship, and a promise to make it right.
Workmanship Guarantee
Every repair and installation is backed by our written workmanship guarantee. If a part we installed fails because of our work, we make it right.
Genuine OEM Parts
We fit only manufacturer-original (OEM) components so your boiler performs to spec and keeps its factory warranty intact.
Manufacturer Warranty Honoured
As an authorised service provider for the brands we work on, our installs preserve and register your manufacturer parts warranty.
Licensed & Insured
All work is completed by Technical Safety BC–licensed gas fitters (Licence LGA0043870, Boiler Permit LBP0046450). We are fully licensed, bonded and insured for your protection.
Up-Front Pricing
You approve the diagnosis and quote before any work begins. No hidden fees and no surprise charges.
Satisfaction Commitment
Backed by the full HVAC resources of CanroHeat.ca and four decades of service in Greater Vancouver since 1985.
Slant/Fin Error Lockout or Hold 79 Repair Across Metro Vancouver
Related Slant/Fin Safety & Overheat Codes
Frequently Asked Questions
Fix Slant/Fin Error Lockout or Hold 79 Today
Licensed Slant/Fin diagnosis and repair with genuine parts — same-day and after-hours across Greater Vancouver.
A Division of CanroHeat.ca · Licensed Gas Fitters · Serving Greater Vancouver since 1985