Heat Won’t Turn Off?! Honeywell Zone Valve FAILS During Test | Slant Fin Boiler Service Call

Heat won’t shut off on the second floor during a New York winter — and it turns into a classic hydronic diagnostic puzzle.In this real, uncut service call from Mikey Pipes – Pipe Doctor Home Services, I respond to a Long Island homeowner with “runaway heat” upstairs. Thermostats off. Boiler at temperature. Zone valve lever loose. Everything seems normal… until we start testing.And that’s when the Honeywell zone valve fails during diagnosis.This video is for:✔️ HVAC Service Technicians✔️ Plumbing & Heating Contractors✔️ Apprentices learning hydronic troubleshooting✔️ Homeowners curious how zone valves and end switches actually workWe walk through:• Identifying a stuck open zone valve• Checking mechanical resistance• Testing thermostats (Honeywell T87 mercury style)• Understanding end switches• Verifying circulator + boiler response• Live wiring replacement (2-screw Honeywell head swap)• Due diligence before leaving the jobThis is how you go the extra mile on a heating service call.The boiler is a Slant/Fin gas boiler, a Long Island legacy manufacturer that many techs still service today. Hydronic heat done right requires patience, logic, and verification.📍 LONG ISLAND, NY HEATING SERVICEIf you’re in Nassau County or Suffolk County, and your:• Heat won’t turn off• Zone valve is stuck open• Boiler keeps running• Baseboard heat won’t shut off• Thermostat not respondingCall the pros.📞 Pipe Doctor Home Services516-348-6300🌐 https://pipedoc.net📍 Long Island, NY🎯 HVAC CONTRACTORS – BECOME AN ACiQ DEALEROn March 10th, 2026 at 2PM, I’ll be LIVE from ACiQ Global HQ in Dayton, Ohio.If you’re a licensed & insured HVAC contractor and want to learn how to offer private-label equipment to your clients:👉 Sign up here:https://aciq.com/mikeypipesFree. No obligation. Massive opportunity.🎉 LIMITED EDITION 2025 MIKEY PIPES POSTER – $42.50Includes:• 5 Stickers• Pen• Card• Magnet💯 100% of proceeds go to charity.PayPal: [email protected]: [email protected]: @PipeDoctorCashApp: $mikeypipesny⏱ CHAPTERS00:00 Heat Won’t Shut Off – Service Call Begins01:25 Boiler Under the Stairs – Initial Diagnosis03:10 Thermostat Testing (Old School Honeywell T87)05:45 Zone Valve Lever Has No Resistance07:20 “Wait… It Just Started Working?”09:15 Boiler at 180° – Why Isn’t It Firing?11:10 Testing the End Switch12:05 Zone Valve FAILS During Testing13:10 Decision Time – Replace Head or Wait?14:00 Wiring the New Honeywell Zone Valve16:20 Verification & Due Diligence17:10 ACiQ Live Event AnnouncementIf you’re a service technician, comment below:👉 Do you replace the head only — or the full body?👉 Ever had a zone valve fix itself before failing again?Subscribe if you’re serious about mastering hydronics.#HVAC #BoilerRepair #ZoneValve