Uploaded March 2026 | Updated September 2026, 2 weeks ago
Is your HVAC system not going into defrost mode? In this video, we break down defrost troubleshooting step by step — covering timers, sensors, and boards so you can diagnose the problem fast.
Learn how defrost timers work (30, 60, and 90-minute runtime cycles), how to test and jump defrost sensors, how to speed up the timer for quick testing, and how to identify failing relays that mimic fan motor issues. We also cover how to trace shorts past the defrost board all the way to the contactor — because the board isn't always the culprit!
Perfect for techs who want clean, efficient diagnostic strategies in the field.
Read all the tech tips, take the quizzes, and find our handy calculators at hvacrschool.com or the HVAC School Mobile App on the Google Play Store (hvacrschool.com/play-store) or App Store (hvacrschool.com/app-store).
Is your HVAC system not going into defrost mode? In this video, we break down defrost troubleshooting step by step — covering timers, sensors, and boards so you can diagnose the problem fast.
Learn how defrost timers work (30, 60, and 90-minute runtime cycles), how to test and jump defrost sensors, how to speed up the timer for quick testing, and how to identify failing relays that mimic fan motor issues. We also cover how to trace shorts past the defrost board all the way to the contactor — because the board isn't always the culprit!
Perfect for techs who want clean, efficient diagnostic strategies in the field.
Read all the tech tips, take the quizzes, and find our handy calculators at hvacrschool.com or the HVAC School Mobile App on the Google Play Store (hvacrschool.com/play-store) or App Store (hvacrschool.com/app-store).
