Heat Pump Emergency Decision Tree
Ice on the coil. Won't heat. Won't cool. A real flowchart for diagnosing a heat-pump emergency in the Birmingham metro before the tech arrives.
Get the PDF — No Email Required
11 sections · Print-friendly · Direct download
Who It's For
Anyone in Leeds, Moody, Pinson, Clay, or Springville with a heat pump that just quit doing what it's supposed to.
What's Inside
The 4-symptom decision tree (ice / no heat / no cool / weird sounds), defrost-cycle troubleshooting, reversing-valve symptoms, the 3 questions to answer before the tech arrives.
Why It Matters
Most HVAC problems in Birmingham are preventable or fixable cheaply if you know what to look for. This guide tells you what.
Heat pumps are stranger than regular ACs. They run year-round. They have a reversing valve. They go into defrost cycles. When they fail, the symptoms confuse most homeowners. This decision tree walks you through the four most common heat-pump emergencies in the Birmingham metro — what to look at, what to try, what not to touch.
This is the field-guide version — the same approach we take when we walk into a service call. No marketing fluff. No upsells dressed up as "tips." Just the working tech's playbook, written down.
A Look Inside
Why heat pumps are different
A heat pump is an AC running in reverse during heat mode. Same refrigerant cycle, same compressor, but a reversing valve flips the flow so the outdoor unit pulls heat from outside air and the indoor coil rejects it inside. That means a heat pump that's "broken" can be broken in two completely different modes. Heat failures look nothing like cool failures. This tree handles both.
Symptom 1 — Ice on the outdoor coil
Heat pumps build frost in winter heat mode. That's normal. The system runs a defrost cycle every 30-90 minutes to clear it. A LIGHT coating of frost is fine. A solid block of ice covering the entire coil is not.
- Light frost, system runs normally, goes through defrost cycles — NORMAL
- Solid ice covering the coil entirely, no defrost cycles happening — DEFROST FAILURE
- Ice + system blowing cool air in heat mode — DEFROST SENSOR or REVERSING VALVE issue
- Action: turn the system to OFF, set thermostat to "Emergency Heat" or "Aux Heat" if available. Call a tech.
- …
Symptom 2 — System won't heat
In heat mode, no warm air comes out of registers. Steps:
- 1. Check thermostat — is it set to "Heat" mode? Set point above current temp?
- 2. Listen at outdoor unit — fan running? Compressor humming?
- 3. Walk to a supply register — any air? Cold air? Lukewarm?
- 4. If outdoor unit silent + indoor blower running = reversing valve stuck OR compressor failure. Tech
- …
Download the Full PDF
Written by John, 25-year HVAC technician
John has been turning wrenches on Birmingham HVAC systems for 25 years. Alabama HVAC contractor licensed, bonded, and insured. EPA Section 608 Universal certified. He has walked roofs, attics, crawlspaces, and condenser pads across every neighborhood in this metro and has written every guide on this site from the working tech\'s perspective — not the salesman\'s.
- Back to Emergency AC Repair home
- All services
- Blog — HVAC field notes
- All free guides
- Contact Emergency AC Repair
More guides like this
Emergency AC Failure Checklist (Print + Keep)
A one-page action plan for when your AC dies in the middle of a Birmingham summer night. Print it. Stick it on the fridge. Use it.
After-Hours HVAC Cost Guide: Birmingham 2026
What it actually costs to get HVAC service at night, on weekends, and during holidays in Birmingham — without the surprise-bill drama.
When to Call vs DIY: HVAC Emergency Decision Tree
Some HVAC problems are 5-minute homeowner fixes. Others are "do not touch — call a tech now." Here's how to tell which is which.