Direct answer
The model/serial are on equipment rating plates, not the thermostat. Indoor and outdoor units have separate identifiers.
What this covers
- Residential furnaces, air handlers, heat pumps and central AC
- The exact condition described in the title
- Customer-accessible checks before internal repair or reset
What it does not cover
- ×A different brand, model family or similar-looking code
- ×Internal live-electrical, gas, refrigerant or sealed-system testing
- ×A guarantee that a named component has failed without isolation
Capture the exact state
ReversiblePhotograph each full rating plate.
Separate the likely fault domains
ReversibleRecord which identifier belongs to furnace/air handler, outdoor unit, coil and thermostat.
Correct only the proven, accessible condition
ReversibleUse exact prefix and serial range with the diagnostic legend.
Verify once before going farther
ReversibleConfirm literature matches equipment type, fuel and voltage.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Exact questions
Common follow-ups
What should I record first for “Where to find a furnace, air-handler or heat-pump model number”?+
Photograph each full rating plate.
Does the symptom or code prove a part has failed?+
No. Record which identifier belongs to furnace/air handler, outdoor unit, coil and thermostat.
When should I stop troubleshooting?+
Turn equipment off and do not bypass door switches or touch terminals.
Answer for the exact device and software version shown above.