9 blinks
Moderate
Trane · HVAC Systems (AC, Furnaces & Heat Pumps)
Check Polarity / Grounding Issue
Quick Answer
Error code 9 blinks on your Trane HVAC Systems (AC, Furnaces & Heat Pumps) means: Check Polarity / Grounding Issue. This is usually fixable — see the step-by-step guide below.
Likely Causes
How to Fix It
1
Use a multimeter to verify 120VAC between hot and neutral at the furnace disconnect
2
Check for proper voltage between hot and ground (should match hot to neutral)
3
Verify less than 2VAC between neutral and ground at the furnace
4
Inspect the wiring at the furnace junction box for reversed hot and neutral
5
An electrician should check the circuit if the wiring at the furnace is correct but the error persists
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Electrical wire (14/2 or 12/2 Romex)
Wire connectors
Ground clamp
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