American Standard AUH1B080A9H31A Error Code 9 Flashes: Check Igniter
What Does Code 9 Flashes Mean?
Code 9 (9 Flashes) on the American Standard AUH1B080A9H31A signals a problem with the igniter circuit, potentially combined with a grounding issue. The hot surface igniter must heat to approximately 1800 degrees Fahrenheit to ignite the gas, and any fault in its circuit prevents the furnace from safely starting combustion.
A failed hot surface igniter is the most frequent cause. These ceramic components have a limited lifespan and degrade with each heating cycle. When they fail, the igniter either does not glow at all or produces insufficient heat. A technician can quickly confirm failure by measuring the igniter's resistance — a good igniter typically measures between 40 and 200 ohms depending on type, while a failed one reads as open circuit (infinite resistance).
This code also checks for a grounding issue by monitoring the voltage between the line neutral and the 24VAC common, which should be 2 volts or less. Excessive voltage in this measurement indicates a grounding problem that can interfere with both the igniter circuit and the flame sensing system. A technician with a multimeter can diagnose both issues in a single service call.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Failed hot surface igniter | Most common | ✗ Call a pro → |
| Grounding problem | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace shows 9 flashes and the igniter does not glow during the startup sequence
- The igniter issue may be accompanied by a grounding problem that requires electrical testing
✓ Verified against manufacturer service manual — March 2026