York TM9V080B12MP11 Error Code 8 Red Flashes: Flame Lost Five Times (Recycle)
What Does Code 8 Red Flashes Mean?
This code is set when the furnace successfully ignites but then loses flame five times (four automatic recycles) within a single heating cycle. Each time the flame drops out, the board shuts the gas, purges, and relights; after the fifth loss it stops and enters a one-hour lockout before retrying. The furnace can light — the problem is holding a flame the board can reliably sense.
The most common cause is a dirty flame sensor. That thin rod proves the flame by carrying a small current through it; as oxidation and residue build up, the current fades until the board decides the flame is gone and drops the gas, even though the burners are lit. Low gas pressure can also cause real flame instability, and a faulty gas valve that does not stay fully open is a less common cause.
This is the same flame-sense chain as the continuous amber warning, which flags a weak signal (below 1.5 microamps) before any lockout, and it is distinct from the 7 Red Flashes code, where the furnace never establishes a flame at all. On this model the flame-sensor service includes a metered check of flame current, which is why it is handled by a technician rather than as a homeowner step.
What You'll Notice
- The furnace lights and delivers heat in short bursts, then the flame drops and it relights repeatedly.
- After several relights the furnace goes quiet for about an hour, then tries again.
- The heat feels inconsistent, cutting in and out within a cycle.
- The code may follow a period of the continuous amber weak-flame warning.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Dirty flame sensor | Most common | ✗ Call a pro → |
| Low gas pressure | Common | ✗ Call a pro → |
| Faulty gas valve | Uncommon | ✗ Call a pro → |
How This Is Diagnosed
A technician isolates it in the manual's order: clean the flame sensor and re-measure flame current at the test pad to confirm it now holds above 1.5 microamps, then, if the flame still drops, check gas pressure for a supply problem, and finally inspect the gas valve for one that does not stay fully open. The sensor's ground and wiring are also checked, since a poor ground lowers the sensed current just as a dirty rod does. These involve metered flame-current and gas-pressure checks that are technician tasks on this furnace.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The furnace keeps lighting and dropping out, then locking out for an hour.
- You saw the continuous amber weak-flame warning before this lockout appeared.
- The burner flame looks yellow, lazy, or flickering rather than crisp and blue.
- The code returns soon after a previous flame-sensor cleaning, suggesting a sensor, ground, or gas-pressure issue.
Frequently Asked Questions
Why does my furnace light but keep shutting off with an 8 red flash code?
The burners light, but the flame sensor's signal is dropping out five times during the cycle, so the board keeps shutting the gas as a safety response. A dirty flame sensor is the most common reason.
Is this the same as the furnace not igniting at all?
No. Not igniting at all is the 7 red flash code. The 8 red flash code means the furnace does light but then loses the flame five times during the cycle.
How much does it cost to fix repeated flame loss?
It varies by region and cause. Cleaning a flame sensor is a minor service, while a gas-valve or gas-pressure problem costs more; a technician can confirm the cause after a metered flame-current check.
✓ Verified against manufacturer service manual — March 2026