York TM9T100C16MP11 Error Code Continuous Amber Flash: Low Flame Sense Current

What Does Code Continuous Amber Flash Mean?

The York TM9T100C16MP11 proves its burner is lit using flame rectification: a metal flame-sensor rod sits in the flame and conducts a tiny current back to the control board. A continuous amber flash — a fast flicker with no long pauses — tells you that current has fallen below the 1.5-microamp threshold York uses as its minimum. The furnace is still detecting flame and running, but the margin is thin.

The most common reason is an oxidized or carbon-coated flame-sensor rod. Over many cycles, deposits build on the rod and reduce the current it can conduct, even though the flame itself is healthy. A less common cause is insufficient gas flow: if gas pressure is low, the flame may not fully envelop the rod, weakening the signal.

This is an early-warning condition. If the signal continues to fall and the flame drops out repeatedly, the board escalates to the 8 red flashes code (flame lost five times) and locks the furnace out for an hour. On this model, York specifies confirming the repair by verifying the current is greater than 1.5 microamps at the flame-current test pad, which is why it is treated as a professional check rather than a do-it-yourself fix.

What You'll Notice

• A continuous amber flash (fast flicker, no long pauses) while the burners are lit.
• The furnace runs but may occasionally shut down or short-cycle as the signal wavers.
• Heating becomes intermittent or less reliable than usual.
• If gas flow is low, the burner flame may look weak, lazy, or yellow rather than crisp blue.

Common Causes

How This Is Diagnosed

A technician isolates the cause in a logical order: first the flame-sensor rod is inspected and cleaned of oxidation and carbon, then the gas pressure and flow are checked, and finally the flame current is measured at the board's flame-current test pad to confirm it exceeds 1.5 microamps. If a freshly cleaned sensor still reads low, the investigation moves to the gas supply, gas valve, and burner condition rather than the sensor itself.

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 continuous amber flash persists across multiple heating cycles
• The furnace begins short-cycling or shuts down shortly after the burners ignite
• The burner flame looks yellow or lazy rather than a crisp blue
• The condition escalates to an 8 red flashes flame-loss lockout

✓ Verified against manufacturer service manual — March 2026