34 Ignition proving failure

What the control is telling you

Flame was not sensed during trial for ignition; the control retries 3 more times before lockout 14. If flame is lost during blower on-delay, the blower runs its off-delay.

Applies to: 59TP6A two-stage variable-speed ECM multipoise condensing gas furnace, all sizes (040-10 to 120-22)

Likely causes

• Gas valve or manual shutoff off
• Green/yellow ground wire not connected to sheet metal
• Flame sensor grounded, dirty or mislocated
• Igniter or igniter harness failed
• Gas valve not getting 24 V or not opening
• Low inlet gas pressure, wrong firing rate, poor carryover or rough ignition
• Failed control

Test and repair steps

1. Check the gas valve and manual shutoff are on, the green/yellow wire is bonded to the furnace sheet metal, and the flame sensor is not grounded.
2. Run Component Self-Test (R wire off, reset power, SW1-6 ON). The igniter should glow orange/white by the end of the 15-second warm-up.
3. If it does not glow unplug the igniter harness, rerun test (SW1-6 OFF then ON), and check for 115 V between pin 3 and NEUTRAL-L2 for 15 seconds. If 115 V is present, check harness and igniter continuity and replace the bad part; if not, replace the control.
4. Reconnect R and call for heat. Check for 24 V at the gas valve; if none, check connections and then replace the control. If 24 V but no gas flow, check valves are on, then replace the gas valve.
5. If burners do not light check for inadequate carryover, low inlet gas pressure and proper firing rate.
6. If burners light but drop out check flame current during trial for ignition. Nominal is 4.0-6.0 microamps DC; if below 0.5 microamps, clean the sensor with fine steel wool and recheck, and replace the electrode if still low.
7. If current is near normal but burners still drop: repeat in high heat; if still failing replace the control. If high heat works, check low-heat manifold pressure, then carryover and sensor location.

Settings for these units

• Filter sizes by casing width and filter cabinet · 59TP6A
• Minimum clearances to combustibles · 59TP6A