I got an issue with an older Trane Voyager pack that isn't lighting up in heat.
The model is YCD150B4LOBA
The ignitor was bad, so I got a new one, and installed it. On first ignition trial the burner lit for about a second, then went out. It hasn't lit up since,just three trial ignitions, then goes into lockout.
I put my ohm-meter on the ignitor and get 65 ohms. The ignitor gets 125 volts to it during ignition trial. The manifold gas pressure is -2.5" w.c. when the combustion blower is running during pre-purge. The gas pressure goes to -1.3" w.c. when the gas valve is energized.
I took out the ignitor and watched it "glow" during ignition trial, it gets bright orange and doesn't have any "hot spots" or cool spots. I removed the combustion blower and cleaned the little diagonal metal screen. The large diffuser grille is clean. Removed the brass orifice and did not see any obstructions. Put it back together and have same result-- does not light. Any suggestions or input much appreciated.