Originally Posted by selwaycj
I have been searching for answers to this same problem! Did you ever figure out a fix?
I'm not positive this will help either you or wrenchrob, but here is a Service Manual that covers that model.
Furnace - Suburban Service Manual (NT models)
And, here is a part of it that might help you with the problem ...
Burner Ignites But Shuts Off:
1. Check to be certain that flame sensor is over slots in the main burner and that the main burner flame is burning against the tip of the flame sensor - adjust by bending the sensor probe. NOTE: Sensor probe should be in the inner blue cone of the burner flame, approximately 1/4" to 5/16" above the burner.
2. If the burner still goes off and into lockout, check the wire connections at the flame sensor and the module board.
3. If wire connections are okay, check for continuity through the flame sensor wire.
4. If the continuity of the flame sensor wire is okay, check with microamp meter in series with the flame sensor and flame sensor wire to be certain the flame sensor is generating at least seven microamps within seven seconds after the burner is ignited.
Connect the meter as follows: (+) to sensor wire, (-) to sensor probe. Adjust the position of the sensor probe, check air adjustment and check for carbon deposits on the sensor probe if the reading is less than seven microamps.
5. When the flame sensor circuit is generating at least seven microamps, but the burner still goes off and into lockout, replace the module board.