AERCO BMK 2.0 LN Natural Gas (SN G-11-1861 and above) - Manual (Page 106)

Chapter 8 Benchmark 2.0LN Low NOx Boiler
GF-123
Troubleshooting Installation, Operation and Maintenance Manual OMM-0046_0E
Page 106 of 170 AERCO International Inc.● 100 Oritani Dr. ● Blauvelt, NY 10913. ● Ph: 800-526-0288 PR1 08/20/12
TABLE 8-1. BOILER TROUBLESHOOTING (Continued)
FAULT INDICATION PROBABLE CAUSES CORRECTIVE ACTION
STEPPER MOTOR
FAILURE
1. Air/Fuel Valve out of calibration.
2. Air/Fuel Valve unplugged.
3. Loose wiring connection to the
stepper motor.
4. Defective Air/Fuel Valve stepper
motor.
5. Defective Power Supply Board or
fuse
6. Defective IGST Board
1. Refer to GF-112 and perform Stepper Test (para. 6.3.5) to
ensure stepper motor rotates properly between the 0% (fully
closed) and 100% (fully open) positions. Verify that the VALVE
POSITION bargraph and the dial on the Air/Fuel Valve track
each other to indicate proper operation. If operation is not
correct, perform the Stepper Feedback Calibration (GF-112,
paragraph 6.2.1).
2. Check that the Air/Fuel Valve is connected to the Control Box.
3. Inspect for loose connections between the Air/Fuel motor and
the wiring harness.
4. Replace stepper motor.
5. Check DS1 & DS2 LEDs on Power Supply Board. If they are not
steady ON, replace Power Supply Board
6. Check “Heartbeat” LED DS1 and verify it is blinking ON & OFF
every second. If not, replace IGST Board