Weil-McLain GV90+, Manual

Page: 88 / 108

Part number 550-143-010/1021
88
GV90+
series
2
gas-fired water boiler – boiler manual
CHART 6
LIMIT light flashing and POWER light on steady
Electrical shock hazard
— Wherever you see TURN OFF POWER, follow the instructions. Failure to fol -
low instructions could result in severe personal injury, death or substantial property damage.
• Remove SENSOR plug from receptacle on IBC ( Figure 93, page 80 , Item 6).
• Then re-insert.
Does
LIMIT light still flash?
No Yes
• Replace return or supply sensor and harness.
Does
LIMIT
light still flash?
No Yes
• Boiler may now be operating correctly. Verify per normal
sequence of operation ( Figure 75, page 66 ).
• This is NOT a lockout mode. The Integrated Boiler Control
(IBC) should only be signaling that the water temperature
sensor is either shorted or there is an open circuit across the
sensor terminals.
• This situation is usually corrected by replacing the sensor,
as described below.
• Check boiler water temperature.
Use the appropriate resistance range on test meter, mea -
sure the resistance between Thermister 1 (Red) to common
(White) and Thermister 2 (Red) to common. See page 78 ,
Sensor resistance values chart. Both reading should
be within the same range based on the known boiler water
temperature. If either one shows an open circuit or outside
the range on the chart.
• Replace boiler sensor and retest boiler to verify normal
operation.
• Replace IBC.
• Retest.
Troubleshooting
(continued)