36
SERVICE
Problem Probable Cause Corrective Action
Problems Related to the Gas Valve
If the problem is not in the millivolt circuit of the pilot system, it is most likely in the gas valve
itself.
Follow these steps to check a Honeywell valve:
1.
Complete System Check:
With thermostat
contacts closed and gas cock dial “ON,” main
burner should ignite. If not measure across
terminals 2 and 3 as indicated by the diagram.
If the reading is more than 180MV, replace
the gas valve.
2.
System Resistance Check:
With thermostat
contacts closed and main burner “ON”, measure
the millivolts between terminals 1 and 3 as
indicated by the diagram. Reading should not
be greater than 220MV, If greater, re-check
thermostat leads and connections. Replace
with new or heavier gauge wires if necessary.
If the reading is still greater than 220MV, replace
the thermostat.
3.
Automatic Pilot Dropout Check:
With
thermostat contacts open, depress gas cock
knob with pilot lit until maximum millivolt
output is observed between terminals 1 and
2. Extinguish the pilot and observe the meter.
The sound of the pilot magnet dropping
should be audible. The dropout should occur
between 110 MV and 36MV. If the dropout
occurs outside those limits, replace the gas
valve.
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Summary of Contents for Legend RD18
Page 42: ...40 SERVICE...
