Chapter 6: Alarms and System Failure Codes
Alarms
6-8 Service Manual
6.1.16 Humidity Failure Alarm
Note: The Humidity Failure alarm can be caused by non-humidifier issues.
Cause or Circumstances Failure Action
The Motor Drive Failure alarm is
on.
If this alarm activates, it opens
safety relay 2 and disables the
humidifier.
Refer to section 6.1.18 for
troubleshooting.
The Elevating base does not
function. If the elevating base
does not function, then safety
relay 2 is not being energized.
Defective 50 pin ribbon cable
between the relay and control
board.
Check for continuity on pin 34
(safety relay 2 control signal). If
defective, replace the cable. If good,
replace the relay board.
Elevating base functions. Humidifier safety thermostat is
open.
Wait for the heater to cool. Cycle
power to see if alarm resets.
Defective humidifier heater or
humidifier safety thermostat.
Check safety thermostat and
humidifier heater resistance.
Humidifier heater measures
OK.
Relay boards rev 10 or higher. In service Mode, verify mains
voltage is present at the input to
the humidifier isolation
transformer. (J55 1-2)
Relay boards rev 9 or lower.
Humidifier Interface Board is
mounted on relay board.
In service Mode, verify mains
voltage is present at the input to
the humidifier isolation
transformer. (J56 1-2) J56 is on
Humidifier Interface Board
mounted on relay board.
No mains voltage at input to
humidifier isolation
transformer (J55, 1-2).
Defective fuse. Relay boards
rev 10 or higher.
Check fuses F3 and F4 on the relay
board. If OK, continue.
Defective fuse. Relay boards
rev 9 or lower. Humidifier
Interface Board is mounted on
relay board.
Check fuses on humidifier interface
board.
Defective relay board. Replace the relay board.
The Humidity Sensor Failure
alarm indicates that the
humidity sensor failed and the
humidifier is not operating.
Humidity sensor failed. Replace the sensor.
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