62-61753-21
121 CHECK AMBIENT AIR SENSOR (AAT)
 TRIGGER-ON: Sensor is not within the range of -47° to +70°C (-53 to +158°F)
ï‚· UNIT CONTROL: Engine and standby operation: Alarm Only.
ï‚· RESET CONDITION: Auto Reset when sensor is in range or, alarm may be manually reset
via keypad or by turning the unit off, then back on again.
NOTE: Follow the steps below until a problem is found. Once a repair or correction has been made, the active
alarm should clear itself (refer to reset condition above). Operate the unit through the appropriate modes to see if
any active alarm occurs. Continue with the steps below as necessary.
a. Inspect sensor & connector pins &
terminals. (See wiring schematic
Section 10.)
No physical damage to sensor.
No damage, moisture or corroded pins in plug.
b. Energize sensor circuit.
c. Check for voltage at the sensor
plug between pins A (+) and B
(ground).
Refer to Note 2 Page 7-2.
Voltage should be approximately 12 VDC.
a. Check Sensor resistance. (Refer to
Note 3 page 7-2.)
Refer to Section 8.7.7 for complete table of tempera-
tures and resistance values.
Check Circuits With Another Sensor
a. Substitute known good sensor and
clear alarm. Start unit and run for
30 seconds.
b. Check to see if alarm re-occurs.
Alarm should not come on. (Install new sensor if nec-
essary.)
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