L WINDOW HEAT FAIL
(Caution)

The amber 'L WINDOW HEAT FAIL' caution CAS message indicates the respective window heat has failed, and the temperature is too low or too high.

• The respective windshield controller has sensed temperatures out of tolerance.

• Loose Ground Stud Terminal
• Left Window Temperature Controller (A159)
• Left Side Window (MPE59)
• Left Secondary Power Center (A37)Relay (K65)
• Associated Wiring

Advisory Wire/Service Bulletin: 

• AW300-30-0418 - Windshield and Side Window Temperature Sensor Drift

Forum Articles/Infoservice/Newsletter: None

Flight Operation Notifications Manual (FONM): None

NOTES:

• The Windshield Heat Controllers and Side Window Heat Controllers are different part numbers.
• In case of transparency removal, fill the "Transparency Return Form", send a copy to the Bombardier Customer Response Center (CRC) and attach a copy to the returned unit.
• The Window Sensing Element Curve (Temperature - Resistance Curve) is embedded in the Transparency Return Form, but also provided here for the users convenience.
  

1. Perform the Operational Test of the Window Heat System in an effort to duplicate the problem reported IAW AMM TASK 30-41-00-710-802.
2. Locate and inspect ground studs GS2273. Make sure that the electrical connections at ground studs GS2273 is tightened properly.

   

   

3. Check the resistance value of the 3 temp sensors in the respective window. The key to this step is all 3 should be relatively the same. The outside air temp is a factor. The tech can compare resistance readings to that of the known good window on the other side of the aircraft.
   
   

   Condition	S1 - SG (Resistance)	S2 - SG (Resistance)	S3 - SG (Resistance)
   at 65°F	339 ±3 Ω (nominal)	339 ±3 Ω (nominal)	339 ±3 Ω (nominal)
   at 80°F	350 ±4 Ω	350 ±4 Ω	350 ±4 Ω
   OPEN Circuit	> 500 Ω	> 500 Ω	> 500 Ω
   SHORT Circuit	< 212 Ω	< 212 Ω	< 212 Ω

   NOTE: An Overheat condition (> 180°F) could cause a L (R) WINDOW HEAT FAIL caution message (i.e. Long exposure to the sun)
   NOTE: R > 430 Ω (180°F) for any valid sensor (Not open or Not short)
   NOTE: If the resistance reading are not nominal and issue is intermittent check connector P173 (Floor disconnect STN 300LHS)

   1. If a sensor reads outside the nominal values without being OPEN/SHORT, or if a variation of resistance is noticed for the same temperature refer to IS Modsum IS100-30-0002/02/03/05 and AW300-30-0418. An OPEN/SHORT sensor will be rejected by the controller.
   2. If resistance values are within range, continue with next step.
   3. If the fault is intermittent the methods below will help reproducing the fault:

      • While respecting the pressurization safety precaution, pressurize the aircraft by step of 1 psi. Measure the resistance of the sensors at each step to confirm if all the sensors are within the nominal values.
      • Freeze the sensors by applying ice in the sensor area and compare the resistance of the 3 sensors. Repeat the reading while applying heat (the heat of the hand can be sufficient) and confirm if the sensors stay inside nominal values.

4. If troubleshooting is not conclusive, interrogate the MDC as follows:

   •  On the cursor control panel, ensure the toggle switch is to the right and select Anti-Ice, ECS and Fuel buttons simultaneously. The MDC main menu should now be displayed on Display Unit #3.
   • Using the joystick, select Current Faults (if the fault is active) or Aircraft History to research stored faults. From Aircraft History you can then select Fault Message History and locate the fault logged.
   • Select the MDC fault from the drop down below to provide additional information to assist in troubleshooting.
     
     Select an MDC Fault Code/Message:B3-007127 - LEFT SPC RELAY FAILED [L WNDW SPC RELAY]B3-007143 - L WNDW TEMP CTRL FAILED [L WNDW TEMP CTRL]B3-007145 - LEFT SIDE WINDOW FAILED [L SIDE WINDOW]