Message Name:

TEMPERATURE CONTROL ERRATIC WHEN ECS IS IN AUTOMATIC NORMAL MODE OR MANUAL NORMAL MODE

Dust and lint could clog the Ventilated Temperature Sensors (VENTS).

MT37 - located on the left-hand side of the center pedestal in the flight compartment (Fuselage Station 270 LH).

MT28 - located in the middle right-hand side in the cabin (Fuselage Station 495 RH).

• A drift of resistance of a VENT or a Duct Temp Sensor could make the temperature control erratic.
• A slow Hot Air Regulating Shut-off Valve will make a slow increase or decrease of the temperature in one zone.

• Cabin Duct Temperature Sensor (MT26)
• Cockpit Duct Temperature Sensor (MT35)
• Cabin Ventilated Temperature Sensor (MT28)
• Cockpit Ventilated Temperature Sensor (MT37)
• Integrated Air System Controller (IASC) 1 (A55)
• Integrated Air System Controller (IASC) 2 (A56)
• Hot Air Regulating Shut-off Valve (HARSOV) 1 (MPE5)
• Hot Air Regulating Shut-off Valve (HARSOV) 2 (MPE6)
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW300-21-0296 - Low Temperature in Cabin during descent

Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None

Flight Operation Notifications Manual (FONM): None

NOTES:
The Temperature control is as follow:

1. In AUTOMATIC NORMAL MODE, the pilot temperature selection (cockpit and cabin) is compared to the VENTS reading (cockpit and cabin VENTS). The pilot's selection for the cabin and cockpit temperature is within [15°C, 35°C].According to this comparison, the IASC2 controls the 2 zones temperatures by modulating the 2 Hot Air Regulating and Shut-off Valves:

   • HARSOV1 for cockpit
   • HARSOV2 for cabin

   Air Conditioning Unit cooling

   • is measured by the Pack Discharge Temperature Sensor (PDTS).
   • is regulated within [3°C, 50°C] range by the Temp Control Valve (TCV).
   • is controlled by IASC1A (backup by IASC1B).

2. In MANUAL NORMAL MODE, the pilot temperature selection (cockpit and cabin ducts) is compared to the Duct Temperature Sensors reading (cockpit and cabin DTS). The pilot's selection for the cabin and cockpit temperature is within [3°C, 70°C]. The HARSOVs and the Air Conditioning Unit work as the same as the AUTOMATIC NORMAL MODE

If the control of the temperature works well with the ECS system is set in Manual Normal Mode:

For the AUTOMATIC NORMAL MODE do steps 1 to 4 as necessary, do only the steps 3 and 4 for the MANUAL NORMAL MODE.

1. Inspect the VENT Sensor to see if there is any dust or lint. Use a mirror for the Cockpit VENTS. Clean the VENTS as described in the AMM21-61-00-110-801 - Cleaning of the Ventilated Temperature Sensor.
2. Do the VENTS voltage check: With the VENTS powered, do not disconnect it, use long lead and the electrical drawing 21-61-21 (Cabin) or 21-61-25 (Cockpit), check the voltage on within Channel A and then the voltage within Channel B as shown below:

   From	To	Result
   MT28P1-5	MT28P1-6
   MT37P1-3	MT37P1-4

   The voltage equation is: V = 2.731 volts + T/100 (T is Temperature in Celsius)

   1. VA = V ±10 mV (±1°C)
   2. VB = V ±10 mV (±1°C)Make sure VA = VB ±4°C
      NOTE: A 'VENTS Out Of Range' will be detected failed by the IASC and the amber AIR COND TEMP FAIL caution message will be posted to the EICAS.

3. Do the Duct Temperature Sensor (MT26)(MT35) resistance checks: Use Electrical drawing 21-61-29, connect a multimeter between pin 1 and 3 for Channel A, then between pin 4 and 5 for Channel B. Compare the findings with the following chart:

   TEMPERATURE (°C)	RESISTANCE (Ω)	TOLERANCE (°C)	TEMPERATURE (°C)	RESISTANCE (Ω)	TOLERANCE (°C)
   -75	1414110	±1.3	40	1598.1	±0.5
   -65	419370	±1.3	50	1080.9	±0.5
   -55	289124	±1.3	60	746.4	±0.6
   -50	201034.5	±1.3	70	525.6	±0.6
   -45	141586.8	±1.13	80	376.5	±0.6
   -40	100700.4	±1.13	90	274.5	±0.65
   -35	72802.5	±1.13	100	203.4	±0.75
   -25	39125.4	±0.75	110	153.3	±1.00
   -20	29091.9	±0.75	120	117	±1.25
   -15	21886.5	±0.65	130	90.3	±1.25
   -5	12698.1	±0.5	140	70.5	±2.25
   0.0	9795.3	±0.5	150	55.8	±2.5
   5	7617.3	±0.5	160	44.139	±1.5
   15	4713	±0.5	180	28.878
   25	3000	±0.5	200	19.551
   30	2417.1	±0.5	225	12.525

   NOTES:

   1. A Cabin DTS out of range will be detected failed by the IASC and the TRIM AIR FAIL (one or both DTS element out of range) Caution message will be posted to the EICAS.
   2. A Cockpit DTS out of range will be detected failed by the IASC and the AIR COND FAULT (one DTS element out of range) Advisory message will be posted to the EICAS or the TRIM AIR FAIL (both DTS elements out of range) Caution message will be posted to the EICAS.

4. Check that the Hot Air Regulating Shut-Off Valves (HARSOV) modulate with the PACK ON with different settings off the Cabin or Cockpit Knob Temperature. Set to Full Cold and wait for 10 minutes, then set to Full Hot and wait for 10 minutes.
   NOTE: A HARSOV failed open or closed will be detected by the IASC and the TRIM AIR FAIL caution message will be posted to the EICAS Monitor the Cabin and the Cockpit temperatures, interchange the HARSOVs if one zone temperature does not change or the temperature is not reached depending of the cockpit selection then re-do the test. Replace the HARSOV of the zone where the temperature is not reached within 10 minutes.

   • HARSOV1 for cockpit
   • HARSOV2 for cabin

5. Do the close out.