Carrier 69NT40-541-001 Operation And Service page 123

7.22 VENT POSITION SENSOR (VPS)
The vent position sensor (VPS) determines the position of the fresh air vent in near real time via the function code 45.
The fresh air vent position sensor alarm (AL50) will occur if the sensor reading is not stable for 5 minutes or if the
sensor is outside of its valid range (shorted or open). This can occur if the vent is loose or the panel is defective. To
confirm a defective panel, assure that the wing nut is secure and then power cycle the unit.
The alarm should immediately go inactive, check the 4-minute stability requirement. If the alarm reoccurs after the
four minutes and the panel was known to have been stable, then the panel should be replaced.
If the alarm immediately reappears as active, the panel should be replaced.
Upper VPS:
In order to replace the VPS, the panel must be removed and replaced with another upper fresh air panel equipped
with VPS.
Upon installation, a new vent position sensor assembly requires calibration as follows:
1. Rotate the vent to the 0 CMH/ CFM position.
2. Code select 45 will automatically display. Press the Enter key and hold for 5 seconds.
3. After the enter key has been pressed the display will read CAL (for calibration).
4. Press the ALT MODE key and hold for five seconds.
5. After the calibration has been completed, Code 45 will display 0 CMH / CFM.
Lower VPS:
1. Remove Condenser fan guard.
2. If unit is equipped with Partlow recorder, remove 4 Partlow Box assembly mounting bolts and pull Partlow
box assembly away from unit.
If unit is not equipped with Partlow remove left hand access panel to obtain clearance behind Fresh Air
make-up assembly.
3. Remove 2 nuts and 2 washers that hold the slide assembly on. These threads are staked the nuts will be
cutting threads during removal.
4. Remove Slide assembly.
5. The vent position sensor bracket may be riveted in place, drill out rivet heads.
If bracket is bolted; remove bolts, washers and nuts.
6. Note position of wire ties and wire routing for new sensor installation.
7. Remove sensor and bracket assembly from the backside of fresh air make up.
8. Insert new sensor assembly thru clearance hole where the old sensor was removed and route wire harness
as noted in step #7.
9. Mount bracket to unit using bolts, washers and nuts.
10. Wire tie wire harness in locations noted in step 7.
11. Calibrate sensor:
a. Use a multi-meter set to 200k ohms. Connect lead to VPS connector.
b. Turn the gear wheel on the motor all the way to the right (clockwise) until it stops.
c. Adjust the gear wheel counter clockwise until the meter reads: 6.5k ohms (approximately).
d. Install the VPS slide door so that the door is flush against the bottom rail, the motor gear and the door
teeth are meshed, and the gear wheel does not move from the set position.
12. Position slide assembly back on to studs and re-install (2) washers and (2) nuts that secure slide assembly.
13. Stake then ends of the 2 studs on Panel assembly with wire cutters so that nuts will not be easily re moved.
14. Reinstall Partlow box assembly if equipped, or access panel.
15. Reinstall Condenser fan guard.
7–35 T-316