Service manual

6-- 22T--318
Cap and Grommet
Assembly
Probe
Holder
Supply Sensor
Sensor
Wires
Supply
Air
Stream
Evaporator
Back Panel
6mm
(1/4 inch)
Figure 6-29 Supply Sensor Positioning
Evaporator Grille
Combination
Sensor (Mount in
Either Clamp)
Mounting
Clamp
Seal
Figure 6-30 Return Sensor Positioning
6.23 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 55.
The fresh air VPS alarm (AL50) will occur if the sensor
reading is not stable for five 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
four-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 VPS assembly requires
calibration as follows:
1. Rotate the vent to the 0 CMH/ CFM position.
2. Code select 45 will automatically be displayed.
Press the Enter key and hold for five 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 four
Partlow box assembly mounting bolts and pull Part-
low 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 the two nuts and two 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 VPS bracket may be riveted in place. If that’s the
case, 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 through 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 two washers and two nuts that secure slide
assembly.
13.Stake then ends of the two studs on panel assembly
with wire cutters so that nuts will not be easily re-
moved.
14.Reinstall Partlow box assembly if equipped, or ac-
cess panel.
15.Reinstall condenser fan guard.