Trane ACONT900AC43UA Service Manual page 94

Charge Assist™
Yes: Go to Step 6.
No: On an AC unit, replace the Charge Assist™
Control. Heat pump units only check for 24 volts
AC across Charge Assist™ Control LPCO plug J4
(Figure 32A). The fault LED (Figure 32B) should be
flashing in groups of seven flashes if the LPCO
switch is open. If 24 volts AC is present, the heat
pump is locked out by the Low Pressure Cut Out
Switch. Repair system as needed. If there is no
24 volts AC at plug J4, replace the Charge Assist™
Control.
Figure 32A
Step 5
Push in and hold the Mode switch (Figure 33) on the
Charge Assist™ Control for one second. Does the
Status LED now flash slowly?
Figure 33
Yes: Go to Step 4.
No: Replace the Charge Assist™ Control.
CA - A 14
Figure 32B
Step 6
Is there 24 volts AC at plug J3 between its pins Y1 and
B (Figure 34) or Y2 and B (Figure 35)?
Note: There should be 24 volts present only between
pins Y1 and B when LED Y1 is on or 24 volts AC
between pins Y2 and B when LED Y2 is on.
Figure 34
Figure 35
Yes: Charge Assist™ control is working correctly;
fault is with the unit's wiring, its contactors or its
compressor.
No: Replace the Charge Assist™ control.