Ii. Check Stepper Motor And Wiring For Shorts And Opens - Trane CVHE Troubleshooting Manual

Table 6
UCP2 Stepper Module Troubleshooting (Continued)
Condition(s)
Stepper module TP1 -
TP4 OK.
Motor winding
resistance check OK.
Motor does not move.
Stepper module TP1 -
TP4 OK.
Motor winding
resistance check OK.
Motor runs backward.

II. Check Stepper Motor and Wiring for Shorts and Opens

A. During this stage, motor winding and wire resistances will be measured to ensure proper
continuity.
1 If the unit is powered, hit the stop button on the CLD and use manual mode in the service
tools menu to step the actuators all the way to position 0.
2 Unplug power (J2 connector) from the Stepper module.
3 Unplug J6 and J8 from the board.
4 Measure the DC resistance of one of the motor windings by measuring between what would
be Pin (1,3) or Pin (2,4) on the Stepper Board at the unplugged connector (See
5 If the resistance is lower than the limits in
Stepper module and the motor or the in motor winding. Note that nominal values are not
including wire resistances.
6 If the resistance is higher than the limits in
and the motor or a winding is open. Note that nominal values are not including wire
resistances.
CVHE-SB-32A
Possible Problem
Wiring shorted
together at board
edge connector J6 or
J8
Wires shorted
together inside motor
junction box.
Motor does not move
and steps display
does not change on
CLD when using
manual vane control.
Motor runs backward
Possible Cause(s)
*1. metal shavings
from drilling into
UCP2 Panel form
bridge.
2. Loose wire strands
form bridge.
Insulation bared.
UCP2 is not in Stop
Mode and Chiller
module is overriding
manual vane control.
Motor is miswired.
Table 7
there is a short in the wiring between the
Table 7
the wiring between the Stepper module
(Solution(s)
1. Inspect J6 and J8
connectors. Remove
any metal shavings
bridging the wires
before powering mod-
ule.
2. Restrip and rewire
board edge connector.
Seal wire or run new
wire through conduit.
See Table 4 for wiring
diagram.
Hit stop button on CLD,
and try again.
Unplug motor connec-
tor (J6 or J8) from the
Stepper module. Use
Tables 3 and 4 to sway
wire pairs (1, 3) or ((2,
4) so the motor is wired
properly.
Table 7
).
52