Error-Based Diagnostics; Unity Control Board; Unit Hold Down Bracket - Dometic ASCDU15HV 1161 Service Manual

Diagnostic Procedures
Component

5 .2 Error-Based Diagnostics

Refer to the table to diagnose system errors based on the
messages that are displayed on the Q3 control.
Code Description
LO/AC The operating voltage remained
below the acceptable time limit
for three minutes or more (90
Volts for a 100 V system, 100 Volts
for a 115 V system).
HI/PS The head pressure is above the
maximum preset limit.
HP/- - The high pressure circuit is open
on start up.
26
Diagnostic Question

Unity Control Board

Is there a red LED
illuminated on the unity
control board?
Is the system performing
erratically?

Unit Hold Down Bracket

Is the system noisy?
If the AC line voltage drops and
remains below the limit (90 V for a
100 V system, 100 V for a
115 V system) for more than three
minutes, the Q3 control shuts down
the entire system
There is a possible condenser fan
failure.
There is improper airflow through
the condenser.
The condenser coil is dirty.
The high-pressure switch is open.
The high-pressure switch may be
faulty.
Action Based On Status
Use a multimeter to check the voltage between L1 and
L2. Proper voltage should be 115 VAC.
If there is power and no light illuminated, replace the
unity control board.
Check the wiring. If there is a problem with the wiring,
repair as necessary.
Check the Q3 control and display cable. If there is a
problem with the Q3 control, replace the Q3 control.
The unit has multiple locations for hold down brackets:
• Universal: unit hold down brackets that can fit into
any set of two holes found on the three sides of
the unit that have five mounting holes available for
mounting the bracket.
• Fixed: located on the side of the unit with only one
set of mounting holes.
Check the hold down brackets for movement. If the
brackets are loose, tighten them.
Possible Cause Possible Action
For the low-voltage
shutdown function to work
properly, the unity control
board internal voltmeter
should be calibrated.
Test and replace the
condenser fan, if necessary.
Check the condenser for
proper airflow. Remove any
obstructions.
Clean the condenser coil.
Replace the high-pressure
switch.
Test and replace the high-
pressure switch, if necessary.
Air Conditioner
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