Trane 4TVH0086FE000AA Service Manual page 110

Procedure
High pressure sensor connection on main
High pressure sensor has short-circuited
Insufficient refrigerant caused by
The low pressure side is blocked, caused
by crushed or bent pipe, closed EXV or
The evaporator heat exchange is poor
Replace the outdoor main PCB
Notes:
1. High pressure sensor connection is port CN17 on the main PCB (labeled 7 in Figure 5-2.1 in Part 5, 2.1 "Ports").
2. Measure the resistance among the three terminals of the pressure sensor. If the resistance is of the order of mega Ohms or infinite, the pressure sensor has
failed.
3. An insufficiency of refrigerant causes compressor discharge temperature to be higher than normal, discharge and suction pressures to be lower than normal
and compressor current to be lower than normal, and may cause frosting to occur on the suction pipe. These issues disappear once sufficient refrigerant has
been charged into the system. For normal system parameters refer to Table 6-3.4 and 6-3.5 in Part 6, 3.2 "Normal Operating Parameters of Refrigerant
System".
4. A low pressure side blockage causes compressor discharge temperature to be higher than normal, suction pressure to be lower than normal and compressor
current to be lower than normal, and may cause frosting to occur on the suction pipe. For normal system parameters refer to Table 6-3.4 and 6-3.5 in Part 6,
3.2 "Normal Operating Parameters of Refrigerant System".
5. In cooling mode check indoor heat exchangers, fans and air outlets for dirt/blockages. In heating mode check outdoor heat exchangers, fans and air outlets
for dirt/blockages.
H8
PCB is loose 1
No
or failed
2
No
refrigerant leakage 3
No
dirty filter
4
No
No
Yes
Ensure the sensor is connected properly
Yes
Add refrigerant and inspect system for
Yes
Inspect the system and fix the error. If the
Yes
filter is blocked by ice, the piping should
Yes
Inspect the system and fix the error
5
109
Replace the sensor
leaks
be cleaned