Trouble Diagnosis For Unusual Pressure
Diagnose using a manifold gauge whenever system’s high and/or low side pressure(s) is/are unusual. The marker above the gauge scale in the following tables indicates the standard (usual) pressure range. Refer to above table (Ambient air temperature-to-operating pressure table) since the standard (usual) pressure, however, differs from vehicle to vehicle.
Symptom Table
Gauge indication |
Refrigerant cycle |
Probable cause |
Corrective action |
Both high- and low-pressure sides
are too high.
|
The pressure returns to normal is reduced soon after water is splashed on condenser. | Excessive refrigerant charge in refrigeration cycle. | Reduce refrigerant until specified pressure is obtained. |
Air suction by cooling fan is insufficient. | Insufficient condenser cooling
performance.
↓
|
|
|
|
Poor heat exchange in condenser
(After compressor operation
stops, high-pressure decreases
too slowly). ↓ Air in refrigeration cycle. |
Evacuate repeatedly and recharge system. | |
Engine tends to overheat. | Engine cooling systems malfunction | Check and repair each engine cooling system. | |
|
↓ Improper expansion valve adjustment. |
Replace expansion valve. | |
High-pressure side is too high and
low-pressure side is too low.
|
Upper side of condenser and high-pressure side are hot, however, liquid tank is not so hot. | High-pressure tube or parts located between compressor and condenser are clogged or crushed |
|
High-pressure side is too low and
low-pressure side is too high.
|
High- and low-pressure sides become equal soon after compressor operation stops. | Compressor pressure operation
is improper. ↓ Damaged inside compressor packings. |
Replace compressor |
No temperature difference between high- and low-pressure sides. | Compressor pressure operation
is improper. ↓ Damaged inside compressor packings. |
Replace compressor. | |
Both high- and low-pressure sides
are too low.
|
|
Liquid tank inside is slightly clogged. |
|
|
High-pressure pipe located between liquid tank and expansion valve is clogged. |
|
|
Expansion valve and liquid tank are warm or slightly cool when touched. | Low refrigerant charge. ↓ Leaking fittings or components. |
Check refrigerant for leaks. Refer to HA-21, "Leak Test". | |
There is a big temperature difference between expansion valve inlet and outlet while the valve itself is frosted. | compared with the specification. ↓
|
|
|
An area of the low-pressure pipe is colder than areas near the evaporator outlet. | Low-pressure pipe is clogged or crushed. |
|
|
Air flow volume is not enough or is too low. | Evaporator is frozen. |
|
|
Low-pressure side sometimes becomes
negative.
|
|
Refrigerant does not discharge
cyclically. ↓ Moisture is frozen at expansion valve outlet and inlet. ↓ Water is mixed with refrigerant. |
|
Low-pressure side becomes negative.
|
Liquid tank or front/rear side of expansion valve’s pipe is frosted or wet with dew. | High-pressure side is closed
and refrigerant does not flow. ↓ Expansion valve or liquid tank is frosted. |
Leave the system at rest until
no frost is present. Start it again
to check whether or not the malfunction
is caused by water or
foreign particles.
|
Preparation
Special Service Tool
The actual shapes of the tools may differ from those illustrated here.
Tool number
(TechMate No.)
Tool name
Tool number
(TechMate No.)
Tool name
—
(J-39570)
Chassis Ear
Locating the noise
—
(J-50397)
NI ...
Maintenance requirements
Your NISSAN is designed to have minimum maintenance
requirements with long service intervals
to save you both time and money. However, some
day-to-day and regular maintenance is essential
to maintain your NISSAN’s good mechanical
condition, as well as its emissions and engine
performance.
...
P0779 pressure control solenoid B
DTC Description
DTC DETECTION LOGIC
DTC
CONSULT screen terms
(Trouble diagnosis content)
DTC detection condition
P0779
Pressure control solenoid B Inte
When all of the following conditions are satisfied and this state is
maintained
for 0.2 seconds:
T ...