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THE DIFFERENCE
ONE-STOP SHOPPING 
FOR KEY SYSTEM 
PARTS
EXCELLENT
COOLING SYSTEM 
PERFORMANCE
SUPREME CAR PARK 
COVERAGE,  
NEW ENERGY VEHICLES 
PARTS INCLUDED
PROVEN, RELIABLE, 
LONG LIFE-SPAN
EASY INSTALLATION, 
WITH IMPORTANT  
PARTS INCLUDED  
(FIRST FIT)
CORROSION 
PROTECTED 
RADIATORS WITH 
5MM TUBE SPACING
A/C 
OIL 
&
GAS
 FIN
DER
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merica
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m
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29-511
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north
ameri
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issen
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329-5
114
A/C 
OIL 
&
GAS
 FIN
DER
BASIC SYSTEM  
FUNCTIONAL CHECK
SYSTEM CHARGE  
/ STATIC PRESSURES CHECK
SYSTEM LEAKS 
& TIGHTNESS CONTROL
PROPER SYSTEM CHARGE
OPERATING TEMPERATURES 
CHECK
ELECTRIC COMPONENTS CHECK
INNER LOOP CLEANNESS  
& FLUSHING
OPERATING PRESSURES CHECK
TIP: THOROUGHLY TROUBLESHOOTING AND FIXING THE PROBLEM’S  
ROOT CAUSES IS ESSENTIAL BEFORE REPLACING FAULTY COMPONENTS.
TIPS: AN AVERAGE AC SYSTEM LOSES UP TO 30 GRAMS / 1 OZ  
OF REFRIGERANT ANNUALLY.
TIPS: ALWAYS REPLACE SEALS FOR THE DECOUPLED CONNECTION, LUBE 
THEM BEFORE INSTALLATION.
TIPS: KEEP IN MIND THAT NISSENS AC COMPRESSORS ARE  
FACTORY-PRE-FILLED LUBRICANT! AVOID OVERDOSING!
TIP: INFRARED THERMOMETER NISSENS #8900612
TIP: VISUAL INSPECTION NISSENS #8900639 FOR R134A,  
VISUAL INSPECTION NISSENS #8900640 FOR R1234YF
TIPS: POSSIBLE FAILURES BY VARIOUS READINGS DETAILED 
INSTRUCTIONS: FOLLOW THE QR CODE LINK
AC System Service & Diagnostics Procedures
RECOMMENDED BY EXPERTS
Check the temperature of the air that is 
delivered into the cabin.   
 
In short: Idle the engine, AC set on max, 
lowest temperature, 75% blow. A healthy 
system should generate: 
at an ambient temp. of 15-30 °C / 60-90 °F
In short: 6KXWR΍WKHHQJLQHDQGWKH$&V\VWHP&RQQHFWWKHPDQLIROG
gauge set to the service ports, then open the valves. Proper charge 
readings for R134A/R1234yf by the ambient temperature of approx. 20ºC 
/ 68ºF: 
Tightness is necessary for a proper AC system charge and its correct 
operation. Leaks lower system performance and expose other system 
components to premature wear.
Use dry Nitrogen (oxygen-free) or a Nitrogen-based compound with 
Helium/Hydrogen.  Fill the system with the gas and inspect for pressure 
changes spotted during the test time. Recommended, long-lasting test: 
 
COMMON LEAK SPOTS
• Ducts/component surface by abrasion
• Aged rubber hoses’ porosity 
• Component/duct coupling and joints by aged seals 
• Condenser surface and tube joints 
• Compressor housing joints by aged, corroded seals 
• Compressor shaft seal 
• Compressor valves seal
 
 
Pulling a vacuum is a crucial service procedure. If pulled correctly, it 
removes possible moisture from the system and controls its tightness, 
preparing and facilitating the refrigerant’s charge of the system.  
 
Recommended time and pressure
Use only refrigerants and additives approved for automotive climate 
systems. Strictly observe the car manufacturer’s prescription for  
the refrigerant and lubricant type and charge amount. Before charging, 
determine the resting volume of the lubricant and additives in the system
 
Temperatures beyond this range can 
indicate several potential issues. 
In short: Start and idle the engine. Set 
maximum cold air production and maximum 
blow power at the vents. Wait until the 
engine reaches a temperature of 80- 
90°C/180-200°F. 
 
POTENTIAL CAUSES
• Faulty expansion device
• Freezing low pressure hose
• Low refrigerant level
• Leakage in the loop
• Contamination
• Compressor overload (speed)
Run a dedicated onboard diagnostics (OBD)  
for the AC controller, analyze and repair the root  
causes of the registered error codes, and reset  
the codes. Furthermore, inspect: 
 
All AC systems 
• Voltage – is generated acc. to the vehicle specs 
• Fuses – especially AC system-related
• Wiring – conductivity, connections, and insulation
• AC Fan/blower – relay, resistor, control unit 
Manual AC systems
• An electro-magnetic clutch of the AC compressor
• Pressure switches – typically high-pressure side
• Temperature sensors – e.g., on the evaporator
• AC Switch – dashboard/cabin 
Fully/semi-automatic AC systems 
• AC control panel, incl. its relays and controllers
• Pressure transducers
• ECV valve – AC compressor / ECV Tester
• Temperature sensors – cabin, ambient 
• %OHQGGRRUȵDSȇVSRVLWLRQVHQVRUDQGDFWXDWRUVȂ 
LIQHFHVVDU\UHVHWWKHȵDSSRVLWLRQ
• Other sensors – e.g. sun-load sensor etc. 
For the AC system to perform correctly,  
its loop must be clinically clean inside. 
Using a sight glass inspection tool, determine 
whether the AC loop is clean inside.
Visibly too much UV dye in the system
System/compressor exposed to excessive 
overheating
Flush by any of the following:
• compressor seizure
• system blockage
• drier clogging
• Excessive UV dye use
• Excessive oil use
• Presence of sealing agents
In short: Start and idle the engine. Set maximum cold air production and 
around 70% of the blow power at the vents. Wait until the engine reaches  
a temperature of 80- 90°C/180-200°F.
Now, the LP and HP gauge readings need to be considered. 
METHODS
Use only approved 
ȵXVKLQJVROXWLRQV
VSHFLȴFDOO\GHVLJQHG
for cleansing AC 
systems. 
5-15 °C
41-59 °F
BELOW 5 °C
/ 41 °F
Learn 
the complete 
procedures
KEEP IT 
COOL
ΖGHQWLI\DQGȴ[ 
the root causes!
VALUES APPLICABLE FOR 
R134A/R1234yf 
ONLY
APPROPRIATE 
PRESSURE VALUES
IMPROPER  
PRESSURE VALUES
Follow the QR for possible failures by various 
readings and detailed instructions.
For more 
components  
and detailed 
instructions,  
follow the QR
Compare the 
measure with 
the respective 
refrigerant static 
temperature 
vs pressure table
Follow the QR code 
link for methods and 
GHWDLOHGȵXVKLQJ
instructions.
EXAMPLE - Compressor Suction Line
CONTROL THE COLD AIR PRODUCTION 
CONCLUDE THE SYSTEM CHARGE
INSPECT COMPONENTS’ TEMPERATURE
 
INSPECT ELECTRICAL SIGNALS TRANSFER VIA  
THE SYSTEM’S RELAYS, CONTROLLERS AND SENSORS!
FLUSH ALWAYS WHEN REPLACING  
THE AC COMPRESSOR!
INSPECT THE OPERATIONAL PRESSURE 
DIAGNOSE & REPLACE THE SYSTEM KEY COMPONENTS 
PULL A LONG-TIME, DEEP VACUUM
PROPERLY CHARGE THE SYSTEM
PERFORM A LONG-LASTING PRESSURE TEST
FOCUS ON THE VISIBLE
Warning! Avoid overcharging, mixing various lubricant 
types, refrigerant cross-contamination, and overdosing  
of the UV dye. Not observing the above may lead 
to catastrophic system failures, including severe 
damage to the compressor.
Always conduct thorough diagnostics before replacing any 
components, even if they seem faulty. This helps identify the root 
causes of AC system malfunctions and can save your customer 
additional expenses.
EXAMPLE - DARK GREEN COLOR
min 2h to optimally 12h 
min of 16 bar / 232 psi
5-10 °C / 40-50 °F 
4-6 bar / 57 - 87 psi
VISUAL
INSPECTION
60 minutes - by ambient temp > 25°C / 77°F 
90 minutes - by ambient temp < 25°C / 77°F   
29.5 in.-Hg/-14,2 psi/ -0,98 bar or deeper
IMPORTANT! Eliminate the found leakages before the  
new component installation and the refrigerant charge.
TIPS: PRESSURE TESTING KIT (NITROGEN) NISSENS #8900613, 
ELECTRONIC LEAK DETECTOR NISSENS #8900609 / #8900610
TIP: THERMOMETER W/ PROBE NISSENS #8900611
TIPS: THE CONDENSER OR/AND THE AC 
FAN’S POOR CONDITION MAY LEAD TO 
SEVERE COMPRESSOR FAILURES. OIL STAINS 
ATTRACTING DUST INDICATE LEAKS. 
Nissens’ 
Oil & Gas Finder 
 
Our AC refrigerant and oil 
database covers thousands  
of vehicle models, including  
PHEV/EV models. 
2 BAR - VARIABLE COMPRESSOR
1,5 - 3,5 BAR FIXED COMPRESSOR
TIPS: USE AN ECV TESTER TO INSPECT OPERATION OF THE VARIABLE/ECV 
COMPRESSOR, NISSENS #8900602.
COMPONENTS REPLACEMENT
A lower static pressure means the system  
charge is too low, indicating a leak that must 
be found and repaired.
CONDENSER 
 •
surface, if it is: soiled, clogged, deteriorated 
 •
FRUURGHGORRVHȴQVHVSHFLDOO\WKHERWWRPURZ
 •
tubes: bents/deformations
 
SENSORS
 •
inspect connection sockets 
 •
harness/wiring, and insulation 
 •
signs of refrigerant leaks
 
AC FAN 
 •
if it starts/stops, if it runs at all speeds 
 •
if it is adequately balanced, if emits noise
 •
shroud and wings condition
 •
check its attachment to the heat exchangers 
 •
inspect connection sockets, harness/wiring
 
AC COMPRESSOR
 •
if it starts/stops properly
 •
inspect the pulley/free-wheel, and clutch if engages
 •
check belt and the belt’s tensioner
 •
check housing surface if free from cracks, signs of 
leakages or overheating (e.g. burnt label)
 •
by MCV/ECV valves, inspect the valve’s socket 
 •
inspect the electrical connection, harness/wiring
 
HOSES AND DUCTS
 •
surface: abrasion, cracks, bursting and leaks
 •
LIDOXSLSHVDUHIUHHIURPEHQWVȵRZUHVWULFWLRQV
 •
inspect couplings – leaks, broken seals, 
overtightened threads 
 
CABIN AIR INTAKE 
 •
cabin blower – if it starts/stops, if runs on all speeds 
 •
LIWKHUHLVVXɝFLHQWDLUȵRZDWWKHDLUYHQWV
 •
VHQVHRSHUDWLRQRIWKHEOHQGGRRUȵDSV
 •
LQVSHFWWKHFRQGLWLRQRIWKHFDELQDLUȴOWHU
 •
check if the HVAC box is free for debris, clogs, and 
SRVVLEOHDLUȵRZUHVWULFWLRQV
Follow the QR code to read the full details of the procedures  
DQGWRȴQGPRUHWHFKQLFDOLQVLJKWVUHJDUGLQJWKHDXWRPRWLYH 
AC service at nissens.com/H[SHUWV
All Rights Reserved ©Nissens Automotive A/S 2025,  Ormhøjgårdvej 9, 8700 Horsens, Denmark, Disclaimer: nissens.com/disclaimer
Nissens troubleshooting 
and installation tips 
on the key system 
components
AC Compressor 
Installation guide 
([SDQVLRQ9DOYH 
Installation guide 
Condenser 
Diagnostics
Condenser 
Selection
AC Compressor 
Installation tips 
([SDQVLRQ9DOYH 
Diagnostics
COOLING EFFICIENCY BEGINS WITH RELIABLE COMPONENTS
RADIATORS
OIL COOLERS
WATER PUMPS
EXPANSION TANKS
TEMPERATURE SENSORS
FAN CLUTCHES
ENGINE COOLING FANS
FREE A/C System Diagnostic Posters and Oil & Gas Finder Magnets
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