REFRIGERANT CHARGING PROCEDURE IN AUTOMOTIVE
We recommend reading this procedure completely
before charging. You may need information before charging you want to
keep handy. Have this procedure with you while charging. Although it can be done
by a single person, we recommend having a helper around.
This procedure outlines the steps to perform
a complete charge. These steps are not to be used to refill or make partial
charges. Toping off requires system parameters monitoring and knowledge, specially
in R134a-based system. Excessive gas will harm your system and will keep it
from cooling properly. MORE REFRIGERANT DOES NOT MEAN COLDER TEMPERATURES
CHARGING IN GAS OR LIQUID - Please
read step 10
Do not use the sightglass (if so equipped) in
R134a-based systems as if were R-12 based.
SPECIAL EQUIPMENT REQUIRED
1) Vacuum pump
2) Gauges (R12 or R134a)
3) Service port adapter (as required in most
R12-based systems) R134a systems do not require adapters other than the couplers
in your gauges in the majority of applications
4) Refrigerant gas (R12 or R134a)
5) Optional: 2-3 ounces of specified oil.
1. Make sure what is the required amount of
gas. From factory, all systems have a decal under the hood that give the data.
If the decal is missing or you are not sure, please specify make, model, and
the type of refrigerant used and whether your system is a factory or an after market
unit here. It is very important to
know if your system has oil. Oil starvation is the main reason of compressor
failure. Oil can be added to the system in two ways: with oil injectors or through
the low side port under vacuum. The procedure to add oil through vacuum is described
here. Some refrigerant charge
and other useful specifications are provided here.
2. Connect both blue and red gauge hoses to
the system's service ports. The discharge port (red hose) is located somewhere
between the compressor and expansion device, either before the condenser or
after it. In R134a systems, the port is the thicker of both, while in R12 systems
is the thinner one. In some aftermarket systems, the port is located in the
back of the compressor. If your ports are located in the compressor, the low
side is marked by an "S" and the high side by an "H". Port
caps have an "L" for low or "H" for high.
3. Open both gauge valves. Connect the common
hose (yellow one) to the vacuum pump. Make sure both gauge needles are zeroed
down. Needle is adjusted by turning a fine screw inside the dial. You must remove
the plastic lens to do this.
4. Turn the pump on. You'll notice that both
gauge readings begin to drop. The blue gauge's needle will even dip into negative
values. The desired low side reading should be less than -25, while the high
side will remain at 0.
5. After approximately 5 minutes, close both
gauge valves. Turn the pump off, and observe the needles. Any movement will
indicate vacuum loss. The faster the movement, the greater the loss. If after
two minutes you don't see any needle movement, open both valves, turn the pump
on, and continue vacuum for not less than 30 minutes. Close both valves then
turn the pump off.
6. Get ready to charge. Have the necessary refrigerant
amount handy. Cans make charging easier and more precise unless you have a charging
cylinder or a precision scale.
7. Disconnect the yellow hose from the vacuum
pump and connect it to the can tap or charging cylinder valve. You can charge
in two ways: liquid (can upside down) or gas. Liquid charging is a lot faster
but not recommended unless you extreme care or have experience. Traditional
(gas) charging is slower but safer.
8. Once you've decided, and with the can or
container connected, unscrew the top yellow hose connection (at the gauges)
allowing refrigerant to escape for a couple of seconds. This will purge the
air out of the hoses so you make sure that all you dispense is refrigerant.
You can do this venting in liquid form so you can see when a fine, steady stream
of refrigerant escapes indicating that all the air is gone from the hose. Don't
breathe refrigerant and don't charge in a flammable environment.
9. "Flood" the system with liquid
refrigerant (can upside down) by opening the red valve (high side) until it
won't take anymore. Close the red valve. Jump the low pressure cycling switch
(if so equipped). If you don't know what this is or where it is, ask for help
10. Turn the engine on. Turn the A/C into MAX
on its third or higher blower speed. You'll note that both gauge readings are
now positive. The red gauge should read between 100 and 150, while the blue
gauge between 5 and 15. If you are charging with cans, don't forget to purge
air out the hose after hooking a new can as described in step 8 above. Now,
charge will continue through the low (blue) side (see note below)
. If you haven't jumpered any switch (you don't have to), you'll
notice the compressor cycling frequently on and off. That is normal. The cycling
will disappear as you dispense more refrigerant. The only disadvantage of frequent
compressor cycling is that charge will take longer. Needles will move up and
down with every cycle. This is normal. Do not jump any switch unless you are
NEVER OPEN THE RED VALVE WHILE CHARGING.
The red valve is to be opened only during pre-charge, vacuum, or when a system
is evacuated. Its function is keeping an eye on the high side only. It must
be closed at all times. If you have any doubts, wait until you receive information.
Severe injury or death may occur. Remember: ALWAYS wear safety goggles. NEVER
charge your system in a closed environment.
OR LIQUID CHARGING?
There are two ways to charge:
gas (can or cylinder up), or liquid (can or cylinder upside down). A compressor
is designed to compress gas. Direct liquid charge will harm the compressor if
suction pressure is not controlled. Liquid charging is faster, yet is riskier.
Liquid charging should be made by professionals or under supervision. Liquid
charging can be done if the suction port is away from the compressor (some compressors
have the suction valve in its body).
Liquid charging can be done never
exceeding a 50 PSI suction pressure. If you can't control it, charge in gas
form. In cooler weather, cans may freeze. You may immerse them in water and
shake them while charging.
about 2/3 of the charge has been dispensed into the system, spray water in the
condenser to optimize heat exchange and speed the process. When you get the
condenser wet, vent temperature is likely to raise. This is normal. You'll also
note pressure drop in both gauges.
12. Once the specified amount has been dispensed,
close the blue valve. Let the system run for a minute. Turn the A/C off and
then the engine. Wait another minute and disconnect the couplers from the service
ports. Disconnect the low side first. If you jumpered a switch, reconnect it
Optimum cooling performance is attained after
10 minutes of operation. Our own acceptance criteria is at least 50°F in
the center vent to the driver side at idle after 10 minutes or less. Remember:
cooling increases while the vehicle is in motion.
Due to the physical properties
and chemical composition, R134a and R12 charging amounts are different. Never,
if you are retrofitting, charge the same or specified amount of R12 with R134a.
If in doubt, please e-mail us here. Do not use this
procedure if you are using any other refrigerant. This is just for R12 or R134a.
Although procedures and parameters may be similar, we do not use nor
recommend alternative refrigerants.
HOW TO DETERMINE OPERATING PRESSURES
Every vehicle has its own operation
parameters specification. Depending on whether or not the vehicle has a factory
or an after market system, and whether it was retrofitted or is still original,
among others. There is no established calculation to determine the exact operating
The low pressure (blue gauge) should
be 35 or less at idle, regardless of the type of gas. Only if you're running
a dual system, the low pressure may be between 45 and 50 at idle.
The high pressure, for starters, is
directly related to ambient temperature: the higher the temperature, the higher
the higher the pressure.
Bear in mind that dispensing a complete charge
without lowering the pressures with water will result in higher readings. This
is normal, and that is why you should spray water in the condenser at 2/3rds
of the charge or once you have completed it. You'll note an immediate pressure
drop when you spray water in the condenser.
To obtain a ballpark high side value, multiply
ambient temperature by 2.2 if you have an R12 system. If you have a factory
R134a system, use 2.3. To convert °C to °F, use this formula: °C
X 1.8 + 32.
Remember: this is only a ballpark. If in doubt,
we have factory charts to help you determine the correct pressures. Please have
your vehicle's make, model, refrigerant type, and year and click
Factors like a an obstructed or very dirty radiator
and condenser, weak or inoperative fan clutch, weak or inoperative radiator
fan(s), either electric or mechanical, will make pressures go up and impair
cooling, even in mild days.