Originally posted by eric1:
Condenser is High side pressure. Relief on r-134a is usually 380 PSI.
Working pressures on the car are in the 150 to 200 PSI range with excursions into 300 psi not unusual.



Okay,

Here is an overview of your AC system in case you wondered how it all worked...

Compressor -> Accumulator(Dryer) -> Evaporator -> Orifice -> Condensor -> Compressor.

Everything between the Compressor and the Orifice is HIGH PRESSURE.
Everything between the Orifice and the Compressor is LOW Pressure.
The Orifice is a very small tube, surrounded by a very fine filter.
This is the only part responsible for the HIGH/LOW side pressures,
and can cause a lot of problems if it is clogged with metal shavings
from a worn out and poorly lubricated compressor.

You should find this valve and replace it if needed.
It is easy to locate, just follow the hose route and somethere where there is a union,
between the evaporator and the condensor, you will see dimples on one side, in the tubing.
The dimples hold the Orifice tube in place.
Open the union and remove the Orifice tube and take a good look at it.
If it is clean and full of oil, then your compressor and AC system is fine.
Then you can just put it back.
If it looks dirty and full of metal grit, like the metal grit in the bottom of a tranny pan,
then you will need to replace your compressor and accumulator.

Now, the parts are named this for their function...
The COMPRESSOR takes the R134a and compresses it, turning it into a LIQUID, and pumping it through the AC Line.
The LIQUID, under HIGH PRESSURE cannot be forced through the Evaporator quickly, so it ACCUMULATES in the Accumulator(or Dryer).
From the Accumulator, the R134a flows into the EVAPORATOR.
The Evaporator is called so because, high pressure R134a enters as LIQUID and leaves as a GAS (evaporates).
The blower fan inside your car draws hot air through the evaporator
and the liquid R134a removes the heat from the air, making the air cold.
The high pressure liquid then turns to a high pressure GAS (EVAPORATING) from the change in temperature.
This GAS then passes through the ORIFICE, which regulates the flow of the gas.
Once through the Orifice, there is a change in pressure.
Now the R134a is a MODERATE PRESSURE HEATED gas.
The R134a, in this state, enters the CONDENSOR.
In the CONDENSOR, the outside airflow, either being drawn by the electric cooling fans,
or flowing through the radiator as you drive, removes the HEAT from the R134a,
that it absorbed when it passed through the Evaporator.
This effectively makes the GAS change from a low density to a HIGH Density gas(CONDENSATION).
This works much like a Intercooler for a Turbo.
Cooling a gas makes the gas higher in density.
This also changes the pressure from moderate to LOW.
A higher density gas takes up less space than a lower density gas.
Now the gas is then drawn into the Compressor, to be pressurized, liquified, and then back around the AC Route again.

Now than you understand how the AC system works, troubleshooting it will be much easier.

Pete... 2004 Mercury Marauder 300A Black Clearcoat/Dark Charcoal LEATHER DOB 10/31/2003 DOP 1/2/2004 www.mercurymarauder.net