1973 OPEL GT-R air conditioning

REFRIGERANT COMPONENTS
ALL MODELS
CONTENTS
Subject
DESCRIPTION AND OPERATION:
FundamentalPrinciplesofRefrigeration..................
Description of Air Conditioning Components
..........DIAGNOSIS:
GeneralInformation..........................................................
Leak Testing
System1........................................................
Functional Testing System............................................
DiagnosisGuide..................................................................
MAINTENANCE AND ADJUSTMENTS:
General Service Information and
Safety Precautions;........................................................
Charging
andDischargingSystem..............................
AddingOiltotheSystem................................................
Flushing the System........................................................
MAJOR REPAIR:
Removal and Installation Compressor
Opel1900.Manta........................................................
GT
........................................................................................
Removal and Installation Condenser
Receiver-Dehydrator
Assembly
- GT.................................................................
Receiver-Dehydrator
.Opel 1900.Manta................GT..................................................
Removal and Installation Evaporator and
Expansion Valve
- Opel 1900.Manta....................
GT......................................................
Disassembly and Reassembly of Clutch Drive
Plate
andShaftSeal....................................................
Disassembly and Reassembly of Pulley Assembly
and Coil and Housing Assembly..............................
Disassembly and
Reaissembly of Internal
Parts of Compressor and Leak Testing
Compressor..............................................................................
SPECIFICATIONS:
Specifications........................................................................Page No.
9B-18
98-33
98-38
98-39
98-39
90-40
98-41
98-41
9B-47
98-48
98-48
98-56
98-62
90-4990-58
98-52
98-59
98-63
98-67
98-69
98-82REFRIGERANT COMPONENTS ALL MODELS
96-17

98.18 1973 OPEL SERVICE MANUAL
DESCRIPTION AND OPERATION
FUNDAMENTAL PRINCIPLES OF REFRIGERATION
We all know what air conditioning does for us, but
very few understand how or why it works. An air
conditioner is functionally very similar to a refrigera-
tor, so let’s take a look at refrigeration. A refrigerator
is a simple mechanism which, surprisingly enough,
works quite a bit like a tea-kettle boiling on a stove.
That may sound far-fetched, but there is more
similarity between the two than most of us would
suspect. In fact, a modern refrigerator can make ice-
cubes and keep food cool and fresh only because a
liquid called the refrigerant boils inside the freezer.
Of codrse everyone knows a boiling tea-kettle is
“hot” and a refrigerator is “cold”. However, this is
where most of us are apt to get confused. We usually
think of “cold” as a definite, positive condition. Ac-
tually though, there is no such thing as “cold”. The
only way we can define it is in a rather negative sort
of way by saying “cold” is simply the lack of heat
just as darkness is the lack of light. We can:t make
things cold directly. All we can do is remove some
of the heat they contain and they will become cold
as a result. And that is the main job of any ice-box
or refrigerator. Both are simply devices for removing
heat.
All substances contain some heat. Theoretically, the
lowest temperature that any substance could obtain
is 459 degrees Fahrenheit below Zero. This may be
called “Cold”, and anything warmer than this con-
tains heat. Since man has never succeeded in getting
all the heat out of an object, we must think about the
transfer of heat from one object to another when
talking about controlling temperatures.
Figure
96-1 Transfer of Heat
Transfer of HeatThe only thing that will attract heat is a colder ob-ject.
:Like water, which always flows down-hill, heat
always flows down a temperature scale
- from a
warm level down to a colder one. When we hold our
hands out toward the fireplace, heat flows from the
hot fire out to our cold hands (Fig.
9B-1). When we
make a snowball, heat always flows from our warm
hands to the colder snow. In an ice-box, the ice al-
ways is colder than the stored food, so heat naturally
is drawn out of the warm food by the colder ice.
Measurement of HeatEveryone thinks he knows how heat is measured.
Thermometers are used in most: homes. Whenever
we speak of temperature from now on, we will mean
Fahrenheit. They can tell how hot a substance is, but
they can’t tell us everything about heat.
Figure
98-2 Applied Temperature Alone is Not the
Sole Measurement of Heat
When we put a tea-kettle on a stove, we expect it to
get hotter and hotter until it finally boils. All during
the process, we can tell exactly how hot the water is
by means of a thermometer (Fig.
9B-2). However,
our thermometer will show us that the flame is just
as hot when we first put the tea-kettle on the stove
as it is when the water finally boils. Why doesn’t the
water boil immediately then? Also, why does it take
longer to boil a quart of water than a cupful? Obvi-
ously temperature isn’t the only measurement of
heat.
Even though heat is intangible, it can be measured by
quantity as well as intensity. It is recognized that
thermometers indicate only the intensity of heat. The
unit for measuring quantity of heat is specified as
that amount necessary to make 1 pound of water 1
degree warmer (Fig.
9B-3). We call this quantity of
heat a British Thermal Unit. Often it is abbreviated
to Btu.
Perhaps we can get a better idea of these two charac-

REFRIGERANT COMPONENTS ALL MODELS9s. 19
Figure 98.3 Effect of One B.T.U. on One
Pc’und of
water
teristics of heat if we think of heat as a sort of color-
ing dye. If we add one drop of red dye to a glass of
water, it will turn slightly pink. Another drop will
make the water more reddish in color (Fig.
9B-4).The more drops of dye we add, the redder the water
will get. Each drop of dye corresponds to 1 Btu and
the succeedingly deeper shades of red are like in-
creases in temperature.
Figure
98-4 Addition of B.T.U. Heats Water
It may seem a little puzzling to talk about beat in a
story on air conditioning but, when you stop to
think about it, we are handling heat exclusively. Al-
though we ordinarily think of an air conditioner as
a device for making air cold, it doesn’t do that di-
rectly. What it does is take heat away from the in-
coming air and transfer that heat outside the vehicle.
We know now that cold is nothing more than the
absence of heat, and that heat always flow from a
warm object to a colder one. We also have
:a clearer
idea of how heat is measured.
From everything we’ve learned about heat
EO far, it
seems to behave in a perfectly normal manner. Yetsometimes heat will disappear without leaving a sin-
gle clue.
Ice vs. Water for CoolingEtery once in a while in the old days, the ice-man
would forget to refill the ice-box. Occasionally, as the
last sliver of ice melted away, somebody would come
up with a bright idea. He would remember that the
water in the drain-pan always felt ice-cold when he
had emptied it other times. So, he would get the
thermometer out and check its temperature. Sure
enough, it usually was about as cold as the ice. Why
not put the drain-pan back in the ice compartment
to keep things cold until the iceman returned the
next day
It was a good idea. but it never worked. For some
strange reason the ice-box never stayed cold. The
drain water soon got quite warm and in a couple of
hours, the butter in the ice-box would begin to melt,
the milk would start to sour, and the vegetables
would wilt.
Why did this happen? The drain water was only a
few degrees warmer than the ice yet it didn’t draw
nearly as much heat out of the stored foods. How-
ever, the difference between the behavior of cold
drain water and ice is the real secret as to how any
refrigerator works and we can easily learn the an-
swer by using an ordinary thermometer.
When we put a drain pan full of cold water into the
ice compartment, we expect the heat to flow from the
warm foods to the colder water. Remember, that
heat always flows from a warm object to a colder
object and when we add heat to water, it gets
warmer. Each Btu of heat added to a pound of water
makes it one degree warmer.
Figure 98.5 Melting Ice Remains at 32 Degrees

REFRIGERANT COMPONENTS ALL MODELSSE- 21
about heat instead of refrigeration. But in doing so,
we have learned how a simple ice-box works. It’s
because the magic of latent heat of fusion gives ice
the ability to soak up quantities of heat without get-
ting any warmer.
Therefore, since it stays cold, it can continue to draw
heat away from stored foods and make them cooler.
The latent heat of vaporization can be an even better
“magnet” because it will soak up even more heat.
Whenever we think of anything boiling, we instinc-
tively think of it being very hot. However, that’s not
true in every case. Just because water
boi1.s at 212
degrees doesn’t mean that all other substances will
boil at the same temperature. Some would have to be
put into a blast furnace to make them bubble and
give off vapor. On the other hand, others will boil
violently while sitting on a block of ice.
And so each substance has its own particular boiling
point temperature. But regardless of whether it is
high or low, they all absorb unusually large quanti-
ties of heat without getting any warmer when they
change from a liquid into a vapor.
Consequently, any liquid that will boil at a tempera-
ture below the freezing point of water, will make ice
cubes and keep vegetables cool in a mechanical re-
frigerator.
Figure
9B-10 Simple R-12 Refrigerator
Refrigerant - 12Refrigerant-12 is used in the air conditioning system
and boils at 21.7 degrees below zero. Maybe that
doesn’t mean very much until we picture a flask of
R-12 sitting at the North Pole boiling away just like
a tea-kettle on a stove. No one would dare pick up
the flask with his bare hands because, even though
boiling, it would be so cold and it would be drawing
heat away from nearby objects so fast that human
flesh would freeze in a very short time. If we were toput a flask of R-12 inside a refrigerator cabinet, it
would boil and draw heat away from everything sur-
rounding it (Fig.
9B-10). So long as any refrigerant
remained in the flask, it would keep on soaking up
heat until the temperature got down to 21.7 degrees
below zero.
Now we can begin to see the similarity between a
boiling tea-kettle and a refrigerator. Ordinarily we
think of the flame pushing heat into the tea-kettle.
Yet, it is just as logical to turn our thinking around
and picture the tea-kettle pulling heat out of the
flame. Both the tea-kettle and the flask of refrigerant
do the same thing they draw in heat to boil
although they do so at different temperature levels.
There also is another similarity between the ice-box
and the mechanical refrigerator. In the ice-box, wa-
ter from melting ice literally carried heat out of the
cabinet. In our simple refrigerator, rising vapors do
the same job.Rdsing
Our R-l 2Water is so cheap that we could afford to throw it
away. But R-12, or any other refrigerant, is too ex-
pensive just to let float away into the atmosphere. If
there was some way to remove the heat from the
vapor and change it back into a liquid, it could be
returned to the flask and used over again (Fig. 9B-
11).There is a way, and that is where we find the biggest
difference between the old ice-box and the modern
refrigerator. We used to put in new ice to replace that
lost by melting. Now we use the same refrigerantover and over again.
Figure 9B-1 1 Re-Using Refrigerant

9B-22 1973 OPEL SERVICE MANUAL
We can change a vapor back into a liquid by chilling
it, or do the same thing with pressure. When we
condense a vapor we will find that the heat removed
just exactly equals the amount of heat that was neces-
sary to make the substance vaporize in the first place.
At last the lost is found! The latent heat of vaporiza-
tion the heat that apparently disappeared when
a liquid boiled into a vapor again reappears on
the scene when that same vapor reverts back into a
liquid. It is just like putting air into a balloon to
expand it and then letting the same amount of air out
again to return the balloon to its original condition.
We know that any substance will condense at the
same temperature at which it boiled. This tempera-
ture point is a clear-cut division like a fence. On one
side, a substance is a liquid. Immediately on the
other side it is a vapor. Whichever way a substance
would go, from hot to cold or cold to hot, it will
change its character the moment it crosses over thefence.But pressure moves the fence! Water will boil at 212
degrees under normal conditions. Naturally, we ex-
pect steam to condense at the same temperature. But
whenever we put pressure on steam, it doesn’t! It will
condense at some temperature higher than 212 de-
grees. The greater the pressure, the higher the boiling
point and the temperature at which a vapor will
condense. This is the reason why pressure cookers
cook food faster, since the pressure on the water
permits it to boil out at a higher temperature. We
know that R-12 boils at 21.7 degrees below zero. A
thermometer will show us that the rising vapors,
even though they have soaked up lots of heat, are
only slightly warmer. But the vapors must be made
warmer than the room air if we expect heat to flow
out of them. Also, the condensing point temperature
must be above that of room air or else the vapors
won’t condense.This is where pressure comes to the rescue. With
pressure, we can compress the vapor, thereby con-
centrating the heat it contains. When we concentrate
heat in a vapor that way, we increase the intensity of
the heat or, in other words, we increase the tempera-ture;because temperature is merely a measurement
of heat intensity. And the most amazing part of it all
is that we’ve made the vapor hotter without actually
adding any additional quantity of heat (Fig.
9B-12).
Use of Pressure in RefrigerationBecause we must live by press&s and gauges in air
conditioning work, the following points are men-
tioned so that we will all be talking about the same
thing when we speak of pressures.
All pressure, regardless of how it is produced, is
measured in pounds per square inch (psi).Figure 98.12 Compressing a Vapor Concentrates its
HeatAtmospheric Pressure is pressure exerted in every
direction by the weight of the atmosphere. At higher
altitudes air is raritied and has less weight. At sea
level atmospheric pressure is 14.7 psi.
Any pressure less than atmospheric is known as a
partial vacuum or commonly called a vacuum. A
perfect vacuum or region of no pressure has never
been mechanically produced. Gauge pressure is used
in refrigeration work. Gauges are calibrated in
pounds (psi) of pressure and inches of Mercury for
vacuum. At sea level
“0” lbs. gauge pressure is
equivalent to 14.7 lbs. atmospheric pressure. Pres-
sure greater than atmospheric is measured in pounds
(psi) and pressure below atmospheric is measured in
inches of vacuum. The “0” on the gauge will always
correspond to the surrounding atmospheric pressure,
regardless of the elevation where the gauge is being
used.
Basic Refrigerator OperationWe’ve now covered all the ground-rules that apply to
refrigeration. Most likely they still are a little hazy,
but it is easy enough to remember these main points.
All liquids soak up lots of heat without getting any
warmer when they boil into a vapor, and, we can use
pressure to make the vapor condense back into a
liquid so it can be used over again. With just that
amount of knowledge, here is how we can build a
refrigerator.
We can place a flask of refrigerant in an ice-box. We
know it will boil at a very cold temperature and will
draw heat away from everything inside the cabinet
(Fig. 9B-13).
We can pipe the rising vapors outside the cabinet and
thus provide a way for carrying the heat out. Once

REFRIGERANT COMPONENTS ALL MODELS96.23Figure 96-l 3 Basic Refrigerant Circuit
we get the heat-laden vapor outside, we can com-
press it with a pump. With enough pressure, we can
squeeze the heat out of “cold” vapor even in a warm
room. An ordinary.radiator will help us get rid of
heat.
By removing the heat, and making the refrigerant
into a liquid, it becomes the same as it was before, So,
we can run another pipe back into the cabinet and
return the refrigerant to the flask to be used over
again.
That is the way most mechanical refrigerators work
today. Now, let’s look at an air conditioning unit to
see how closely it resembles the refrigerator we have
just described.
Basic Air ConditionerWhen we look at an air conditioning unit, we will
always find a set of coils or a tinned radiator core
through which the air to be cooled passes. This is
known as the “evaporator” (Fig.
9B-14). It does the
same job as the flask of refrigerant we
spok.e about
earlier. The refrigerant boils in the evaporator. In
boiling, of course, the refrigerant absorbs heat and
changes into a vapor. By piping this vapor outside
the car we can bodily carry out the heat that caused
its creation.
Once we get vapor out of the evaporator, all we haveFigure 98.14 Evaporator Assembly
to do is remove the heat it contains. Since heat is the
only thing that expanded the refrigerant from a liq-
uid to a vapor in the first place, removal of that same
heat will let the vapor condense into a liquid again.
Then we can return the liquid refrigerant to the
evaporator to be used over again.
Actually, the vapor coming out of the evaporator is
very cold. We know the liquid refrigerant boils at
temperatures considerably below freezing and that
the vapors arising from it are only a shade warmer
even though they do contain quantities of heat.
Consequently, we can’t expect to remove heat from
sub- freezing vapors by “cooling” them in air tem-
peratures that usually range between 60 and 100
degrees heat refuses to
flow from a cold object
toward a warmer object.
But with a pump, we can squeeze the heat-laden
vapor into a smaller space. And, when we compress
the vapor, we also concentrate the heat it contains.
In this way, we can make the vapor hotter without
adding any heat. Then we can cool it in compara-
tively warm air.
That is the only responsibility of a compressor in an
air conditioning system (Fig.
9B-15). It is not in-
tended to be a pump just for circulating the refriger-
ant. Rather, its job is to exert pressure for two
reasons. Pressure makes the vapor hot enough to
cool off in warm air. At the same time, the compres-
sor raises the refrigerant’s pressure above the con-
densing point at the temperature of the surrounding
air so it will condense.
As the refrigerant leaves the compressor, it is still a
vapor although it is now quite hot and ready to give
up the heat that is absorbed in the evaporator. One
of the easiest ways to help refrigerant vapor dis-
charge its heat is to send it through a radiator- like
contrivance known as a condenser (Fig. 9B-16).
The condenser really is a very simple device having
no moving parts. It does exactly the same job as the
radiator in a typical steam-heating system. There,
the steam is nothing more than water vapor. In pass-
ing through the radiator, the steam gives up its heat
and condenses back into water.
The same action takes place in an air conditioning

9B-24 1973 OPEL SERVICE MANUAL
Figure 9B-15 Compressor Assembly - GT Shown
Figure 3B-16 Condenser Assembly
condenser. The refrigerant vapor gives up its heat,
which is quickly and easily radiated into the sur-
rounding air through the large finned surfaces of the
condenser. In giving up its heat, the refrigerant vapor
condenses back into liquid which collects in a pool
at the bottom of the condenser.
As we have said before, when the refrigerant con-
denses into a liquid, it again is ready for boiling in the
evaporator. So, we can run a pipe from the condenser
back to the evaporator.
Main Units of the SystemThese three units then; the evaporator, the compres-
sor, and the condenser are the main working
parts of any typical air conditioning system. We have
the evaporator where the refrigerant boils andchanges into a vapor, absorbing heat as it does so. We
have the pump or compressor to put pressure on the
refrigerant so it can get rid of its heat. And we have
a condenser outside the car body to help discharge
the heat into the surrounding air.
Pressure and FlowThere is one more unit that co-operates with thesethree. It doesn’t do any real work, but it does act as
sort of a traffic officer in controlling the flow of the
refrigerant through the system. To get a better idea
of what this does. let’s first do a li,ttle exoerimentine
with an ordinary’ tire pump.
When we use a
t,ire pump to Sate an automobile
tire, we are creating pressure only because we are
“pushing” against the air already entrapped inside
the tire. If you question this, just try pumping up a
tire that has a large puncture in it. You could pump
all day, and still not be able to build up any pressure.
As fast as you would pump the air in, it would leak
out through the puncture.
Abou~t all you would be
doing would be circulating nice fresh air through the
tire.
1Jnless you have something lo push against - to
block the tlow of air
- you can’t create more than a
mere semblance of pressure.
The same situation holds true in an air conditioning
system. The compressor can pump refrigerant vapor
through the system, but unless it has something to
push against, it cannot build up pressure. All the
compressor would be doing would be to circulate the
vapor without increasing its
pres,sure.Yet we can’t just block the flow through the system
entirely. All we want to do is put pressure on the
refrigerant vapor so it will condense at normal tem-
peratures. What’s more, this
musi: be done some time
after the vapor leaves the evaporator and before it
returns again as a liquid. We can’t have high pressure
in the evaporator because that would slow down the
boiling of the refrigerant and thus penalize the re-
frigerating effect.
Controlling Pressure and FlowPressure and flow can be controlled with a float
valve, or with a pressure-regulating valve. They do
the same job, but in a different way.
Since the float valve type will give us a better idea of
pressure and flow control, let’s look at it first (Fig.
9B-17).It consists simply of a float that rides on the surface
of the liquid refrigerant. As the refrigerant liquid
boils and passes off as a vapor, naturally the liquid
level drops lower and lower. Correspondingly, the
float, because it rides on the surface of the refriger-
ant, also drops lower and lower as the liquid goes
down.By means of a simple system of mechanical linkage,
the downward movement of the float opens a valve
to let refrigerant in. The incoming liquid raises the
fluid level and, of course, the float rides up with it.
When the surface level of the refrigerant liquid re-
aches a desired height, the float: will have risen far

REFRIGERANT COMPONENTS ALL MODELS9B- 2596.15
Figure 95.17 Float Type Flow Valve
enough to close the valve and stop the flow of refrig-
erant liquid.
For the sake of simplicity, we have described the
float and valve action as being in a sort of definite
wide open or tight shut condition. Actually, though,
the liquid level falls rather slowly as the refrigerant
boils away. Likewise, the float goes down gradually
and gradually opens the valve just a crack. New
refrigerant liquid barely seeps in through the
“cracked” valve. At such a slow rate of flow, it raises
the liquid level in the evaporator very slowly.
With that in mind, it is easy to see how it would be
possible for a stabilized condition to exist. By that,
we mean a condition wherein the valve would be/
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W-16opened barely enough to allow just exactly the right
amount of refrigerant liquid to enter the freezer to
take the place of that leaving as a vapor.
Thermostatic Expansion ValveAutomotive air conditioning systems use a thermo-
static expansion valve in place of the float system.
Figure 9B-18 shows a cross-section of the valve
which consists primarily of the gas-filled power ele-
ment, body, actuating pins, seat and orifice. At the
high pressure liquid inlet is a tine mesh screen which
prevents dirt, tilings or other foreign matter from
entering the valve orifice.
When the valve is connected in the system, the high
pressure liquid refrigerant enters the valve through
the screen from the receiver-dehydrator (which acts
as a storage tank for the condensed refrigerant as it
leaves the condenser) and passes on to the seat and
orifice. Upon passing through the orifice the high
pressure liquid becomes low pressure liquid. The low
pressure liquid leaves the valve and flows into the
evaporator core where it absorbs heat from the
evaporator core and changes to a low pressure vapor,
and leaves the evaporator core as such. The power
element bulb is clamped to the low pressure vapor
line just beyond the outlet of the evaporator (Fig.
9B-20).The operation of the valve is quite simple. It is a
matter of controlling opposing forces produced by a
spring and the refrigerant pressures. For example:
The pressure in the power element is trying to push
the seat away from the orifice, while the spring is
trying to force the seat toward the orifice. These
opposing pressures are established in the design of
the valve so that during idle periods, i.e. when the
system is not operating, the spring force and the
refrigerant pressure in the cooling coil are always
Figure 9B-18 Thermostatic Expansion Valve
Figure
98.20 Expansion Valve Bulb Location