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As we are all getting older and drive our
normal cars with very efficient air-conditioning it
becomes ever less pleasant, particularly during summer,
to drive an English Hot Box where even fresh air inlets
used to be optional in early cars, [The under dash fresh
air door], after 72, the centre console and centre dash
fresh air vents were standard.
2 years ago I completed the A/C of my
C-GT [June 06.] this totally transformed an excessively
hot and noisy car into a proper GT car. We can use the
audio system and go anywhere in great comfort any time
of year, whatever the outside temperature is, hot or
cold, and indeed use the A/C all year round as with the
low sun angle during winter the car still gets warm to
hot. Window tinting is essential because of the low
Winter Sun angle and direct radiation thru the side
windows, a tinted and banded windscreen is useful if you
have to replace a windscreen. 25% tinting is legal in
Queensland for windscreens and 35% for the other glass.
I am not going to write a “Tech Talk”
detailed article on the project but an overview of what
A/C entails, parts, costs, practical considerations etc.
There are several items to be installed,
Evaporator [the unit in the cabin], Condensers 2 for the
“C” & “V8”, 1 for the “B”, Compressor, Receiver/Dryer,
Relays, Fuses, Much Bigger Alternator, and for
completeness throttle compensation and a way to not
allow the system to run until the engine is running.
This is how modern cars work where the A/C is left on
all the time and the system comes up under engine
management control.
Now the nasty part: COST, with insulation
which is essential in both the “B” & “C” if the A/C is
not to fight the engine and exhaust heat. They were
designed as basic Sports Cars and not as Saloons. With
all components, brackets and fittings the whole bloody
shooting match will cost about $4,000, if you do most of
the work yourself other than the A/C plumbing and
gassing of the system. Having the job done by others is
not a practical option as the cost will be a high
percentage of the value of the car in most cases.
The actual A/C is the easy part, what is
tedious and very time consuming is installing the
insulation and this will depend to what extent you want
to go to achieve quietness & coolness, as in a current
A/C car. I took about 7 months total, a mixture of full
time and part time work, with days of up to 6 hours with
the insulation.
I tend to be very old fashioned and
believe in the ancient adage of “If a jobs worth doing
it’s worth doing properly”. So I probably have overdone
it [being me]. In retirement I took this on as a very
interesting project, and it was, it actually took me
back to training school days and to relearning all the
old skills. This 40 year old “Pretty Fast Truck”
[PFT-000] has now become a most interesting hobby, as
well as a very enjoyable GT car, the way it should have
been in the first bloody place. While I was doing the
A/C another “C-GT” owner was following me along on a
“Monkey see, Monkey do” basis and he spent a lot less
time doing his car, but didn’t go to nearly the same
extent with the insulation. A different type of
insulation could cut the time by months if only heat
insulation is required. I went for a Thermal and
Acoustic approach.
In our “C” we have about the same
conditions as in our BMW 325i Coupe, as regards coolness
and a quiet cabin below 90 Kph. We can listen to
classical and jazz music as long as we are doing 100 Kph
or less, above this speed the wind noise dominates and
we can do nothing about that. Ancient thinking and
design dominate.
All the components are from the “JAY AIR
Automotive Air Conditioning Catalogue”. Don’t bother to
even think of parts from the wreckers as it is a total
false economy. A/C parts have to be new and clean with
no corrosion, moisture or wear to get long term reliable
service.
The component parts and model numbers are
as follows:
2 250mm by 250mm by 30mm,
Condensers. Part # CN5042.
2 Pusher Fans 225mm. [6.8 Amps
each]. Part # EF3527.
1 Evaporator. [mounted under glove
box]. Part # EV1401.
1 Soft Start Vane Compressor, Seiko
Seiki. Part # PM3111.
1 Receiver/Dryer and Binary
pressure switch. Common
Part.
2 Eyeball
Vents. Part
# LV0478.
1 65 Amp Alternator. The A/C system
draws up to 29 Amps.
1 Vacuum Motor and Solenoid Vacuum
switch.
1 Oil Pressure switch. Normally off,
on with oil pressure.
2 30 Amp relays. use “Bosch” as they
are reliable.
1 Lucas copy fuse box, similar to
the existing fuse box.
For cars without a centre console as
fitted to 72/73 cars you need to get the centre console
[2 components], 2 dash fresh air vents, which are all
now available. The vents fit into the place where the
Radio normally mounts. The Radio now lives in the centre
console.
In the “C” and “V8” there is either no
space and or too much heat to mount a single condenser
in the engine bay. These cars do not need any more heat
or obstruction to the radiator air flow. With an MGB- GT
a single condenser can be fitted in front of the
radiator as there is lots of space and engine conditions
will tolerate mounting in the engine bay.
For the “C” and “V8” two condensers are
used, these mount in the wings below the headlight bowl,
there is space with either the standard valence or the
later air dam so the external appearance is not
affected. Slots are cut in the valence to give plenty of
air to the fans and unload the fan motors at cruise. In
our car we discovered that they also give brake cooling
which is a great benefit.
Inside the cabin the Map Pocket has to be
removed to allow the Evaporator to mount as it is a very
nice fit between the centre trim and outside trim. In
our car we have mounted the Map Pocket on the vertical
panel under the “Kiddy” seat, central behind the
passenger seat. This allows the driver to actually get
things out of the pocket while in a seat belt. The
“dopey” bloody poms never thought of this. In the case
of the “C” they seemed to NOT consider lots of things.
To operate the fresh air door [behind the centre
metalwork] I added a push-pull rod and a bracket next to
the console so the driver can operate the fresh air door
while driving the car. You have to do this otherwise you
cannot operate the fresh air door as the feed tubes to
the centre and right hand side block access to the
operating lever.
In the “C” the windscreen washer
container moved up next to the heater between the heater
and brake booster, the windscreen washer motor [Part #
GWW125] mounts inside an opening in the inner wing,
along with the solenoid/vacuum switch. A 2 litre food
container becomes the new washer bottle [original one is
1.75 litres].
The radiator overflow tank moves to where
the windscreen washer container was. The relays and
additional fuse box mount over near where the fuse box
is fitted.
In our “C” the compressor mounts onto the
timing cover and block and takes the space where the
overflow tank was, the threaded mounting holes are
already in the block as are the holes in the timing
cover. A Japanese pulley is mounted onto the harmonic
balancer, to suit the compressor pulley, on our car the
drive pulley to compressor pulley is 1.23:1 step up as
the “C” idles @ about 800 RPM.
For the MGB-GT and MGB-GT V8 you will
have to sort these mountings out yourself as well as how
to mount the compressor and it’s driving pulley. The
compressor has a double pulley so it could be used as an
idler/transfer pulley to drive the alternator from the
compressor. I would look to see how to drive the
compressor from the crankshaft rather than use the
transfer idea. The commercially air-conditioned MGB-GT’s
mounted the compressor where the alternator was and then
drove the alternator, mounted above the compressor, with
a separate belt from the compressor pulley.
I started with a 43 Amp alternator which
worked fine but was limited in traffic with A/C, Lights
[100/55 Watt Halogen], and Radio. The “C” and “V8” run
at such low revs in traffic that 43 Amps was on the low
side. The 65Amp unit will handle everything from idle. I
changed the alternator pulley ratio from 1.875:1 to
2.1:1 at the same time, as our car will run happily @
1,000 RPM in top and 1,100 RPM in O/D, the “V8” will be
similar.
Mounting of the Receiver/Dryer can be
almost anywhere in the line from the condensers to the
Evaporator, in our car it goes behind the radiator
mounting panel on the left side, just in front of the
compressor drive pulley. There is not much spare space
in the engine bay now. I can, and have, removed the
engine and transmission with the A/C system intact by
tying the compressor over to the inner wing. I was very
pleased that this was possible. Murphy’s Law almost
guaranteed that I would have to do this and indeed the
rear crankshaft seal failed not long after the A/C
system was finished.
While I had the engine and transmission
out I insulated the firewall on the engine side as well
as the inside of the tunnel [this is where most of the
heat in the cabin comes from]. Cars with a sun roof seem
to be a lot cooler as they can let this built up heat
out. Our car is now cool everywhere even the chrome
ring around the gearlever stays only warm and not very
hot as from the factory, the tunnel ,foot-wells and
floor are all comfortable even after a 300 mile day run
in summer. In winter we leave the A/C on the least cool
setting and add fresh air via the heater [off side] door
in the left foot well. The fresh air door can be opened
to the 1’st and 2’nd positions as required. Position 3,
is not possible as the A/C feed tubes will not allow
this, and if the air door is opened to the 3rd
position it will direct air & dust directly into the top
of the radio. Stick to position 1 & 2 only.
I am happy and willing to talk to club
members and to show what is required on an individual
basis, car by car, as this detailed knowledge cannot be
successfully documented. 1 picture is worth a 1,000
words and there are lots of photos in my A/C files.
Members who would like to see the photos, to get a feel
for the work required, are most welcome to contact me re
a suitable time and date. If you intend to keep your car
for some years this is a most worthwhile thing to do,
the difference is amazing, cool and quiet. I think, but
don’t know, that we have added about 30 to 35 Kilos to
the car, all down low and in the centre which in the
“C’s” case is more of a benefit than a disadvantage. A/C
reduces consumption by only 1 or 2 MPG overall.
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