1. Driving Impressions (since this is what everyone wants to know, I put it first)
3. XKE Series II Air Conditioning: History
4. How Automotive A/C systems work
5. Rebuilding the system: Compressor, condensor, and receiver/dryer
6. Rebuilding the system: Underdash unit
8. Recharging
9. Adjustments
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1. XKE Series II A/C: Driving Impressions
The US East Coast tends to be very hot and muggy in the summer. This weekend was no exception, with temperatures in the low 90's and moderate to high humidity. It was a good weekend to try out my brand new, factory fresh XKE A/C.
The first thing I should point out is that the Series II A/C plenum has five vents. Four of them are on the passenger side. So right off the bat, air distribution is uneven.
Second, the A/C unit draws all it's input air from the footwell area on the passenger side. The only way to add fresh air is to open a window or run the heater blower.
Third, those of you who are old hands with E-Types are used to placebo switches. The A/C unit adds two knobs which do almost nothing. One of these is a thermostat knob. This regulates the temperature of the evaporator, not the car interior. The only correct position for this knob is full cold. The other switch controls the A/C fan. It has four settings: low, medium, high, and off. Turning the fan on also causes the compressor clutch to engage, and turns the radiator fans on (rgardless of input from the 'otter' switch). In other words, it turns the unit on and off.
So how does all this work? Fair is the word that comes to mind. The low fan setting is almost useless, so I bounced around between high and medium. Cooling was sufficient to make a hot day bearable, but not really comfortable. I would guess that this unit can drop cockpit temperature by not more than 15 degress (F).
I kept the heater air flap open, and experimented with opening the window a crack vs. running the heater fan to bring in fresh air. Either works. Running th A/C without fresh air will eventually result in a very stuffy cabin.
The battery was slightly on discharge until the engine reached about 1200RPM. With the headlights on, 'on charge' does not occur until over 2000RPM. I am running the 45 amp alternator.
Engine temperature was dead steady just below the middle of the guage. They really did a good job of redesigning the cooling system on the Type II's.
There was little or no effect on gas mileage. This is really not surprising: open windows have about the same effect on aerodynamics as open parachutes. My gas mileage was consistently 14-15 mile per (US) gallon.
Overall impression: it's better than nothing, but the output is disappointing.
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2. Scope of the Project
My car is a 1969 E Type 2+2. It had originally had the factory A/C system, but this had been disabled by the PO. Specifically, the hoses had been cut away to make room for a header system (which I have since replaced with a stock exhaust). Cutting the hoses in this manner allowed all sorts of dust, oil, and water into the system. The compressor, in partucular, was badly fouled. This was my evaluation of the system:
Hoses: Two totally missing, two cut to the
stubs, leaving only the ends.
Condensor: Salvagable, but hard to clean
Receiver/Dryer: Must be replaced, as standard
practice for any A/C rebuild
Compressor: Badly fouled, since isolation
valves had been removed
Underdash components: Facia damaged, mechanical
components condition unknown
The only part available off the shelf for this car is the receiver/dryer. I bought this from Welsh.
The hoses and isolation valves needed replacing, but I had no idea what the hose lengths were. In some cases, I wasn't even sure of the fitting sizes and thread specs. Luckily, I found someone with a parts car, who swapped me the compressor, isolation valves, and hoses for some other spares. The only parts which I would eventually use would be the isolation valves.
I sent the hoses to Old Air Products to be copied.
As to the rest of the system, I lucked into an estate sale which included a carload of NOS Jag parts. This included a brand new compressor and condensor. It also contained a professionally rebuilt underdash unit, sans the facia. The price was surprisingly low, and I was in business.
After six months of parts hunting, the project was now relatively simple.
Rather than bother with old components, I was going to replace everything.
I would have possibly the only 'new' XKE air conditioning system on the
planet.
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3. XKE Series II air conditioning: a history.
The Jaguar E-Type sold to a sports/luxury crowd in the
US. The competion included
Corvettes an Thunderbirds, either of which could be had with A/C. Jaguar
saw it's competion as Aston, Ferrari, and Lamborghini, which all had a
sporting, as opposed to a luxurious character. The English summer climate
is also much milder than in the US, which prejudiced the designers. American
dealers soon became frustrated with Coventry's inability or unwillingness
to supply A/C, and began installing A/C units themselves (see photo and
discussion, p 387 of Porter's Definitive History).
Jaguar was thus pressured by the American dealers to offer A/C in the E Type. Exactly when this became available as a factory option is unclear. Skilleter reports that A/C was available as an option in the 3.8 liter Series I, but this seems unlikely. The discussion in Porter suggests that the factory began development in 1966, and the first units may have been fitted to the 4.2 Series I. But it is more likely that the first 'official' installations were on Series 1.5's, and mass production did not begin until the Series II.
Series II (and Series I, if there is such a thing) air conditioning was an American phenomenon. It does not appear to have been available in RHD form.
How common is it? Hard to say, but there were about 8000 LHD coupes and 2+2 Series II's. When I was shopping, I saw A/C on about 1 in every three cars. This would suggest that a total of about 2400 cars were so equipped. Just a guess.
Judging by the design of the unit, I would guess that these were all built 'off the line', perhaps even being fitted out by the dealer. I base this assessment on the simple design of the evaporator unit, which doesn't provide for outside air, but instead only recirculates inside air. This simple type of unit is very conducive to after-market installation. The photos in Haddock show a large number of variations in part placement and orientation, corroborating my hypothesis.
There are several variations on this unit. I believe mine is the most common.
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4. How an automotive A/C system works
If a gaseous substance is compressed, two things happen: it becomes hot, and it occupies less volume. The relationship of temperature, pressure and volume has been known since the 17th century, and is called Boyle's Law.
A/C systems make use of this phenomenon. A gas (R-12 Freon, in this case) is compressed. In its compressed form, it is then cooled to ambient temperature. Cooled, it condenses into a pressurized liquid. This cooled liquid is then released into a low pressure container. The process now reverses itself: the pressurized liquid evaporates into a vapor and becomes....cold! Warm air from the interior of the car is simply blown across the cold evaporator and viola! Conditioned air.
In theory, almost any gas can be used as a refrigerant. Until the 30's, in fact, refrigerators and freezers used carbon dioxide, amonia, or sulfur dioxide as the refrigerant. Some manufacturers used propane or butane. These gases all have advantages and disadvantages. But the disadvantages include noxious vapors or even explosion in the event of a leak. Dupont's invention of Freon in the thirties revolutionized the refrigeration industry because it was non volatile and almost non-toxic. It also mixes well with mineral oil lubricants used in compessors.
In the 1980's it was discovered that a complex interatction between
freon and other atmoshperic pollutants was destroying the earth's vital
ozone layer. For that reason traditional freons (R12 in particular) have
been severely restricted in recent years. More about this in the section
on recharging.
Lets trace thru the function of an A/C system:
1. Freon is compressed by the belt-driven compressor.
2. Compressed (hot) freon is fed to the condensor via a hose. The condensor is a tube-and-fin device which looks a lot like an auto radiator. It is typically mounted in front of the regular radiator.
3. Air moving thru the fins of the condensor cools the compressed freon, which becomes a fluid.
4. Liquid freon is fed from the condensor to the receiver/drier thru a hose. The purpose of the receiver/drier is, as the name implies, twofold. First, it receives and stages a supply of cooled freon for the evaporator. Second, it contains a chemical substance which absorbs any water from the working gas. This is extremely important, because the fluorine in Freon can react with water to produce hydrofluoric acid, which will destroy the system.
5. Cooled liquid freon is then fed thru a hose from the receiver/drier to the expansion valve. This is a complex little valve which allows the compressed fluid to enter the low pressure evaporator in a controlled manner. It is the 'gatekeeper' betweeen the high and low pressure areas of the system. The expansion valve is typically brazed or welded directly into the evaporator assembly.
6. As liquid freon passes thru the expansion valve, it enters the low pressure area of the evaporator. As it does so, it expands and becomes a gas. It also becomes very cold.
7. A fan blows interior air across the outside of the evaporator, creating cool air which is conducted back to the interior of the car.
8. The freon, which has been heated by the action of the fan, is now conducted back to the compressor, where the cycle starts again.
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5. Rebuilding the Type II A/C system: Condensor, Compressor, Reciever/Drier.
Caution: When working with any A/C part, care must be taken not to expose the part to the atmosphere for an extended period. Doing so will allow moisture into the system, which can cause uncorrectable damage. All parts are delivered from the manufacturer or rebuilder sealed, dessicated, and (in some cases) pressurized. Do not remove the temporary seals until you are ready to connect the parts. If you are reusing an old part, an attempt should be made to dry it. This can be done either by heating the part, or by sealing the part overnight in a plastic bag with some silica gel packets (like you find packed with electronic gear).
Condensor. The condensor on the E-type is a very simple unit. Two short bolts hold it to the front of the radiator, and two straps at the bottom hold it to the front rail. The upper fitting connects to a hose leading to the discharge side of the compressor. The lower fitting connects to a hose leading to the 'in' side of the Receiver/Drier. The only special precaution is to make sure that there is enough clearance to close the bonnet once the hoses are connected. Test the fit very carefully, and bend the end of the tubing if the fit is not good.
Compressor. The compressor on most Series II's is a York Tecumseh. This is a compact little compressor. It is also very much obsolete. I am told that when these things go, they are often unrebuildable, which is just as well, since I have no idea where to get a rebuild kit. As delivered from the factory, there is a full charge of 11 ounces of oil in the compressor. It is also shiped sealed and pressurized to prevent the incursion of atmospheric moisture. Since it is unlikely that a new one will ever turn up again, these facts are presented for historical purposes only.
Isolation valves. The input and discharge ports on the compressor connect to hoses via isolation valves. When these valves are turned fully clockwise, the compressor is sealed off from the balance of the system, allowing it to be replaced or maintained independently. When the valves are halfway down, they allow the system to be charged thru the service ports. when the valves are all the way up (fully counter clockwise), the system is in normal operating status. The top of the isolation valves should be canted approximately 45 degrees towards the engine. If you install the valves upright, you will end up with two little bumps on your bonnet. The clearance is that tight.
Mounting bracket. The bracket which holds the compressor is a very heavy duty appliance. It is an L shape arrangement of box steel, which allows the compressor to be mounted where the alternator normally is, and the alternator to be relocated in front of the engines.
Belts. The compressor belt can be changed without removing the alternator or the alternator belt. This may not be obvious at first glance. The procedure I followed is:
- Turn the steering wheel to the right.
- This allows you to 'step in' behind the left front tire, to get a good angle on the work.
- Using a 3/4" open end wrench, loosen the bolt holding the jockey wheel bracket. The engineering here is almost comical: there is exactly enough clearance under the coil to allow movement of the wrench. You undo the bolt one flat at a time.
- using a large adjustable wrench behind the jockey wheel, swing it out of the way. The belt is now loose.
- Slip the belt off the compressor and pulley.
- There is exactly enough clearance to slide the belt out under the L bracket.
- Installation is the reverse of removal.
Receiver drier. The receiver/drier is bolted to the brake fluid heat shield. There may be a few variations on this location. The 'in' side is connected to the lower condensor fitting via a hose. The 'out' side is connected the underdash unit with another hose.
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6. Rebuilding the Type II A/C system: Underdash.
The underdash assembly contains the evaporator, expansion valve, thermostat, fan, and switch. This is all in one fiberglass unit which also serves as the air plenum and condensate drain. This is quite a lot of function in a 30 inch by 10 inch unit.
The evaporator and expansion valve are brazed into a single unit. The large hose connects the unit to the input of the compressor. The small hose connects the unit to the output of the receiver/drier. These hoses feed thru an oblong hole in the firewall. On my car, this hole did not line up with the underdash unit precisely. See my comments above regarding the 'off the line' nature of these air conditioning units. The hoses had to be attached before the unit was hoisted into place, and then it was a struggle hanging the box.
The evaporator sits at the low point of the plastic case, allowing condensate water to drain out through two outlets at the rear of the unit. The drain water then feeds thru two surgical rubber hoses which lead out thru two grommeted holes in the transmission tunnel. The left hose unfortunately drains right on to the exhaust system, which will probably have an effect on the longevity of the front pipes. The handling of condensate water is generally ineffective, and the carpet will be a bit damp after a full day of running the A/C. This is primarily due to condensation around the hose fittings.
The fan unit is integral with the evaporator case. The fan motor projects out the top of the unit, and fits neatly into an 'empty' space behind the glove box.
The front facia is very, very delicate. Mine was in pieces when the car was delivered, and diligent search failed to locate a good replacement. Instead, I built up a jig out of wood and cardboard, and remolded the broken parts as best I could. The louvers on mine all work, but they tend to move around with a mind of their own. The stress of assembly cause additional cracking, which I had to fix in place. If I could think of something better to replace it with, I would.
The unit has two 'tabs' on it's top side. These engage the lower edge of the dashboard. Although this seems flimsy, it is adequate to suspend the unit. Two brackets, one next to the ignition lock, and one on the passenger side kick panel, keep the unit from sliding out back out of the dash.
The ignition lock, by the way, is attached to the side of the A/C unit. The steering column does n_o_t lock on an A/C equipped car.
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7. Electrical System Considerations
A white wire on the battery side of fuse 7 energises the A/C relay. This relay is located behind the left splash panel. The three relays located there are (from the top): horn relay, alternator relay, and A/C Relay.
The relay is energized whenever the key is in the on position. When energized, a high current circuit brings power back to the A/C switch (black wire). There is an in-line fuse on this circuit. I used a 20-amp fuse here (does anyone know the correct rating).
When the A/C fan switch moves to one of the on positions, a second fan relay is energized, turning on both radiator fans. Both fan relays are on a steel plate bolted to the railing directly below the coil. A very large resistor on the brake fluid heat shield modulates the speed of the A/C fan. There are take-offs corresponding to the High, Medium, and Low Speed settings.
Depending on the setting of the thermostat switch, the compressor clutch will also be energized when the A/C fan is turned on.
The wire bundle for all of this passes out the firewall thru the same hole as the evaporator hoses. This doesn't seem like a particularly save arrangement, but there it is.
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Recharging should be carried out by a licensed A/C shop. This is for several reasons.
- You need to get all the air and moisture out of the system before you recharge. Failure to do this will result in premature failure of the system.
- It is illegal for just plain folks to handle R12.
- Professional shops have leak detection equipment, which can save you time and money.
- Guesswork is a poor substitute for manifold guages.
As mentioned before R12 is on the 'endangered substance' list. Now you may have heard about substitutes, but there are really no replacements for R12 yet (1997). Various experimental products are not approved, and the established substitute products are composed of methane, propane, or other noxious/explosive materials. They install the same way as r12, but their chemical properties are all over the board.
A 'minimal modification" will be required to install a substitute coolant. The 'minimal modification' will include, at the very least, replacement of the fill valves. The EPA (in the US) requires that automotive systems have a unique pipe fitting, depending on the type of refrigerant used. This allows proper recycling. You will also need to install barrier hoses (good idea to do this anyway, if your hoses are original).
If the new refrigerant is compatible with mineral oil, fine. Otherwise the system may need to be completely drained and cleaned, before refilling with synthetic lubricant. By the way, the oil seals which worked so well for the last (fill in the blank) years may quickly fail if they are incompatible with synthetics. The A/C shops I've talked to would rather replace the compressor than bother with all this. In fact,if you are doing all of this, you may as well replace everything and convert to R134.
So much for the pitch. How much does it cost? Unbelievably, a full charge of R12 costs $100-$150 in the New York area! Ouch!
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9. Adjustments. The thermostat dial on the dashboard detects the temperature of the evaporator, not the cabin temperature. If you find that you aren't getting enough cool, the chances are that the thermostat capilary has be inserted too far into the evaporator matrix. This can be adjusted without disassembly. If you hold a flashlight to the second vent from the left, you will see the capilary tube. It looks like a piece of aluminum wire. Follow this to the point where it enters the evaporator matrix. Use a crochet hook to pull this back out of the matrix (don't worry, the end that goes into the evaporator is not bolted, tied, or locked down in any way). You should be able to pull this back about half an inch. This will lower the temperature of the cool air about five degrees. That is the only adjustment I know of.