ALL ABOUT AIR

By Jerry Nuijen

Saturday, Nov 4 was one of those clear, warm fall days that northern California is famous for.  After the wet October we’ve just experienced, it was a welcome change.  A perfect top down, let’s go touring in the Jag kind of day.  Now everybody knows that November can be a wet month, so your club never plans tours for this time of year.  We go indoors and have a tech session.  Right?

(Al DeLong & Pat Shasby)

Well, the tech session at Al DeLong’s famous Jaguar repair facility in Campbell couldn’t have had a more appropriate topic; air conditioning.  Those of us who had one that functioned certainly used it on this fine Saturday.

Al started the session off with a discussion of the basics of how any automobile air conditioning system works.  He likened it to a small, apartment-sized refrigerator with the door open and a fan blowing cool air from the interior.  He talked about how long and reliably refrigerators run (up to 30 years without any maintenance) and how short and unreliable the life of an auto air conditioner can be (as little as 4 years).  The reasons for the difference are many.  Refrigerators hardly ever get moved.  They operate in a benign environment where the temperature and humidity on their outside is pretty much constant.  And they operate continuously, so their refrigerant and lubrication are always circulating.  Compare this to the underhood environment in a car.  Everything is moving and vibrating.  The temperature can vary from -20°F to +200°F in a very short period of time.  The system maybe shut down for months at a time, or even worse, it maybe left in a discharged state from the end of Sept. to the middle of May, absorbing moisture and depositing crud because it’s owner says to himself, “I won’t fix it until I need it.  That way I’ll save money.”

Al explained how the compressor circulates the refrigerant from the condenser in front of the radiator to the evaporator that is mounted in unit with the heater under the dashboard.  He had a neat display board with all the components of a 1970 thru 1987 Jag climate control mounted on it in exploded view form.  He emphasized that working on an air conditioning system was not something the average home mechanic should do.  For starters, it is illegal to discharge R-12 (Freon) into the atmosphere.  To do so can get you fined $10,000. Freon must be properly sucked out of the system by a special machine that filters it and recycles it for use again.  Secondly, Freon is dangerous.  It is flammable and gives off a compound similar to mustard gas when it burns.  It can damage your skin on contact and blind you if it gets squirted in your eyes.  Working on a Jaguar system has it’s own set of difficulties.  It’s a two-day operation by a professional to remove and reinstall the evaporator/heat matrix box under the dash.  We’re talking big dollars here.  With parts, the bill could easily top $1500.

After this sobering introduction Dave Osborne, one of Al’s mechanics, took over.  In great detail he explained the function of the compressor itself and its associated thermal and pressure protection devices, the function of the evaporator valve, which senses temperature and pressure at the inlet to the evaporator and lets in more or less refrigerant, the purpose of the receiver/dryer, and the purpose and types of lubricants used in the closed system.  Then he got specific about the Jaguar climate control, explaining how that little hole in the dash over the glovebox door has a temperature sensor inside it, and this, in conjunction with the left knob (temperature) and the amplifier (which is buried on the trans tunnel) tell the servo (behind the right knob, but not directly attached to it) how much to move the air flaps on the evaporator/heater box and when to open and close the water valve in the hose that leads to the heater matrix.  Dave talked about common malfunctions and the probable component causing them.  The amplifier was fingered more than once.  Fans that only run at low and high speed and systems that refuse to regulate the temperature properly no matter how much you fiddle with the temperature knob probably need a new amplifier.  Aftermarket ones are available for $125 and seem to be every bit as good as the dealer item.  Replacing the amplifier is a job the home mechanic can tackle. 

The servo is another component that malfunctions with regularity.  Sometimes it’s just a microswitch out of adjustment or a vacuum hose or wire that has come adrift that prevents the system from cooling the car and sometimes the servo is just worn out and needs replacing (at $300 it might seem expensive, but the newer cars have a computer that fails just as often and it costs $700-800).

The inevitable discussion about R-12 vs. R-134a was launched.  R-12 is no longer manufactured in most parts of the world and the supply in the U.S. is declining rapidly.  Cost has gone through the roof.  Al charges $46.50 per pound (but gives a discount to J.A.G. members ) and a Jag system needs 3 lbs. if it is dry.  The day will soon arrive when it will be illegal to recharge an auto air conditioner with R-12.  So, is it possible to convert to 134a and how much does it cost?  Yes, and it ain’t cheap.  Theoretically, all you need to do is pump out the Freon, drain the oil from the compressor and replace with oil compatible with 134a, put on some new charging fittings and pump in 2 lbs. of R-134a (about $6/lb).  The reality is usually different.  If your system is in good shape (not leaking) you have no reason to convert.  If your system is leaking the fix is expensive and you can’t afford to keep on putting in R-12 at $46.50/lb (besides, it’s illegal to put R-12 into a system that leaks). 

The main sources of leaks are the front seal on the compressor and the hoses.  A brief discussion about the feasibility of repairing a compressor with a leaking front seal got the short answer that it isn’t cost effective and usually doesn’t work anyway.  Good rebuilt compressors cost $200 (don’t waste your time and money on the $99 specials), new compressors cost $485 and hoses cost $45 each.  When you open a system you need to replace the receiver/dryer and the expansion valve, $30 each.  Be very careful when replacing the expansion valve.  Just because it has a big nut on it doesn’t mean you need to apply a lot of torque to it.  If you twist or break the inlet pipe on the evaporator you have to disassemble the dash and remove the heater box and most likely you need to buy a new evaporator at $600.

Dave next addressed the question of how much oil you should add to the system when a component is replaced.  Compressors come with and without their oil charge.  If they come with oil, this charge is sufficient for the compressor and whatever will be deposited in the receiver/dryer and the hoses.  Don’t add oil to the system if you replace the compressor, just make sure the right amount of oil is in the compressor.  As an aside, do not run the compressor until you have a partial charge of refrigerant in the system.  You can damage the internal seals in the compressor.  If you have the old R-12 pumped out and the console doing the recycling separates oil from it, obviously that amount of oil has to go back into the system if you aren’t replacing the compressor.  Typically it will be one or two ounces.

One common problem that isn’t really a system failure is the “water on the feet” syndrome.  The heater/evaporator box has two drainpipes that lead to the underside of the car. When they are clear they drain off the moisture that condenses on the evaporator when it is operating. When you park your car after running the air conditioner you’ll notice a puddle of clear water under it. Unfortunately, leaves and dirt make their way into the box and over time they form a paste that clogs the drains.  The water now backs up and overflows onto the floor, wetting your feet and ruining the carpet.  By taking off the kick panels on the inside of the footwells you can reach the drain hoses and clean them.  Sometimes from underneath the car you can use a wire gently inserted into the drainpipes to clear them.  Run some water into the air inlet near the windshield as you probe the drainpipes.  This problem will occur every 4 to 6 years, depending on how much your car sits outside and how many trees it sits under.

We had a pleasant lunch break thanks to Pat Shasby and Karen DeLong who brought in some delicious poor boy sandwiches and Dick France who supplied the liquid refreshments.

After lunch Roger Thibodeau, the man who mans the air conditioning recharging console took us through the pump-down and recharging of a system that had just been repaired (Bill Earl’s 5 speed XJ6).  The pump-down to a complete vacuum takes about 30 minutes and is followed by a waiting period of a few hours to make sure the system will hold a vacuum.  Then a small charge of Freon is added, the engine is started and a sniffer is run over the system.  Roger uses a very sophisticated sniffer that can detect 2 or 3 parts per million of R-12 or R-134a.  The buzzer was going off continuously.  Roger explained that residual Freon, which is heavier than air, had accumulated near the areas where he had done repairs.  By using an air hose and running the engine the air was cleared and the system pronounced leak free.  Now the rest of the Freon is added and high and low side pressure is monitored until the high side reads about 250 lbs/in²  and the low side reads 30 lbs/in² .

Our group, which included Skip Rice, Dean Spielman, Mickey Jones, Karl Klemmer, Len Stevens, Henry Offer, Rick Whicker, Ed Knox, Norm Christie, Kevin Smith, Bill Price, the stalwarts Dick France and Pat Shasby, and yours truly, broke into smaller discussion groups and we all agreed that maintaining modern Jaguars can be excruciatingly expensive.  If one were to buy a nice older XJ6 or XJS and have to do major repairs on/or conversion of the air conditioning system, the bill could easily be half of what you paid for the car.  Al showed us a 1990 sedan that was in the process of having a blown head gasket replaced and receiving a preventative valve job.  He talked about all the black boxes scattered around these late models and how the post ’94 cars have to be put on a scanner at the dealer because the computer will no longer return error codes that you can read on the dash or with a simple handheld scanner like the kind that Kragen sells.