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Jaguar Repair/my 87 jag takes a long time to heat

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QUESTION: HOWARD; my 87 jaguar 4.2 litre engine takes a long time to heat up inside
the car. i have to turn the temperature wide open to get the heat
to activate. i notice that the middle large air vent does not open
until the heat is at its highest peak.
regards,
richard

ANSWER: Hi Richard,

The Series III AC/Heat system is a automatic climate control system and is complex. The AC is in operation all the time winter and summer and is never off. The control of temperature inside the car is controlled by door blending and the two fans speed.

The control of the door blemding is done by a electric motor powered drum with cams that open and close vacuum valves and electric switches. Under the front lip of the upper dash pad is a hose and sensor to sense inside air temp. There is not just one item involved during any function, so it is a complex system of sensors and feed back pots.

The test sequence just for the vacuum door blending alone is seven pages long. I can tell you that the large center door is never open except on full cool.

There is no test plug for even the dealer to plug into to diagnose the system. The only way I know is to lay the 70 page manual open and start testing the components. Even an AC shop who didn't have that manual would be lost. Even most Jaguar dealers have lost their mechanics who knew the system as the last jag with this system was 26 years ago.

The manual may still be availabe from Jaguar. It was called "Series III Climate Control" and is 70 pages. Another option is the "Series III Service Manual" from Jaguar. That should for sure still be in print.

I can not even attempt to work on my own Ser III AC/heat system without the book laid out in front of me. I'm sure an AC Tech in a dealership back then could do the tests without the book but they would be difficult to find if any are still alive.

Check with your local Jag dealer to see if you can get the AC manual and if you can't, let me know as I still have some contacts that may come up with it.

I can't use this program to run down all the tests necessary to diagnose an AC nor heating problem on the Climate Control system.

Howard

---------- FOLLOW-UP ----------

QUESTION: HOWARD:
THAT SOUNDS LIKE A REAL COMPLICATED AGENDA.
I HAVE THE JAGUAR SERIES 111 SERVICE MANUAL. IF YOU COULD STAY IN TOUCH
WITH ME..MAYBE WE COULD COME UP WITH A PROGRAM THAT WOULD REALLY WORK.
THE BOOK THAT I HAVE IS ABOUT SEVENTY PAGES LONG. THE PROBLEM IS THAT I
AM NOT THAT GOOD AT READING DIAGRAMS OR BLUE PRINTS.
ONCE AGAIN I HAVE THE BOOK........
REGARDS,
RICHARD

Answer
If you had the AC manual, you don't need to at first worry about the wiring diagrams. Just follow the tests on the door blending movements. You will have to remove the dash top and the two side panels to see which door is moved at which time. The series of seven pages of vacuum tests will lead you to which one or ones that are not operating when they are suppose to.

Then when you establish which door or doors are not moving. You then check for vacuum on that vacuum diaphragm (vacuum motor) and then you can check that vacuum switch on the rotating drum and if all is correct up to there then you will have to start testing electrics as the drum is rotated by an electric motor. The four ganged relays in one box on the left side control the two fans so they operate afterward.

The service manual is difficult to follow but it is good to first just read the whole section on AC and heat. This will give you a insite on roughly how it operates. You should still contact your local Jag dealer to see if they can get you the AC manual. It is much different then the service manual and has a more practical approach to testing.

If it is not in print, let me know and I will see if any of my contacts can come up with it.

Howard  

Jaguar Repair

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Howard M. Fitzcharles III

Expertise

Jaguar from the XK 120 to XJ-6 ser. 3 1987

Experience

Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Organizations
Associate member SAE EAA member

Publications
Import Car magazine

Education/Credentials
ASE Master Auto with L-1 certification up to 2000

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