Editor's note:
This is NOT a faithful reproduction of the original document.  We have removed or replaced indecipherable images, changed nonsense text and added information.  This document is not finished because we have not yet been able to obtain an unaltered original.  There is also documentation in the Service Manual (AKM9006) that is yet to be incorporated.
Coolng problems not associated with an insufficient charge are usually the result of a failed amplifier because the amplifier was so poorly designed that it is the most common component to fail.  A new amplifier is expensive, but you can obtain a guaranteed used one from everydayxj.com.  Your troubleshooting should first verify that the heater valve works correctly, then that there is sufficient vacuum for it, and finally that, with the compressor engaged, the flaps respond to the temperature setting.  When you switch from defrost to full cool, the flaps MUST open the vents in the dash and close the defroster vents.  While there are reasons other than a failed amplifier for the flaps to misbehave, the amplifier is almost always responsible for the flaps to move to their cooling positions when cooling is called for.
Remember that the A/C cannot overcome the heat introduced from the heater valve, so it must close off the hot water to the unit.

The air conditioning heating system fitted to Mark II models is a climatic control type using two manual controls.  One selects the desired temperature; the other selects mode of operation.

The system can automatically maintain any temperature selected at the temperature selector (65°F - 85°F) by comparing the car's interior temperature with that selected at the manual selector.  The difference in temperature at these two points produces an electronic signal which, through an amplifier to a motor driven camshaft, operates various relays, microswitches, vacuum switches, linkage and flaps programing the unit to automatically cause hot or cold air to flow to the car's interior, depending upon the temperature selector setting.  The camshaft servo motor can be driven in either direction.  The air temperature entering the interior may be hot or cold or an infinitely variable mixture of the two.  The air is introduced into the interior by two four-speed fans and fed through a series of blending flaps which direct it to the evaporator and/or heater cores and then into the car interior.  If quick or slow air distribution of heating or cooling is desired, the automatic fan speed functions can be overridden to provide high or low fan speed.

The low speed fan operates in Auto and LO positions automatically; however, if high or low speed fan is selected, all other functions still remain automatic.

Air into the car's interior is available at both front and rear footwells - center dash face level outlets - end of dash face level outlets and screen outlets, depending upon mode of operation selected.  The dash panel outlets are controllable for quantity and direction of air distribution.

Defrost may also be selected in which case the automatic sensing system is overridden and all air is emitted at high fan speed at the screen outlets with a small bleed to the footwells.  Manual operation of the end of dash panel outlets for side window demisting is optional.

As temperature output is controlled by mixing air of differing temperatures rather than controlling the flow of Freon through the evaporator, some difference in temperature is possible between upper and lower outlets, depending upon the position of the flaps.  This air blending gives a more rapid response to manual control changes and finer selected temperature control.  All air, whether heating or cooling is selected, is passed through the evaporator and dehumidified.

The air flow from the unit is 230 cu.ft./min. on heating, 300 cu.ft./min. on cooling.  By comparison, the Jaguar Mark I air flow was 200 cu.ft.fmin for both cooling and heating.

Cooling capacity of the Mark II is 27300 BthUs/hour, heating 13500 BthUs/hour; whereas the Mark I was 17900 BthUs/hour cooling, 11700 BthUs/hour heating.

Upper and Lower heating flaps and Lower Cooling flap on common linkage - Lower heater flap can be overridden by vacuum actuator - Upper Cooling flap is controlled by arm.

S1002 Page 5 of 88

Location:  Behind L/H console kick panel and in front of main air conditioning relay.

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Location:  Under hood on bulkhead behind engine.

Location:  Behind L/H console kick panel and above main air conditioning Relay.  RTC684

Function:  Activates screen outlet actuators (flaps open) in defrost mode, also closes lower heater flap by overriding linkage.                     

Location:  On right-hand side and behind console panel mode control switch.  '70'

Function:  Closes water valve when in full cooling mode.

Location:  Behind R/H dash kick panel and center console in servo control unit.

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Function:  Opens center dash flap in cooling mode.

Location:  Behind R/H dash kick panel and center console in servo control unit.

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A thermistor is a device whose resistance depends on its temperature. The lower the temperature, the higher the resistance - The higher its temperature, the lower its resistance, i.e. In-car sensor, ambient sensor.

A potentiometer is a device whose resistance varies when one of its two elements is rotated either way, manually or mechanically, i.e. Temperature selector, feedback potentiometer.

Is an electrical switch which passes current at all times except when its sensing probe, attached to the evaporator, drops to 2°C (36°F).  When this occurs, the Ranco Thermostat becomes non-conductive and the circuit to the compressor clutch is disengaged closing down the refrigeration system to prevent evaporator freeze-up.

Is an electrical device which will allow current flow in one direction only.

Function:  Protects feed to compressor clutch.

Location:  Next to Ranco Thermostat on right aide of evaporator case behind dash underpanel.

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Function:  *Protects servo motor, circuit wiring and amplifier from current surge.

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Function:  To allow flow in one direction only.

Location:  D1, D2, D3 In servo motor control unit.  D5 in harness between mode control and harness plug.

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Testing:  Check that current flow in direction of arrowhead.  None in reverse direction

Function:  Measures air temperature of vehicle interior.

Electrical Diagram: 

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Location:  Behind dash center oddment tray in center of tray.

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Function:  As its name suggests, it registers ambient air temperature at R/H blower inlet.

Electrical Diagram: 

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Location:  In left-hand side of right-hand blower casing.

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Testing:  Suggest best method of testing is by substitution.  Resistance should be no greater than 3.9K ohms.

Function:  Supplies power to fans via resistors at all times when auto or low is selected.

Electrical Diagram: 

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Location:  Behind L/H console kick panel to rear of main blower motor relay.

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Testing:	If fans fail to operate in auto, low speed or low manual selection with engine water temperature above
	40°C (103°F), check for 12 volts at N/Y lead and check ground lead for good connection.  If as stated, there should be 12 volts at the N/W and Y leads.  NOTE:  There should be 12 volts at N/W white wire at all times because it is battery supply from fuse F10.

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Electrical Diagram: 

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Location:  Behind L/H console kick panel.  C.46179

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Function:  To vary the resistance in the blower motor circuit thereby changing blower speed.

Electrical Diagram: 

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Location:  Behind L/H console kick panel and dash underpanel.  RTC677

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In all but (4) above, the resistance will cause a voltage drop at the green/slate output terminal to give the various fan speeds.

Location:  Either side of the car above the dash underpanel.

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Testing:  Apply 12 volts to motor and check ground condition.  If motor fails to operate, change motor.

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Location:  On heater core inlet water pipe located above L/H floor vent outlet behind L/H console kick panel.

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Electrical Diagram: 

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Location:  On left-hand side of console control panel.  6

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Testing:  Using ohmmeter and circuit diagram, check microswitch continuity.

Electrical Diagram: 

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Location: Behind R/H console kick panel and dash underpanel.  AEU1675

Testing:  Check continuity with ohmmeter - Will pass current providing evaporator is not below 2°C (36°F).

Electrical Diagram: 

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Location:  Behind L/H console kick panel and in front of main air conditioning relay.  RTC670

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Testing:  (Same as that described in Vacuum Section)

Location:  Behind R/H console kick panel and center console.

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Depending upon the position of the temperature selector and temperature of the in-car sensor, the camshaft will rotate in either direction.

Electrical Diagram: 

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Function:  To drive camshaft in either direction upon signal from amplifier.

Function:  To limit maximum camshaft movement in full cooling mode - operated by camshaft Cam S1.

Function:  To limit maximum camshaft movement in full heating mode - operated by camshaft Cam S2.

Function:  To place air distribution flaps in position depending upon selection at mode control and temperature selector.

Operation:  Upper heating, lower heating, lower cooling - operated by camshaft Cam S6.

Function:  Closes heater water valve in full cooling mode - operated by camshaft Cam S7.

Function:  To place air distribution flaps in position depending upon selection at mode switch.

Operation:  Upper cooling flap - operated by camshaft Cam S8.

Function:  Opens center dash flap in full cooling mode - operated by camshaft Cam S9.

MODE CONTROL

DEGREE OF ROTATION

For a replacement amplifier contact sales@caulfieldjag.com.au

Electrical Diagram: 

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Location:  Behind L/H console kick panel and then behind the main air conditioning relay.  C.45402

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FULL COOLING

When full cooling is selected, the temperature selector is placed at 65.  This introduces a resistance into the circuit which lowers the current and increases the voltage.  Sensing the higher voltage, the amplifier allows the current flow through TR1, TR5 and TR3 which energizes relay RSL1 which in turn allows current flow through the red lead and return to ground through the purple lead, rotating the motor and hence the camshaft into the cooling mode.  Under high ambient conditions, the Ranco thermostat is also overridden by the Ranco override switch.

When the selected temperature is reached, the in-car sensor's resistance changes cancelling the IMBALANCE and allows the feedback potentiometer to return the camshaft to the balance position.  Camshaft travel is limited by the full cooling limit switch - Depends on Ambient influence.

FULL HEATING

When full heating is selected, the temperature selector is placed at 85.  This introduces a resistance into the circuit which raises the current and reduces the voltage.  Sensing the lower voltage, the amplifier allows current flow through TR1, TR6 and TR4 which energizes RSL2 which in turn allows current flow through the purple lead and return to ground through the red lead, rotating the motor and hence the camshaft into the heating mode.  When the selected temperature is reached, the in-car sensor's resistance changes cancelling the IMBALANCE and allows the feedback potentiometer to return the camshaft to the central position.  In full heating, fan speeds are limited to LOW and MED 1 (2nd speed) - Depends on Ambient influence.

{HANDWRITTEN NOTE To bypass amplifier hook into purple wire & red (fused) wire - to negative &/or positive }

DEFROST MODE MAXlMUM

When defrost is selected, the temperature selector is placed at 85.  This introduces a 27K resistance into the circuit which raises the current and reduces the voltage bypassing the amplifier bias circuit and causes the camshaft to rotate to the full heating mode.  The fans will operate at the highest speed.

FULL HEATING MODE - AUTO

There is no vacuum feed to center dash flap, therefore, it is closed - heater flaps are fully opened - cooler flaps closed by camshaft.  System will not operate until engine water temperature reaches 40°C (103°F).  Fans will automatically be on LO speed (1st) and switch to MED 1 (2nd) speed by camshaft.  Only the two lowest fan speeds are available in the heating mode.

Camshaft turns until stopped by full heat limit switch.

Camshaft movement depends on ambient and desired temperature set at temperature selector.  Therefore, depending on conditions, flap positions will vary to meet in-car temperature requirements.  All air is passed through evaporator to be dehumidified.

HIGH & LO FAN SELECTION

Except for maintaining the given fan speed selected, the system's operation still remains automatic.

FULL COOLING MODE - AUTO

Approximately 75% of the air after passing through the evaporator is fed to the dash outlets, the remaining 25% to the footwells.

Vacuum solenoid is de-energized placing inlet flaps in fresh air mode. Ranco thermostat is conductive and refrigeration cycle operates.  Fans are initially on LO speed (always in this mode when Auto is selected).

As camshaft revolves, it trips MED 1 (2nd speed) fan switch then MED 2 (3rd speed).

Center dash flap opens when cam operates outer vacuum switch.  Upper and lower heater flaps are closed preventing air passing over heater core.  Cooling flaps are open - All flaps being operated by camshaft through external linkage.

Water temperature bypass switch activated by camshaft - Water valve closed to prevent water circulation through heater core - Cam closes vacuum feed from inner vacuum switch.  Ranco thermostat overridden by Ranco override switch.

High speed (4th)/Recirculation switch activated by camshaft - Positive voltage via Diode #D3 energizes vacuum solenoid and allows vacuum feed to inlet flaps placing them in recirculation mode.

Camshaft trips full cooling limit switch inhibiting further camshaft travel.

As selected temperature is reached, the feedback potentiometer, via the amplifier, signals the camshaft to reverse this sequence until camshaft revolves back to central position.

HIGH & LO FAN SELECTION

In cooling mode, HIGH or LO may be selected either to maintain a high or low air velocity into the vehicle interior; however, all other functions remain automatic.

INTERMEDIATE SETTINGS

Depending on ambient temperature and temperature at the in-car sensor as compared to that selected at the temperature selector control, an infinite number of settings between full heating and full cooling are possible.  Therefore, flaps, vacuum and electronic control signals are governed by the camshaft position necessary to maintain the selected temperature.

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DEFROST

Selecting defrost at the manual control introduces a high value resistance (27K) which completely overrides the amplifier bias circuits.

The camshaft moves to the full heat position closing the upper and lower cooling flaps and opening the heater flaps.  However, the lower heating flap which normally is held open by a vacuum actuator, does not have a vacuum feed, therefore, is held closed by the return spring.  All heated air is directed to the screen outlets.  Manual operation of the dash end outlets is optional for side window defogging.

The vacuum switch on the manual control is closed preventing vacuum to the lower heating flap and screen outlet flaps (which allow screen flaps to open 90% of air flow).  There is a small bleed (10%) of hot air to the footwells.  The fans are naturally on HIGH speed (4th) and will come on immediately.

The heating system will not function until the engine water temperature reaches 40°C (103°F).

S1002 Page 64 of 88

The lower heating flap functions in all positions except defrost.  The position of the lower heating flap is modified by the overriding action of the cam and peg on the upper heating/lower cooling flap operating linkage on the right side of the evaporator case.  This linkage gives the correct air blend for all conditions.

In defrost there is no vacuum supply to the lower heating flap vacuum actuator.  Therefore, no air flows to the front or rear footwells.  In defrost mode, all air goes to screen outlets except for a slight bleed to the footwells or optional setting of the dash end outlets.

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Check relative position of flaps for FULL HEATING and FULL COOLING modes.

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Failure to do this indicates either mechanical seizure or vacuum failure.

NOTE:  When the vacuum supply is disconnected from any component, the component should return rapidly to its rest position.  Also, bear in mind that the vacuum pipes may be perished, split or pinched causing complete failure or intermittent operation.

A vacuum functional test should be performed prior to testing the Electrical/Electronic circuitry.  Use the appropriate circuit diagrams and keep in mind that shorted, poorly grounded or open circuited wires may be the actual cause of component failure.

ELECTRICAL FEED FUSE FAILURES

There are four fuses which protect the air conditioning unit:

1.	If fan motors fail to function on all speeds, check the 35 amp. supply fuse #F10 at the main fuse box.
2.	Ignition supply 35 amp. fuse #F11 controls all ignition auxiliary units, i.e. air conditioner, wipers, washers, etc.  If this fuse
	fails, disconnect feed to air conditioner and replace fuse - Operate all auxiliary items to determine whether the fault lies in the auxiliary items or the air conditioner.
3.	The third fuse is a delayed action fuse in the amplifier positive line.  If, upon replacement, the fuse still fails, the amplifier,
	thermistors, Diodes, camshaft motor and associated wiring is suspected, If no fault is apparent, disconnect camshaft motor and thermistor.  If fuse still fails, replace amplifier.
4.	The fourth fuse is a 10 amp. fuse which protects the feed to the compressor clutch.  If, on substitution, the fuse still fails,
	disonnect compressor clutch lead and try again.  If it still fails, suspect Ranco thermostat or Ranco override switch.  Test each item with an ohmmeter.

S1002 Page 74 of 88

FAN FAULTS

If fan faults exist, a voltage check must be taken at the input feed and fan supply leads.

Two additional feeds are between the 10 amp. clutch fuse and the water temperature thermostat.

FAN SWITCH FAULTS

There are five switches which directly control the fans:

COMPRESSOR CLUTCH FAULTS

CAMSHAFT MOTOR FAULTS

AMPLIFIER FAULTS

In addition to the amplifier checks performed under camshaft motor faults, the following two checks may also be performed:

CAMSHAFT MICROSWITCHES

It is recommended that if microswitch failure occurs that the complete servo unit be replaced, however, wires to switches should be checked for chafing, fraying and loose connections, etc. - Continuity checks may also he performed.

SENSING SYSTEM TESTING

Disconnect Amplifier plug from harness Socket.  Perform following test at harness socket:

HARNESS SOCKET

Pin 7 (Blue wire) to Pin 4 (White wire).  Temperature Selector should vary from 0 to 10K.

Pin 7 (Blue wire) to Pin 3 (Brown wire).

Pin 9 (Orange wire) to Pin 8 (Yellow wire).

Feedback Potentiometer = 2K

Pin 9 (Orange wire) to Pin 5 (Green wire).

Track to wiper arm of Feedback Potentiometer 0 - 2K ohms.

If Zero, servo in full heat position.  If 2K, servo in full cool.

Pin 1 (Purple wire) to Pin 2 (Red wire).

30 ohms (servo motor resistance maximum acceptable 100 ohms).

The procedure provides a check list of six tests on hand and automatic control.  The sequence must be strictly followed as each check-out is based on the satisfactory result of previous tests.  This method avoids undue repetition of tests and back referencing.

Before the fault finding sequence is started, the car engine must he run to ensure that the water is hot and that there is adequate vacuum in the system.  For subjective and cooling tests the engine should be running for the refrigeration compressor to operate.

EQUIPMENT

The chart is based on the availability of the following test equipment:

PROCEDURE

The following sequence must be followed to cover all foreseeable faults: