Section O (26/12/08 )


O.1     The system
O.2     Removal of the heater unit
O.3     Controls 
O.4     Adjustments and maintenance


Sabra Handbook Plate 14




The Heater Box is centrally mounted behind the engine bulkhead, between the dashboard and front tunnel cover. The box is secured by bolts to two side brackets. Mounted inside the box is a smal fin-and-tube water radiator which is connected across the engine cooling system by two flexible rubber hoses.

The top flow hose circulates water from the front cylinder head connection through a water valve to the heater radiator. The second hose returns the water from the radiator to the cylinder head when the engine thermostat valve is open.   

In the Right Hand Drive car the water valve is fitted directly into the side of the cylinder head using an adaptor union and fibre washer.   

In the Left Hand Drive car the water valve is independently mounted to the engine front bulkhead on brackets and secured by two screws. This variation in position results in the water valve hose being sliced in two. The longest length is used to link the valve to the elbow adaptor which is fitted with a fibre washer to the side of the cylinder head.  

The water valve is cable operated and trunnions secure the cable to both valve and heater master control. Jubilee clips secure the hoses, at the heater box and cylinder head connections. In addition the hoses are clamped to the air inlet trunk by two straps. The fresh air inlet is in the form of a large flexible trunk which supplies air to the heater box.

A metal support tube is held to the chassis with a strap. and the flexible trunk is retained at both ends with two clamps.

A flap mounted inside the heater box trunk connector controls the flow of air to the car interior. A single trunnion and strap secures the operating cable between the flap and master ventilator control.

Mounted in the base of the heater a second flap, again cable operated, directs the air flow. With the flap open, the air, hot or cold, is directed to the car interior. When the flap is closed, the air passes through hoses from the rear of the heater to the demisting/defrosting vents.

The two hoses which connect the heater to the vents are retained with clips and two adaptors are used to connect the hoses to the demisting/defrosting vents.

In the Right Hand Drive car the vents are mounted with their nozzles pointing in opposite directions, but in the Left Hand Drive the vents are 'handed' and both point outwards. The volume of air entering the system can be boosted by throwing the 'Heater Fan' switch. The switch operates the electric motor and fan mounted inside the heater box.





1.        Remove the two demisting/defrosting hoses from the rear of the heater unit by releasing clips.

2.        Remove the two water hoses from the rear of the heater by removing clips.

3.        Detach the air inlet trunk from the heater by removing clip.

4.        Unscrew trunnion and strap located on the air inlet trunk connecting tube and remove 'Push-Pull' cable.

5.        Remove heater fan and motor wires from 'Heater Fan' switch.

6.        Unscrew bolts from heater box side mounting brackets and lift out heater box. The replacement of the heater unit is the reverse procedure as above



1.    Admission of Air
Air is admitted to the car interior through an aperture beneath the heater box controlled by a flap which is linked to the dashboard 'Push-Open Air' knob. Air is diverted to the demisting/defrosting vents above the    dashboard when this knob is pulled out.

2.    For Cold Air to Car Interior. With the'Push-Open Air' knob IN :

a.    Rotate master dash knob to 'Off'.

b.    Set secondary dash knob for volume of air required, between 'Closed' and 'Open'.

c.    To boost the volume of incoming air, throw the dashboard 'Heater Fan' switch down. This will start the fan motor -switch off to receive air under ram only.

3.    For heated Air to Car Interior. With the 'Push-Open Air' knob IN :

a.    Set the mister dash knob to desired position by turning from the 'Off' position through 'Warm' to 'Hot, setting is infinitely variable.

b.    Set the volume of air required by infinite variation between 'Closed' and 'Open'.

c.    To boost the volume of incoming air, throw the 'Heater Fan' switch down.

4.    For Cold or Heated Air to Screen. Adjust as for 2 or 3 above, but with the dashboard 'Push-Open Air' knob pulled OUT.




 The heater fan motor is wired to the dashboard ‘Heater Fan’ switch.  If a fault develops, the motor and fan can be withdrawn rearwards from the heater box, by removal of its three flange bolts, for necessary attention (See wiring diagram in Electrical System).



All other heater controls are mechanically operated and are linked by flexible wires to the two rotary knobs and the push-pull knob. The cables are screw clamp retained and pre-set at the knob spindles and heater box levers.

The master dash knob operates a rotary water valve which is fitted in the top flow water hose.

Knob spindles and inner cable ends can be lightly greased from time to time, to ensure ease of operation.


Common Technics