Cold climate electrical system
1 - On-off switch
(Two positions, as indicated in the figure alongside).
Pressing the switch, the built-in indicator lights up and the electric fan
will operate at speed I.
Heater fan control switch
(Three positions, as indicated in the figure alongside).
— Switch at position 1 (fan operates at speed I, due to activation of
the on-off switch).
— Switch at position 2 - fan operates at speed II
— Switch at position 3 - fan operates at speed III
Heat control potentiometer
— Rotating the control clockwise around the red sector (beyond the
initial contact), the power input to the heater unit is increased
progressively.
This type of system is essentially similar in construction to the standard system, but with the following differences:
2 - The potentiometer is coupled directly to the field coil of the heater alternator (this version has no electronic control
unit).
3 - The system incorporates two thermal overload cutouts set respectively at 70°C and 100°C. The first of these
(normally open) serves to prevent temperature peaks in the heater unit when switched off immediately after a
prolonged period of operation; the second (normally closed) functions as the safety device providing thermal overload
protection for the overall system.
NB: If the air flow temperature rises to 70 °C with the fan operating at speed I or speed II, the first thermal overload
device will trip and switch in fan speed III; this will take place even with the ignition key in the OFF position.
A first relay located above the fuse box is connected to the fan control. When the fan control is set to speed I or speed
II, current flows to the fan speed resistor, passing through terminals 87B and 30 of the relay. With speed III selected,
conversely, the relay passes current (12 V) by way of terminals 87 e 30, direct to the fan motor, by-passing the speed
control resistor.
A second relay, also located above the fuse box, is connected to the alternator voltage regulator and will operate
whenever the second thermal overload cutout trips on sensing an air flow temperature of 100°C. The contacts are
wired to cut off the flow of current from the regulator to the field coil.
4 - Whenever the potentiometer is rotated beyond the initial contact, the fan automatically switches in at speed I.
systems
air conditioning
On/off switch
Heater fan control
Heat control potentiometer
86
8
357
www.maskinisten.net
www.classicmachinery.net
To Next Page
Loading...
