2 - With the ignition key in the ON position (engine at standstill) and the heater and fan control switch at position 1, apply
the “+” prod of the voltmeter to terminal 5 (yellow/blue - 1) of the 6-way potentiometer and the “-” prod to terminal 1 (green
lead - 1), as indicated in Fig 4. The reading should be 12 V.
Next, transfer the “-” prod from terminal 1 of the potentiometer to terminal 4 (black/white lead). In the event that the
reading given is other than 12 V, detach the leads from the potentiometer and verify that current passes between
terminals 4 and 5. If not, replace the potentiometer.
3 - With the ignition key in the ON position (engine at standstill), the heater and fan control switch at position 1 and the
potentiometer activated, apply the “+” prod of the voltmeter to terminal 3 (grey - 1) and the “-” prod to terminal 1 (green
lead - 1), as indicated in Fig. 4. The reading should be 12 V. If not, check the alternator relay located at the rear of the
fuse box. Then proceed as in step 7.
4 - With the ignition key in the ON position (engine at standstill), the heater and fan control switch at position 1 and the
potentiometer activated, apply the “+” prod of the voltmeter to terminal 2 (orange - 1) and the “-” prod to terminal 1 (green
lead - 1), as indicated in Fig. 4. The reading should be 12 V.
Turning the potentiometer steadily clockwise, check that the voltmeter gives the following readings:
- Potentiometer at minimum setting = 1 V
- Potentiometer rotated half way = 6 V
- Potentiometer at maximum setting = 12 V
If the voltmeter fails to give a reading, inspect the wiring connections at the potentiometer and check for any traces
of oxidation. Clean if necessary and reinstate.
If the values indicated by the meter are low, check that the heater alternator drive belt is properly tensioned.
5 - With the ignition key in the ON position (engine running at 1000 rev/min), the heater and fan control switch at posi-
tion 1 and the potentiometer activated, test for the correct voltage input at the heater resistance element while rotating
the potentiometer:
- Potentiometer at minimum setting = 1 V
- Potentiometer rotated half way = 10 V
- Potentiometer at maximum setting = 26 V
If the voltmeter gives no reading, check the wiring connections, which must be sound, clean, and free from any
traces of oxidation.
If the readings are low, check that the heater alternator drive belt is properly tensioned. Recheck the voltage input
at the heater element, this time with the engine running at 2500 rev/min, while rotating the potentiometer. The volt-
meter should give approximately the following readings:
- Potentiometer at minimum setting = 1 V
- Potentiometer rotated half way = 14 V
- Potentiometer at maximum setting = 38 V
6 - If there is no supply of current from the alternator, stop the engine and disconnect the black lead running from
the alternator to the heating system. Verify the continuity of the resistance with a tester, which should give a read-
ing of 1 ohm or thereabouts; if the value registers high or infinite, then one of the elements is defective.
systems
air conditioning
86
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