Alternator

[hilux]

Testing the alternator on the tractor got 14.2v on 2 of the leads and 7.65 in the lead shown with the quick connector, is this correct?

 

[njneer]

Sounds about right, best way to test an alternator is to switch on all your high consumables such as lights and heaters etc and make sure it still produces more than 12v if it makes any less then it will draw the difference from the battery and eventually drain it.
The small terminal depending on the symbol , “W” usually provides a pulsed speed voltage reference to generate the RPM displayed on the dash, B+ Is usually the ignition supply to provide the ignition light on the dash and excite the alternator to start charging .

 

[Pheasant Surprise]

As above. Good advice.

Anything auto electrical, you really want to be testing “loaded” that is drawing some decent current. Use a test lamp for example.

It’s too easy to use a digital multimeter (DMM), see what appears to be the correct voltage and move on to the next thing.

The only exception are ECUs and some sensors, where precise voltage measurement requires a DMM and you don’t want to draw too much current lest you risk nuking the input or output stage protection (or worse).