Post by johnwp5bcoupe on Oct 31, 2017 10:37:21 GMT
Oct 31, 2017 9:22:16 GMT @dicky said:
Morning Guys.Is there anyway that the 3AW can be bench tested for normal function?
Hi Richard I had mine fail recently so had to clean the contacts so far ok!
I got this from the E type forum and explains quite well apart from the oil pressure bit and wire colours:-
It is a sort of thermal relay. When the alternator is running the wire that goes from the alternator to the 3AW unit supplies about 8 volts AC . This warms up the wire inside and the heat then opens a bimetallic contact visible in your snap. one end of this contact is grounded and the other end goes to the ign light. So if the alternator fails the contact closes and on comes the light. The light doubles as an oil pressure warning as the oil pressure switch also connects from the bulb to ground and closes if the pressure fails. You should have a white live feed to one side of the bulb. From the other there is a brown/black to the oil pressure switch and a second brown/black to the WL terminal on the 3AW relay. The centre terminal of the 3AW goes to ground and the other marked AL connects to the AL terminal on the alternator using a brown/yellow wire. This is how the wiring diagram shows things. If you have not got one get a wiring diagram for your particular model. Hope this helps. Testing the 3AW would be by applying about 8 volts from the AL terminal and ground using either AC or DC and making sure there is no connection from WL to ground. If there is the unit is caput.
