Massey Ferguson 390 , 3 pin plug not work (fuse hasn’t blown)

[Lang farmer]

When I plug the control box into the 3 pin socket nothing happens , I have checked the fuse and it has not blown

 

[topcat2006]

What happens if you put a voltmeter on the pins - do you get voltage?

How did you test the fuse? Visually or with a continuity tester? I have known fuses to visually look ok but not make a circuit.

If the fuse is and no voltage at the socket then wiring between the fuse and socket needs looking at - back of plug would be good place to start.

Does the control box work? Has it been tested in another tractor? (Or have you another control box you can test in the 390?

 

[Lang farmer]

When I use a voltmeter there was no reading , I then went to check the fuses so I checked every single fuse on the tractor visually and none were blown , I then checked the control box with another tractor and it worked fine , could there be a inline fuse somewhere?

 

[topcat2006]

There could well be - especially if it was fitted after market. Is there anything in with the battery?

I would think that the fuse for the socket will be about 15-20 A, can't remember what the sockets are rated too.

 

[Exfarmer]

Is it wired correctly? They should be wired one earth, one wire live permanent one live through the ignition.
If plug and socket are not match wired they will not work, common issue

 

[Lang farmer]

They have worked for the past ten years but today the screen on the box wouldn’t work, when I tried it on another tractor it worked fine , when i tested it with a voltmeter it read nothing

 

[Dry Rot]

One of the best investments for electrical repairs is a tin of switch cleaner. Not WD40, but the stuff that dissolves the corrosion. (I'd give a squirt to the connectors before checking wiring). Then try waggling wires to see if power returns.

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[Lang farmer]

I have resolved the problem by rebuilding the 3 pin socket