My Mk2 that I have been refurbishing has wiper’s that won’t switch on - they were working fine a couple of weeks ago but now nothing?
the red and green wire on the switch has power in the off position but in slow or fast position no power anywhere- not even red and green wire?
Any suggestions?
can the switch be dismantled?
Cheers from Oz 🇦🇺

 

Woah, stop and don't attack the switch. It does not supply power to the wiper motor.
The wiper motor is fed power whenever the ignition is on. This is via the green wire.
Check for volts coming in on this green wire.
The switch provides a variation of different earths for slow, fast and park.
I have rebuilt over a dozen of these wiper motors and have never run across a faulty wiper switch.

 

Thanks Bill - so with the ignition on there is full power on each wire going to the wiper motor- does this seem correct?

Cheers Linton

 

There is a big bunch of wiring at the Windscreen wiper motor. It attaches to the ignition green switched wire. This car has been converted to under dash wipers so shows wiring harness well. The return lines go to the switch for the functions Bill explains.

 

Linton
You are basically correct.
The GREEN wire feeds the 12volts to the wiper motor when the ignition is on.
That feeds power to all of the wiper circuits and consequently you can see volts coming out on all of the other leads.
The system then works by the wiper switch selecting and providing an earth on the appropriate lead.
This system is called earth switching.
To be honest this electrical system is weird, but it does work.

 

So does that mean one of the wires on the switch has to be a good earth?

 

All the wires on the switch have to earth properly to provide the switched function.

 

Normally the black wire is the earth as the solid green wire is power. If you look on the back of the switch there is a black wire going back into the wiring loom that will be the earth. If you have a break in this wire or it does not connect to a good earth then the wipers will have power via the green wire but no earth. You could test this by first putting a multimeter on any of the coloured wires on the back of the switch with the ignition on to see if you have power. No power and you will have to go to the other end where the wires come out of the wiper motor and do continuity checks between there and the switch. I think you said you had power on the green wire at the motor. If you have power at the switch disconnect the earth and run a fresh earth to a point on the body. It is a case of chasing smoke but if done methodically you should find the problem.
This is the wiring diagram of the wiper motor and switch from the S Type I hope it is the same as the Mk2.
You can see on the diagram that the wires change colour from the wiper motor to the switch. Where they change colour I would assume there are joins in the wires or push in connectors. (Male bullet plugs going into black plastic joiners). These push in connectors can corrode and might need finding, stripping out and cleaning.

 

I replaced every Male & Female bullet plug on my car. Yes that cost me a new set of harnesses & lots of single, double & 5 way female connectors. The electrics are trouble free touch wood. One Ammeter did fail on initial start up but I had plenty of spares & that was quickly rectified ~ no pun intended.

Lucas even made a 10 way female connector for Jaguar.

 

Linton
The black wire on the switch is the earth.
Check that it is properly connected.
By the way always check that the scuttle air vent is CLOSED before opening up the centre switch panel.
Otherwise, the dash handle controlling this vent will foul on the switch escution panel and break it!
Been there - done that.

 

Great advice from a wise & experienced man.