Windscreen wipers blowing fuses

[Rubce]

Hi All

Our GT6 has an irritating habit of blowing a fuse (30A) when I switch off the wipers. It did it whilst I was driving home in the dark on Wednesday night which was irritating given that that fuse also controls the indicators and brake lights!

Yesterday as I was getting ready to come home from the Workshop it was raining a bit so I popped on the wipers and then switched them off again. Pop goes the fuse! Four fuses later and I gave up and disconnected the wiper motor so I could drive home with indicators and brake lights.

Any suggestions as to what may be causing it?

Regards

Bruce

[esxefi]

tricky one.

I would start with isolating the motor and looking for an earth leakage,now the thing is you need to work out what resistance each wire should have as it is a 2 speed motor and they will have different values.
but on the plus side if it only blew a fuse when you turned it off it could be the isolator switch in the wheel housing that is faulty.
I need to look at a wiring diagram to be more precise but I would start there.

[Hogie]

Hi Bruce,
              the wipers run OK when working (at both speeds or is it one speed)
They turn on OK.
It is the turning off that causes the problem.

Try operating the wipers without the switch - disconnect the wires and link direct to the battery through a fuse and see if it pops.

The two speed switch is a little bit complicated inside and could fail (sort of) - not sure about the single speed switch.

Because the wiper motor has windings it will produce a back EMF when switched off. This shouldn't be big enough to affect a 30A fuse, but.....
If desperate you could fit a diode from the fuse to the motor - but htis doen't sort out the fault.

Roger

[bodders1]

Check the wiper switch.  It should normally provide a +12v supply when the wipers are on, and then break the supply when you turn the wipers off.  It sounds like, in addition to breaking the supply, it is somehow also connecting the wiper motor supply to 0v.  

Remeber that the self-park mechanism has a separate +12v feed from the ignition switch that by-passes the wiper switch.

What I think is happening here is that when you turn the wipers off, the self-park mechanism is continuing to provide +12v to the moter and, inherently, also to the wire going back up to the wiper-switch.  If there is a short in the switch when it is in the "off" position, it would cause a very high current via the self-park mechanism and blow the fuse.

Presumably, you have a two-speed wiper motor.
Disconnect the plug at the wiper motor and identify the 3 wires that come in to that connector from the ignition switch (blue/light green, red/light green, & brown/light green).  With the ignition off and the wiper switch in the off position, use a continuity tester to check for any connectivity between each of these wires and battery 0v - there should not be any.  If any of these wires show that they are connected to earth, then the fault is most likely to be in the wiper switch itself.

Hope this helps

[Rubce]

Thanks guys for all your valued suggestions. Hopefully I will some spare time on Sunday to investigate further.

The self park switch does not work. I wonder if that is contributing to the problem?

Mind you the self park doesn't work on our Stag either and that doesn't blow it's fuse. I have become very adept at stopping the wipers in the correct place

Regards

Bruce

[Hogie]

If the wiper motor is similar to the TR motors then the +12v feed is fixed (on) and it is the earth that is broken by the switch.
The self park simply continues the earth - through an internal wiper strip.

Roger

[RobPearce]

Quoted from Hogie

If the wiper motor is similar to the TR motors

It depends, mostly, on whether it's a single-speed or dual-speed. The former were ground-side-switched with the limit switch internal, while the latter are positive-switched through a white plastic connector and limit switch block.