wipers won't turn off MG ZT

[polly04]

Hello
I own a 52reg ZT 190 and I cannot switch the windscreen wipers off. As soon as I turn the ignition once, off they go. When the car is stood they go about normal speed , but when I set off they go even faster. There are two wiper relays which I tested and they both switch ok. There are four cables to the wiper motor one negative, two positives and one smaller positive which comes via the body control unit. If I test the voltage at the motor all three cables show 12v to negative, however if I unplug the wiring connector to the motor and test, only the smaller cable shows 12v. I don’t understand if this correct or not, it gives the impression that motor its self is applying the voltage to the two other cables.
Any help would be appreciated It’s driving me mad and it’s bloody embarrassing when the sun’s out

 

[Spark123]

When you test with the plug out, are the other two wires energized only when the wiper switch is operated at normal/full speed? If so I'd suspect it is the part of the mechanism attached to the motor/mechanism which sends the wiper back to the park position is goosed, although I'm only speaking generally as I am not 100% sure on the setup on your particular car.

 

[polly04]

Hello spark 123
The wipers go all the time even when the stalk switch is off.

 

[jonnyfishing]

I agree with Spark123, and I am also unfamiliar with this model. Have you checked the wiper switch ? if it's faulty it could be energising the motor every time you switch on.

 

[polly04]

Hi
No I haven’t checked the switch yet, it looks like a special tool is required to get the bottom off the steering canopy. I don’t think it is the stalk switch because if it was knackered I would assume it would make the wipers go at one speed, but they speed up when driving.

 

[jonnyfishing]

If you acquire the Haynes Manual (book No.4292) and using the wiring diagram for the wipers you should be able to identify which wire energises the park, cut it (you can always rejoin it) and see if that cures it, if so, it proves where the fault is.

 

[Spark123]

I don't think you need to dismantle the dash just yet, I'd be tempted to just the voltage checks at the 4 way plug at the motor. I was under the impression there is an ignition 12v supply all the time to energize the wiper park circuit? Other than this I'd expect to see 12v at one other with the wiper switch on normal setting and 12v on the other with the wiper on full. I may be completely wrong though!
Post back with the results.

 

[polly04]

Update
Replaced the stalk switch today, everything now ok.
Thanks for replies