Rear wiper problem on 04 Cooper

[steamboat]

Hi Guys,
I’m having some trouble with my rear wiper on my 04 Cooper, likely caused by the cold weather we have had lately (and my impatience to use it before the rear window had defrosted completely!). A couple of weeks ago after a frosty morning I found that when I started the rear wiper it moved back and forth maybe 10 times (non intermittent) then stopped suddenly, not in the parking position, as if the power to it had been cut off. After waiting about 5 minutes the wiper would respond again for another burst and again stop at a random position. About 8 hour later when I was back in the car again the problem seemed to have rectified itself - it was working perfectly again, intermittent when expected and stopping in the correct park position. A couple of days ago however the same problem started again, but this time it hasn’t rectified itself.
Has anyone else experienced this? Any ideas on what is causing this inconsistent behaviour? I checked the fuses and they are all fine, so I’m thinking the a relay or the wiper motor is the problem, or possibly a bad contact somewhere. I hope there is a quick DIY fix!
Thanks all

[Owen]

The rear wiper won't work if it thinks the boot is open. The boot switch inside the lock may need freeing.

[steamboat]

Thanks Owen. That doesn’t seem to be the problem here. The wiper does run for about 10 seconds before stopping and if I wait about 5 minutes it will run again for another 10 seconds… weird … also for the 10 seconds it does run it doesn’t go into ‘intermittent’ mode, it just runs flat out and then stops suddenly mid stream. (Normally when I turn the rear wiper on it will do three full sweeps and then run intermittently)

[Owen]

The only time the wiper will run for that length of time, is when you're also washing the rear glass. Which would explain the timing out too. It could be that your wiper stalk is sending a wash signal instead of just wipe.

[irlmin]

Usual problem is as Owen has said the boot lock faulty and the wiper thinking the boot is open , but we have replaced several rear wiper motors to cure some weird behaviour , have you had any water leaks into the car recently again sometimes if water leaks into the motor or a control unit it can cause weird problems as you describe ,
G

[steamboat]

Thanks guys. Haven’t noticed any water leaks, but the problem did coincide with the cold weather so perhaps something went awry with the frost. I checked the boot lock and can’t see any obvious problem there. A new control unit or motor would probably cost a bit I guess? Could a dodgy relay cause this behaviour?

[steamboat]

I decided to take a closer look at the motor to see if there was anything obvious. When I removed the tailgate trim I noticed trails of rusty coloured water running down the inside of the trim, starting from the wiper motor housing. So looks like there is a water leak alright. The window washer nozzle is blocked and it seems that the pressure build up resulted in a leak at hose connection which is right at the wiper mechanism connected to the motor. I've taken out the motor completely to dry it out to see if that makes a difference, but a new motor could be in order

[Owen]

If you have enough, put the motor in a large bowl of dry rice, enough to completely cover it. Rice is incredible at drying out moisture. However, if the water has corroded the copper windings inside the motor, you'd best get a replacement.

John Lynch, a forum member, was recently breaking a Cooper S, Ger (irlmin) has his contact details, would be a cheap replacement!

[steamboat]

Thanks for the tip Owen! I plan to reinstall the motor tomorrow (weather depending). The cogs/gears are a bit rusty looking so I plan to clean them up and replace the grease – I’m hoping that will do the trick. If not I’ll be on the hunt for a new motor.

[steamboat]

I finally got around to cleaning out the motor and found that one of the contact arms that control the current going back to the control unit as the motor turns had corroded to the point that eventually broke completely. So that's the end of that, and I'm going to have to bite the bullet and get a replacement motor
(Irlman, I've sent you a PM - if you can point me in the right direction that would be great)

Thanks again guys.

[Owen]

Well, fair play for having the determination to get to the bottom of it. I know Ger might have one in stock, and I know that if he doesnt, Lynchie (Club member with one that he's breaking for parts) - should have one anyway. You'll be up and running again in no time.