Rear Wash wipe Saga on a W639 Vito how difficult can it be ?

[tjamesbo]

I decided it was time to get the rear wash on the Vito working The wiper works but there was no water so anxious to avoid a scenario where it has come off the wiper inside the tailgate and is pumping into the tailgate over the lock and wiper electrics I decided it needed sorting Initial Diagnosis revealed the Pump for the rear wash pump not to be working as there " appeared " to be voltage there so I sourced a new pump
Pump arrived connected it up bingo it spins so inserted it and then tried with the pipe disconnected at entry to the rear wiper motor housing inside the tailgate Now the pump doesnt spin at all so its all off again tried it with a independant 12v supply from a spare battery and it works I now think right I'll make sure I remember the polarity orientation of the supply and suprisingly the pump works whichever way you connect it eh ? hows that ? and I mean it pumps out water whichever polarity you choose however the pressure was substantially greater on one than on the other so the strongest was noted for reference on refitting
When Refitted I could then get a lot of water at pressure out of the pipe on the tailgate just before it enters the wiper motor so I then connected it up to the wiper motor but disconnected the spray nozzle block on the wiper arm so as to eliminate that if still no water . Now no water comes out so it appears that there is either a blockage inside the wiper motor assembly where the water piper runs through it or in the tube exiting from the wiper motor to the wiper spray nozzle so it looks like I'm going to have to remove the wiper motor now to check the tube and the route thru the motor ( I'm wondering does the wiper have to move for the water to come thru ???? as I'm still using my independant 12V supply therefore the wiper is not moving )
My second problem is that the pump only appears to work when I use the independant 12V supply when I voltmeter the Contacts on the connector for the pump i get a 12V ish spike which almost immediately dies to nothing so cant be a fuse problem is there a relay or something that times the pulse on the pump for the rear wash other than this why have i not got a constant 12V at the connector contacts when the rear wash wipe switch is pressed I Thought fixing this would be straightforward and not turn into the saga it appears to have become ! must be one of the simplest systems on the van surely not that hard to fix All i need is constant 12V and a clear path

 

[tjamesbo]

Blockage is clear now wiper motor off and then the wiper motor cover off and the pipe that runs through it was blocked so good flow now and its coming through the nozzles and lop and behold the motor works on the switch so at long last a result
All I have to do now is put the rear tailgate trim back on and get some replacement trim fasteners ( the green pop jobbies )
Boyd

 

[m80]

New rear wiper motors, new and unblocked are approx £26.
I sourced an A class motor for the washer that worked out cheaper than a 639 and does the same job.

More for others with these problems as your sorted.
MERCEDES BENZ INTERIOR DOOR/CARD/PANEL/TAILGATE TRIM CLIPS 10PCS | eBay

Just checked, the wash and wipe doesn't work with the tailgate open,
I don't know if that applies here.

 

[BTB 500]

I decided it was time to get the rear wash on the Vito working The wiper works but there was no water so anxious to avoid a scenario where it has come off the wiper inside the tailgate and is pumping into the tailgate over the lock and wiper electrics

The pipework joint that came apart on mine was on the body side, behind the lights. Water pouring out under the van. The wiper motor also died - judging by the number of W639s I see with the rear wiper stuck at an odd angle this is a fairly common fault! Good work on sorting yours out.

 

[m80]

I've just replaced the brake light switch on mine.
I opened the tailgate so I could see the 3rd brake light while operating, strange but that gets disabled as well.

A heads up, the switch supposedly for mine, is keyed differently for the plug.
Rather than the hassle of a return I cut out an extra keyway, it worked.
I thought they would all be the same.

 

[tjamesbo]

Just checked, the wash and wipe doesn't work with the tailgate open,
I don't know if that applies here.

Thanks ! M80 That would explain why I couldnt get the pump to work after trying it before inserting it I then opened the tailgate to look for water out of the pipe....................... and thereby disabled it . It caused me some swearing and was going to return the new pump motor £20 all in off E-bay, but decided to test it first by direct connection to a battery , so I suspect i just had the internal blockage and the original pump was fine I automatically assumed it was dead and the disabling would explain the brief 12v spike i got on the voltmeter enough to register but not enough to start / drive the pump
Ah well that is interesting we live and learn one of my favourite business sayings was " the one thing we can assume is that we cant assume anything " generally stood me in good stead .

 

[BTB 500]

suprisingly the pump works whichever way you connect it eh ? hows that ? and I mean it pumps out water whichever polarity you choose however the pressure was substantially greater on one than on the other so the strongest was noted for reference on refitting

Forgot to comment on this yesterday! It will be a simple centrifugal pump - optimised to run in a particular direction (also the brushed motor that drives it), but they do produce some pressure when spun the wrong way.