Rear Wiper Fault?

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miss2b
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I have a 463 SWB G Wagen and got a probelm with the rear washer working.

I understand that the washers operate using a bi-directional pump.   That is, that polarity is reversed depending on whether the front or rear washer is used/needed.   The problem that I have is.... whilst the pump operates in the forward direction to operate the front windscreen washers, when I operate them in reverse, instead of the voltage reversing I loose all power to it.    

Presumably there is some clever way in the washer stalk arrangement to enable the reverse in voltage.  Does anyone know or explain how this is  achieved or alternatively, does anyone have a wiring diagram for my gee?

Many Thanks in advance.

Missb

gav.helme
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Re: Rear Wiper Fault?

Hi

I understand the pump part, but i thought the rear washers operated from a rocker switch on the dash?

Not 100% mind, so will stand corrected....

Spider1V
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Re: Rear Wiper Fault?

 As Gav has said, there is usuallly a rocker switch on the dash (in fact two) one for continuious and intermittenet and one for the actual wash wipe..... Can you take a photo of the dash above the gear stick up to the vents and post?

Spider1V

miss2b
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Re: Rear Wiper Fault?

 Yes..... I have the rocker switches.   The one switch operates and shows two speeds 1 and two.  And I have the washer switch for the rear.  But it just moves the blade but no water comes out with it, hence why we checked the pump etc

gav.helme
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Re: Rear Wiper Fault?

Sounds like you need to do some simple multi meter tests, if you have not done so already?

This is from my basic knowledge, so i will stand corrected if and when somebody else replies.

Pop the rocker switch out, see if you have a 12v feed to the switch in the off position, with the ignition on (should have if the wiper works)

See if when the wiper is operated you still get 12v out to the wiper terminal (should be OK)

See if when the washer is operated you still get 12v out to the washer pump terminal

All these are at the switch end. If you have no 12v out to the pump then suspect the switch is faulty (you could clean the contacts etc)

If all OK then do the same at the pump end, check for 12v when you operate the washer switch.

If you have a 12v supply to the pump and it does not operate then you either have an earth fault or a faulty pump.

Hope this helps

Gav

Pistonhead
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Re: Rear Wiper Fault?

Hello miss2b,

When you operate the rocker switch, do you hear the whirring of a motor? If not, obviously the motor is not working. If, noise is heard, but no water squirting out from the rear jet; it is common for the the pipe, feeding the rear wash jet to become detached. Or, the jet is simply blocked up. Use a thin pin or needle to unblock the jet hole.

A quick way to test out the motor; taking two short pieces of electrical wire, of about two inches long, attach a male-ended spade connector to one end and at the other end, attach a female-ended spade connector to each of the wires. Pull out the socket connecting from the pump. Attach the bridging wires in between the pump and socket.

Operate the wash jet by the indicator stalk, this will operate the windscreen wash jet. Next step, pull out the connectors from the socket side and re-insert them into the socket, but this time around swap the terminals in the socket, operate the stalk again. This should operate the rear wash jet, if not, this will confirm a blockage issue or indicate pipe detachment.

To access the panel covering the wash jet, open the tail gate door, pull away the left side (viewing the vehicle from rear, forwards) trim which runs from the top of the door pillar, to the bottom. The rear-left interior panel will come loose attached by speaker wires. Disconnect the speaker wires and the wash jet and pipe will be exposed. If the pipe is detached, reconnect this. Usually, there is a one way valve fitted in line. These can cause blockages which you could either remove or replace. Removing the valve simply means, when the wash jet switch is operated, it takes a little longer for the water to squirt out.

One of the rear wiper switches selects for either an intermittent wipe or continuous wipe. The other switch operates the rear wash. I am not quite sure, but I do think, you may need to hold the switch down as the jet is either instantaneous or it squirts only when the wiper blade comes to the beginning of its sweep cycle.

Cheers,

fixwin38
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Re: Rear Wiper Fault?

Hi
90% chance that the pump ( located left /drivers side of the engine bay close to the radiator) has become clogged with screen cleaner gel along witht the non return valve located behind the trim panel on the washer head ( triangular plastic housing for the washer jet) inside of the back door only accessible when you remove the panel..you might try using a pin to clear the jet head as this can block as well*** the pump can be dismantled and the crud cleaned out which will save you £70 if it works................. and most times it does
make sure your remove the correct pump as there is more than one located in the same area

miss2b
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Re: Rear Wiper Fault?

;Thanks for the replies everyone

The pump, pipes etc are all good. If voltage is applied it pumps forward, when reversed it pumps back.

It's the voltage for reverse or pumping to the rear which is missing. There is zero voltage when I switch the rear wash to on. I need to work out how that is applied through the switch. Presumably when the front washer is not working and power is called to the rear somehow that voltage is reversed. That's the bit I need to find, how that reversal happens. A wiring diagram is ideal if anyone has one to save pulling it all apart wire by wire.

Thanks for all the help.

Roly
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Re: Rear Wiper Fault?

Circuit diagram for rear wiper.
OK Iam not able to upload any files to the board. Send me you email address by PM and I'll send it to you.
The rear switch is a toggle which reverses the polarity. Does the bl/red wire ground when you turn the rear wiper on?
Fault is likely to involve removing the centre console to access the switch.
R

panzer
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Re: Rear Wiper Fault?

Assuming the windscreen wash pump set up is the same for 460 and 463. That is  3 x pumps front windscreen rear windscreen and headlights - ignore this if different!

My rear has pump has failed 3 times in 9 years. First time pump (dedicated for the rear washer) was blocked  - so removed, dismantled,cleaned and replaced.

Second time it was the dash rocker switch which needed a dose of switch cleaner to get it working.

Third time the pump packed up and I bought a new one. After market pumps are cheap but MB have them in stock and they fit first time.

Finding the faults took me ages.The advise gived by other contributors above should save a lot of time tracking the fault.