Windscreen washer pump
The rear window washer has stopped working on my 463 G300. The front washer is fine.
It would help if I understood how the pump works as there are two outlets from the one pump - I assume that one outlet goes to the front windscreen and the other outlet goes to the rear.
But the pump only has two electrical connectors on the top so what causes the water to go to the rear rather than the front?
Is it that the pump works in reverse to feed the rear? Or is there a valve somewhere in the water circuits that stops water going to front or rear depending on which switch is operated?
Anyone know the answer?
Oh, thats a good one. I have simlar with a 460, and assume the pump might be the same. I will dig around.
460 has seperate pumps for front and rear
The larger of the two pumps does the headlight washers, as far as I know the smaller pump feeds the front and back windows, can you hear any pump running when you press the switch for the rear window?
The switch when pressed gives power to the pump?
Be that front or rear
Might struggle if both are pressed together
But you might struggle too!!
Still think it's the switch or wiring to it
Thanks Gav.
It would help if I knew what was supposed to be happening. There are only two electrical connectors on the one pump so what makes the water go to the front or the rear?
Does the pump operate in two directions - so positive and negative elec feeds depend on which switch is operated)?
The pump is plastic and doesn't appear to be earthed (other than via one of the two connectors on the top)
Will have another go with the multimeter when the weather gets a bit better.
I think that's the way it works, you could just swap the wires around see if rear washer works when you press front stalk?or use a multimeter and a assistant?
hello,
I have just replaced my washer pump for the reason of front screen not working.
plus some fool at a garage broke the pump and lost the internal impeller !
there are two pumps on the W463 one for head lamps
one for the font and rear washer - firstly check the rear wash pin hole is not blocked - use a pin to clear the spray hole ! (we did that last !)
then test the motor is running with power from another supply,these old car terminals oxidise and lose connectivity
clean up terminals or fit new female connectors and it should work (test before refitting)
note; be careful when removing as these parts can become brittle
If the motor is not working - you can fit another from a different vehicle as they are all the same size
When you find an orginal one,you can swap back
Make sure that the problem is not a leaking water pipe. They have been known to leak near the hinge side of the rear door up at the top. If that happens you will get a bad case of "tin worm" just inside the lower near side door shut. I have that problem, It is not a pretty sight.
I hope you find it is only electrical.
Regards,
Alex.
Look what I've invested in. I will report back once I've found time to fit.
So, I now have fully functioning high pressure headlamp washer. 
Unfortunately the rear windscreen washer still not working. More investigation needed.
Now have a new rear windscreen washer switch on its way to me.
I'm sure I've done it before but can't remember how. Does anyone know how to get to the switches on the centre panel on an early (1991) 463 G300?
It's possible that I'm remembering from when I had to do it on my previous car (MB 300TE). I think on that occassion it was quite compliacted and involved taking off the steering wheel so if someone knows for sure or can point me in the right direction that would be great.
You have to remove the steering wheel to remove the long wooden strip, ( this is easy to break) some screws behind that, can't remember if screws at the bottom, go easy on the switch panel, as not much free/ extra wire onthe diff lock illumination, double check everything works before reassembly!
In the hope that it might help someone else (as several have mentioned that rear window washer switch does weird things).
As a reminder, pushing the rear windscreen washer switch used to work the rear washer AND the rear wiper AND the front wipers (no, that's not supposed to happen).
Eventually, after several years of just accepting the status quo, the rear washer stopped working.
I've now fitted a new MB rear washer/wiper switch and everything works as it should. The rear washer/wiper switch ONLY operates the rear washer and rear wiper and has no effect on the front wipers.
The only conclusion I can come up with is that the front wipers and the washer pump are wired through the rear washer/wiper switch and it's this that controls the positive & negative feed to the washer pump and therefore controls whether the washer fluid goes to the front or rear windscreen. There are a lot (8) of connectors on the rear washer/wiper switch so they must be there for something.
Remember
This is only applicable to a 463
Front / Rear washer on same pump and headlamps on another if it has that option
460's have 3 pumps, one for each function
My rear wiper switch also occasionally causes the front wipers to operate, how much was the switch? Also 463
I got it from Gav with some other bits.
Gav??
My 460 wiper doesn't complete a full wipe and return to home. I have to more or less stop it manually with the switch. Does that sound like switch, or wiper motor?
Bear in mind that:
Mine is a 463
I'm not an electrician
I'm a potterer, not a mechanic
But having taken my old switch apart to see how easy it would be to replace the internal light bulb, I can't see how the switch would cause your problem. It's either ON or OFF.
My GUESS would be either the motor or how about the relay. I see you have two 460s - why not try swapping the wiper relays over and see if that solves the problem one. If so you just need a relay. If not then some adjustment to the wiper motor or possibly the linkages.
Hopefully someone who knows what they're talking about will be along shortly.
I'm a potterer, not a mechanic
Thanks all the same. Experience is what counts and feeding it back.
I think the problem I have is likely the motor. I imagine the switch triggers the start of the wipe, and the motor should have power to complete a cycle. If I have to press the switch to make it continue, I am presumably overcoming that lack of power. Like you I will have a potter. Being the rear, I tend to ignore it and then remember when it is raining which has been a lot lately.
I got it from Gav with some other bits.
Gav??
Think about £70 that was just a new one I had at home I supplied you cheap
You lucky boy ;0)
On all my G's the rear wiper doesn't like to park and will struggle to do so 9/10
if you operate the switch on and straight off this happens
If you leave it on it doesn't...
If you switch it on and watch and switch off when near its park position it's ok
I am only a potterer also but that would lead me to believe a bad earth connection?
Never bothered me and everything else works ok so have just lived with it
"I am only a potterer also"
Oh, how I laughed.
Hello, I think you may find that if the pump is working you may just need to clean out the jets on the rear
You can check by removing the pipe from the pump to check working - water is driven by an impellor on the top inside of pump ,I am assuming when you press the swithch it makes the motor reverse sending water to the rear screen. (thats how it works?)
I have just changed my washer motor front/rear ,all was electrically fine when new one fitted but no water ! cleaned out the jets with a pin 'hey pressto !' all good now !
maybe worth cleaning the electrical spade connections on the pump electrical supply (oxidisation occurs)
I used an old motor from a BMW (I think) as the replacement - works great
Regards
Tyrekicker (Mike)
Thanks Mike,
I did clean out the jet but in the end (process of elimination) it turned out to be the rear wiper/washer switch. That has a lot of connectors on the back and, although I'm certainly no electrician, I can only think that the power from the front wiper/washer also passes through this switch and changes polarity. It's the only way I can think that the one pump feeds both the front and rear windscreens (although not at the same time). It also kind of explains why when I pushed the rear washer switch previously it also activated the front windscreen wiper for a few swipes.
Anyway, all working perfectly now and the G benefits from 2 new washer pumps (windscreens and headlamps) and a rear washer/wiper switch - all for the cost of what I'd probably have had to pay an auto electrician for his labour but a certain amount of satisfaction from having managed to do the job myself.
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I hear the pump running when the front washer operating but no pump running when I push the rear windsreen washer switch.
What I can't work out is how does the one pump operate both front and rear given that there are only two electrical connectors?