rear wiper U/S

Chat about your MKV (6N2) Polo
Polofrank
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Drives: Polo estate TDI 2001
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rear wiper U/S

Post by Polofrank »

Ok guys, here to see if any of you have the answer to my problem with non-op rear wiper.

Car is a 2001 Polo Estate 1.9TDI and as such is in some aspects very different ( apart from the obvious shape ) to a Polo Hatchback of this vintage.

I have already come unstuck a few times with getting 2nd hand parts only to find they are incompatible with my Estate version of the Polo .

Anyway, back to the wiper. Things checked so far are wiring in the top of the door frame.... had to repair 3 wires on the LHS and one wire on the RHS. This fixed the hatch open continuous warning light but not the wiper.

Connecting a battery direct to the motor has the wiper sweeping to and fro just fine.

Fuses checked in the fuse box....having finally decoded the picture clues as to what is where.

Am now thinking wiper switch , altho' every other function works ok, main wipers, washers and rear washer too.

However, as the rear washer works, and there is no rust or other contamination on the motor contacts, the switch seems the only other option.....or another broken wire somewhere else in the system ?

Sadly the Haynes manual does not cover the Estate in its VW Polo version so am now at a loss.

Any ideas or help gratefully received.
Polofrank
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Re: rear wiper U/S

Post by Polofrank »

Follow up ; the switch on the wiper stalk is obviously ok as its operating the relay under the dash, clicking away for all its worth, altho' the rear wiper remains resolutely immoveable.

Am now pretty sure its a failure of power to get from the relay to the motor. Checked the wires in the rear boot/hatch area again and now I'm at a loss to work out where else there may be a break in the wire. Presume the loom must run up along the roof beneath the headlining .

This is getting beyond my scope and think its going to be a job for a qualified motor electrician , unless anyone has any good suggestions ?
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937carrera
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Re: rear wiper U/S

Post by 937carrera »

OK, so the low current side of the relay is working correctly. You need to make sure that the high current feed to the relay has voltage (terminal 30), that when the relay is engaged 12V is coming out of terminal 87 and follow that down the loom to the motor. Finally make sure you have a good earth from the motor

https://www.12voltplanet.co.uk/relay-guide.html

I would be surprised if the rear wiper wiring was different for the estate.
Polofrank
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Re: rear wiper U/S

Post by Polofrank »

Hi, and many thanks for the reply.

The relay in question that controls the rear wiper and in fact it also has an effect on the front wiper too is numbered 174 . From the main agents, NLA, but when it was it was in excess of £50 !

It is unusual in that it has a a "tail"..... a black wire which plugs in to the back of the relay , i.e. the opposite end from where it plugs into the relay board. The 4 terminals are numbered 53 ( which I think is live ) 31 and 15 and just a letter "L " against the last tag which seems to work the front wipers to my surprise.

The two numbered 31 and 15 are the wires that go to the rear wiper I THINK, but am unable to get to the back of the relay board without serious disruption to the underneath dashboard area of my car which I'm reluctant to do.

I bought a second hand 174 relay off eBay and that does not work any better. Also have bought a second hand switch which also does not produce the desired result.

As I do not know which of the two positions, 31 and 15 , are the power wire to the wipers and the other the park power, its nigh on impossible to even attempt a continuity test and as of now am resigned to taking the car to an auto electrician.

I fear its a break somewhere in the power wire but where that could be is anyones guess. If I use a separate battery and connect direct to the wiper motor it works on on the red/black wire plus earth, whilst the grey/black wire plus earth parks the wiper

To add to my electrical gremlins , the low fuel light came on today whilst I actually have a full tank. Maybe co-incidence that I filled the fuel tank full yesterday for the first time since owning the car.......

Have had a couple of these Estates in the past and never come acrsoss any of these issues; failing window motors seem the Achilles heel, but this car is driving me nuts.
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937carrera
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Re: rear wiper U/S

Post by 937carrera »

What you need is a wiring diagram and understanding of DIN terminal numbering.

I can't help with the former for now, but try this

http://www.vintagebus.com/wiring/defs.html or https://www.autoelectricsupplies.co.uk/ ... nal_coding

15 is live
31 is an earth route
53 is live to the motor

Are you sure you have the correct relay and in the correct location - not someone else's mistake ?

Can you post a photo of the relay, with either terminal numbers or better if there is a wiring diagram on the side
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937carrera
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Re: rear wiper U/S

Post by 937carrera »

Maybe this helps - I haven't come across the Polo Variant before
rearwiper.jpg
Polofrank
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Re: rear wiper U/S

Post by Polofrank »

Wow, thank you so much for all that information, and especially that wiring diagram as it certainly matches with the wire colours on the rear wiper motor.

Also the description of the relay and the terminals.

I cannot be sure but suspect this is the correct relay as the small wire that comes from the back of the relay box is obviously meant to be there....there is a special plug that fits into back of it and of course is removable to allow the relay to be replaced. My only fear is that the relay I purchased from eBay may in fact have the same problem that is on the car now.....hence why it was "available".

Not quite sure how to post pictures on this web site , but certainly will try a bit later. Sadly there is no wiring diagram on the side of the relay , altho' I know what you mean as some do have a small schematic printed on to them.

Will see what I can do with attaching pictures of the relay.......
20190504_195311.jpg
20190504_195203.jpg
20190504_195136.jpg
20190502_173511.jpg
Hoping these will come out.

Ah seems to have worked, the first picture is of a second hand wiper switch showing the red connector that takes the signal from the button on the end of the switch to the relay. That is working correctly on the car so I don't think the problem lies with the wiper arm switch.
Last edited by Polofrank on Sat May 04, 2019 8:41 pm, edited 1 time in total.
Polofrank
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Re: rear wiper U/S

Post by Polofrank »

Looking at the wiring diagram, i'm thinking of connecting a test light to the output wire ( Black and red ) at the wiper motor end to see if I get a fluctuating pulse there , I'm presuming it has to be a fluctuation to give the intermittent wipe feature whilst the other wire ( black and grey )returns the wiper back to the parked position......I don't remember seeing the wiper working continuously or am I mistaken ?
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937carrera
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Re: rear wiper U/S

Post by 937carrera »

I'm glad that helps - does this make sense to you ?

The relay should be in the centre of the bottom row of the relay block

So the wire from the switch goes to the connector T1b - correct ?, that provides low current 12v to the relay

Terminal 31 / position 4 on the relay provides an earth for the low current side

Terminal L / position 6 on the relay provides power for the rear window washer pump

Terminals 53 /position 2 on the relay provides the high current connections for the motor

Terminal 15 provides high current connection to the relay

If so you can test the relay with a 12v source and a multimeter.

First of all check the resistance on the relay coil by testing between the connector and pin 31

+ve to the connector at the top
pin 31 to -ve should engage the relay

With the relay engaged you should have continuity between pins 15 and 53, maybe you will need to wait a few seconds if it is an intermittent function

The relay shows a transistor within the scematic. This is probably a small IC which provides the intermittent wipe functionality
Polofrank
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Re: rear wiper U/S

Post by Polofrank »

Thank you so much for your very comprehensive and informative help.

Will hopefully have another look at the car/relay tomorrow , time and weather permitting.
Finleye2000
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Re: rear wiper U/S

Post by Finleye2000 »

On my polo my front wipers completely failed to work on all speeds. Only rear wiper and washers both front and back would work. Turned out the contacts in the wiper stalk were all worn out and shorting across each other. May not be the same in your case though with just the rear not working. Slough I guess if this was happening to you your fuses would be blown.


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Polofrank
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Re: rear wiper U/S

Post by Polofrank »

Appreciate the suggestion, but having bought a second hand unit and connected the stalk up to the bit that triggers the relay, it still fails to work so I "think" that eliminates the wiper stalk on the column.

Worth a thought.

Have tried testing the relay, but unable to produce any reactions, so sadly the reality is I need to take the car to an auto-electrician who understands electrics which is certainly not what I do.
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937carrera
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Re: rear wiper U/S

Post by 937carrera »

You've done the hard yards on diagnosis.

If the relay isn't engaging and closing the high current side that's your problem. New relay and all should be good, remember these are used on the T4 as well as other vehicles.

Try here https://www.stevensvwspares.com/vw-vari ... number-174 or ebay for a used one as new ones seem to be difficult /expensive to get.
Polofrank
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Re: rear wiper U/S

Post by Polofrank »

I'll try that idea, but not sure I was doing the correct actions with the relay to be honest........
Polofrank
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Re: rear wiper U/S

Post by Polofrank »

Anyone need a couple of 174 relays ?

tried two now thinking that the second hand one I bought from fleabay might also be suspect. No such luck and the new relay clicks away like the other two so definitely not the relay. Convinced now its a break in the wire between the relay and the rear motor which I know works if connected directly to a battery.

Three phone calls to a local auto electrician have resulted in no replies.

Cornwall is a wonderful and most beautiful area to live but there is a dearth of super experienced auto experts here when it comes to something a bit unusual. If you can plug in to a diagnostic socket, then its fine, but old school experts are rare as rocking horse poo.

Sadly, my expertise is not good either. The only answer left from what I can see is running a new supply the length of the car to the rear wiper motor via an independent switch. Not ideal but a possible solution.
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