UK-POLOS.NET - THE VW Polo Forum

Again I have spoken too early. The washer is working but the wiper is not. The fuse seems to be OK. Looking at some of the electrical block connectors at the rear where the washer tube was disconnected there is some green staining a bit like copper oxide (the connector at the top of three block connectors located there). Would that be the rear wiper connector?

Yes rear wiper and boot lock

Just getting around to attending to the non functioning rear wiper (washer is OK).

I guess I need to check for a voltage at the connector in the boot to rule that out then likely the motor is faulty?

yes, turn the wiper on, then check for voltage (bearing in mind itll pulse)

One suggestion to stop you being “mugged” by test probe results, if you try unplugging things and probing into connectors for evidence that power is getting through, and find 12volt while the load has been removed, always remember that there is a good chance that that supply line has been chopped almost completely through, but as the load has been removed and so no current is flowing you will still see 12volts, reconnect load and the high resistance of a chopped lead will drop the voltage at the load down to next to nothing so the motor will not turn! That might not be your problem but always bear that in mind when fault finding.

Thanks RUM4MO. Are you suggesting the supply line might have been chopped when I had the inner tailgate cover off?

The wires can break inside the rubber tube between the body and the tailgate. ive seen that a few times now

No, just as Alex says, the only things to get chopped when you remove that trim is your skin and temper!

I put off fixing the rear wiper (washer works) but now the weather is turning I need to get on with it. What I've also discovered is that the rear demister is not working. I guess the electrical connector in the boot near the washer bottle also feeds power to the demister? Fuses look OK on both wiper and demister. What else could be wrong?

I’d say broken wires. Do a multimeter test between the positive on the rear demister and it’s ground. Then between the demister and a ground in the boot instead and see if it has power

Will do. Is there any chance I could have chopped something reinstalling the tailgate interior trim panel? I can't recall anything that would have fouled against the wires.

No, they all run on the inside and nothing is as such exposed or damageable like that

Thought I'd have a look at these before the weather turns. Removed the rear tailgate panel and found nothing untoward. Switched on the rear wiper (washer works) and found put a tester on the four conductor plug that goes into the wiper unit. Found 5V and 11.3V. Would this suggest the motor unit (Valeo) is at fault? There had been a leak in the boot area around the connectors by the seat belt (rear n/s) but no fuses had blown.

As for the rear demister, again found no obvious chopped wires (not to say there aren't any). Released the plastic side trims from the upper tailgate just enough to see a flat wire and metal tab/conductor that connects to the element at each side. Just realized I should have checked the voltage across these, but the voltage from each side to ground was approx 0.38V with engine on and demister on.

I've checked again and found the following:

11.67V (approx) across the rear demister element (measured at the metal tab on each side).

No voltage at the wiper motor with the ignition off (11.67V approx with it on).

This would suggest problems are local to the accessory?

In case of the demister, will need to check this again in the morning to determine if it is operating or not. Could anything contribute to an intermittent operation? Would a break in a single element across the rear screen cause it to stop working or not?

As for the rear wiper, it seems the motor (a Valeo unit) must be at fault?

A break in a single line will just disable that line

Thtats normal - no voltage with the ignition off.

Have you got a spare motor at all?