Wiring for demister switch

[grayme]

Hello, hopefully a simple one but I have done a lot of searching and come up blank.

Son's '08 1 litre Aygo's rear windscreen doesn't seem to work at all.

Fuse is fine, I have put a multimeter to the metal connecters across the window and getting no voltage, which suggests no power getting to it at all?

Switch seems to have been replaced as the light doesn't fit nicely in the switch light's hole, but it does light up when pressed.

Looking on a YouTube video and an eBay advert for a switch where they have cut the wires off leaving a little length, it seems to me that the white and black wires are connected incorrectly; but I cannot find anything that confirms this.

Anyone able to confirm if the wires should be switched over, or at least if doing so is not going to do any damage if it shouldn't have been so?

Thanks in advance 😊

[flash22]

check the resistance and continuity between the 2 terminals on the glass, then the negative and a body ground, these valeo switches are a well known failure point in many PSA cars

i take it you have checked the 20a DEF fuse and the DEF relay

 

a quick look at the diagrams shows 3 wires on pins 1, 2 and 3 - black is illumination 12v, Red is 12v control side, White with black stripe in ground

verify the black/white to a body ground

 

Do the reverse lights work ?

Can you feel the DEF relay click when the button is pressed ? the DEF relay is well and truly buried in R/B No. 5

pic courtesy of @WillBox - item in the red circle is the immobilizer, R/B No. 5 is just above it

click to enlarge

 

[grayme]

Thanks.

Reversing lights work and there is no resistance between the terminals on the glass.

Which pins are 1, 2, and 3 please?

Looking at the other points right now.

Both black and white have no resistance to ground.

R/B 5, is that a dashboard removal thing?

Red gives 12v when switch is on and illuminated.

[flash22]

You can get to R/B No. 5 from the footwell, but it's not easy

red giving 12v means the switch is working, the switch controls the control side of the relay

Pin 1 is black

the diagram shows 2 connectors, one in the driver's side upper dash and the other is on the passenger side c pillar

do you have continuity across the defog element ?

 

[grayme]

I've taken the dashboard off an X5 (to change the heating / cooling fan), that was a bit of a hassle 😆

My top picture has white, black, red, which suggests that isn't right. But if I swap black and white the light doesn't work. 

Should it be black, red, white?

I'm afraid I don't understand 'the diagram shows 2 connectors, one in the driver's side upper dash and the other is on the passenger side c pillar'

There is continuity across the defog element as there is no resistance between the two window terminals on the glass?

[flash22]

There are 2 connectors in the wiring loom one is on the drivers side, the other is on the c pillar - the switch is wired correctly i have found a different diagram

 

 

2 - 12v In from back up fuse

3 - Negative (white)

4 - switch neg to relay

 

the wiring diagrams are listed the other way around

[flash22]

I worked it out, Your pic in your first post is the AC switch !!!!!!!!! 84660-0H010

The defog switch is green, as is the plug 84790-0H010

it's more than likely got swapped over when the stereo was changed

[grayme]

The switch on the air con (which doesn't work, but I suspect that is more down to how the condenser is shot) is green!

We don't switch on the air con as a result.

So I just swap the two over... popping out to see right now!

[flash22]

a/c only works if you press the defrost button LOL, some swapped the switches 🤪

[grayme]

OMG, putting on the 'air con' put on the demister 😊

Thank you, this explains why the 'air con' wiring looked like it should for the demister.

Next step is the metal paint to fix the broken strips.

Thank you so much!

Incidentally, I put the stereo in and replaced the original one, and I didn't touch the switches, so no idea why they were swapped 

 

[flash22]

But does the A/C work - well that's another for the books I guess

[grayme]

I don't think it does, but that's based on having actually having been turning on the demister, seeing the Aircon not get cold (remember when it was hot? 🤭) and looking at a very sorry looking condenser unit. Next time I'm with him I'll try the Aircon by pressing the right button.  😊