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RoyTheBoy

Rewiring mirror heater to heated rear window

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RoyTheBoy

Hi, I'm wondering if anyone has done this yet and has any information/diagrams. As I always tend to forget to turn off the heated mirrors, I have to turn the mirror switch to either right or left as if I'm adjusting the mirrors but I forget and keep it in the central/heated position, thus costing more in fuel. In my Peugeot the heated mirrors and rear window heated element are on the same switch. I want to rewire the mirrors heated part to the rear window switch, any advice would be grateful thank you. I'm thinking would be easy but thought I'd check on here first. I have a VW Polo match 60 9n3 2009. Thanks.

 

Also I'm planning on fitting an outside temperature guage inside the mirror and wired to the car battery somehow if anyone has done this too as I miss this function.

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nige8021

I think you'll find the mirror heat is only applied if the rear screen heat is switched ON as the HRW switch just supplies a ground to the onboard power supply unit and the mirror heat switch also only provides a ground to the same unit and this then sends the 12v out to the HRW and if the mirror switch is also selected then the power goes out to the mirrors as well.

 

As to saving fuel, the mirrors probably consume less power than the radio at full volume 

 

Depending on your dash panel it might only need the sensor to be added behind the front bumper to get an OAT display 

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RoyTheBoy

On my car the heated mirrors work, get heated with the heated rear window switch turned off, just wondering if I can just cut a wire or 2 and solder on rear window switch instead. 

Here's a pic of my dash. 

I have updated my radio since I took this pic. Thanks Nige 

Screenshot_20200213-001925_Gallery.jpg

Edited by RoyTheBoy

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RoyTheBoy

How would I know if I only need the sensor fitted in the bumper, wouldn't of thought would display on my dash.

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nige8021

TBH I wouldn't bother, you would need to do the wiring mod at the CCM not at the HRW switch. 

 

I don't know without seeing what options the CCM gives if you do a "long-coding" with VCDS it might just be a case of doing a bit of re-coding so they only come on with the HRW  but even if this was possible there wouldn't be any perceivable fuel savings even if you left the mirror heat on permanently 

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nige8021
3 minutes ago, RoyTheBoy said:

How would I know if I only need the sensor fitted in the bumper, wouldn't of thought would display on my dash.

 

Depending on your speedo some did have an OAT display on them, the sensor is mounted behind the bumper cover on the passenger side 

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RoyTheBoy

I've changed my ccm to a remote locking one, would of thought would be a simple solution, taking mirror off, cutting and adding wires from heated part and running them to other switch or rewire it straight to battery via a switch somehow with a 10 minute cutoff, with a fuse fitted. I'm thinking they'll last longer if not on all the time, not only for fuel savings. I may not bother but it'll give me something to do.

Don't think mine has a oat display, I'll post a pic of my display tomorrow if okay, I'll look into it. Thank you 👍 

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nige8021

Seriously don't bother there will be absolutely no fuel saving and as the car is 10 years old if the mirror heaters are still working chances are they will last another 10 years and a replacement is about £5 if you search ebay

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Yeti

I'd have thought if you have air con you'd already have the external temp sensor. Does your car have the two buttons in the end of the wiper stalk for stepping through displays on the clocks?

 

I'm 90% sure that the mirrors don't heat unless the heated rear screen is on on my Fabia, and that has it's own 10 minute timer. Can't imagine it being different on the Polo. I think the 2k Caddy is the same as well. 

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RoyTheBoy

Mine has no button on the stalk just the reset Mileage button where the speedos are that you can turn left and right to set the clock, deffinatelly not got the oat function, I thought Nige meant that the manufacturer left the display part there on some models. 

And the heated mirrors is deffinatelly turned on without the rear window heater turned on. You can hear the relay click when u turn it on and off and yes it does get warm. 

And it says in the owners manual to make sure to turn the heated mirror off to SAVE FUEL, so whys it say in manual I'll be saving if I won't be.

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nige8021

Well that's odd, as there is no relay shown in the dealer wiring diagrams for the mirror heat, only the HRW ??

 

The mirrors will only be pulling a couple of amps at most, there's not even a separate fuse for them, the owners manual will probably tell you to all sorts nonsense to save fuel, just to make their claimed mpg figures.

 

The OAT display would of been standard on some versions like if you have climatronic AC not the manual version you have

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RoyTheBoy

I don't know how it works but there's a definite click when I turn it on and off, sounds like it's coming from under the dash as if it's a relay so I'm guessing it's a relay of some sort, I haven't got cruise control either. I only bought this car due to its very low mileage and from someone we know and want to add a few tweaks to it, there's nothing wrong with that is there. 

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Yeti

The problem with modern cars is everything is so integrated, you run a risk of affecting a totally different system, especcially if you're in the dashboard. I think if I were trying to do that, I'd go in between switch and the mirrors, and probably go with a delay relay like this. No idea if it would work though. 

 

https://www.12voltplanet.co.uk/12v-universal-heated-rear-window-timer-relay-10-min-delay.html

 

I'm all for playing about and making a car your own. I don't think you're going to get much of a fuel saving though. I can run around with a 300W invertor in the boot charging my laptop and cordless tool batteries and not notice any difference in economy. 

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RoyTheBoy
16 hours ago, RoyTheBoy said:

Thank you Yeti and Nige. 

Years ago I had a 1000 watt amp in the boot with bass box fitted and I didn't notice the difference, but I've started using a mpg app now, I was thinking of somehow fitting a buzzer to the switch too with a 10 min delay relay to remind me to turn it off. I'm sure it's no big deal just leaving it alone but I'll still have a look into it lol. I've risked rooting phones, getting them the way I like it, bricking one but learned from my mistakes. 

I thought if I tested the voltage of the wire when turn on the mirror heater and hrw and if both the same voltage and both use same wire as in positive or ground at the switch and using resistors if voltage different it would be okay. Don't fancy knackering the electrics of my car up though. I've bypassed airbag lights with resistors before now and no problem lol. I think imo airbags are more dangerous anyways. Thanks for the advice and link. I'll have a look thanks. 

 

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nige8021

The HRW & Mirror switch just put a hard ground into the CCM

 

I would check the voltage at the HRW & mirror and see if they do automatically switch off after a time delay as @Yeti said like his Fabia as they are basically the same car

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RoyTheBoy

Nige I've decided to leave the heated mirror alone, spoke to few mates and everyone saying it won't use much fuel and not worth the hassle and not wanting to knacker anything up, thanks for the replies. I'll just add a outside temperature thing, the hrw cuts off after a delay but not the mirrors.

Thanks guys

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Yeti
5 hours ago, nige8021 said:

The HRW & Mirror switch just put a hard ground into the CCM

 

I would check the voltage at the HRW & mirror and see if they do automatically switch off after a time delay as @Yeti said like his Fabia as they are basically the same car

 

I've just done a bit of further investigation on the Fabia, and after checking the various orders you can press the switches in, I've figured out the following:

 

My heated mirrors don't work.

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RoyTheBoy

@YetiThanks@YetiThanks for looking, hope it's an easy fix for you, might be the switch or break in wire, do the electric mirrors work?

I'll try that see if mine presses in too, don't think it will though.

 

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RoyTheBoy

Sorry couldn't delete the "@yeti" parts for some strange reason, tried logging out and back in, even tried editing it but stays there lol

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