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Rear Defrost not working after Heated mirror DIY


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Hi all,

So it came in my mind to install heated mirrors, because they didn't come with my Toyota Yaris 2017 (Mk3, 1.5l petrol, europe)

Everything went good, wires from mirror to center console where the rear window defrost/defogger button is, and it worked, (right mirror was heating up, as it should)

Now I did the same for my driver side, connected the mirror, I turned on the rear defrost/defogger, and nothing. Button not working anymore, I opened the center console and the switch had a electronic burning smell.. (I first checked the fuses but nothing was blown)

Why didn't the fuse blow but the button itself did? Did I do something wrong? 

Does polarity matter for heated mirrors? (I think not because of DC power but I could be wrong). The mirrors doesn't come with + and - Signs so how am I supposed to know which one goes where?

Partnumber is 5590375F604 btw

16575469845071073831509445843513.jpg

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You shouldn't wire directly to the switch, as it is a low voltage circuit designed to switch a relay controlling the higher voltage circuit required for the heating element hence the burning smell you experienced as you pass too high a current through the switch.

The switch shares a 7.5 amp fuse with the AC so check this , whereas the defroster has its own 30 amp fuse and the mirrors should have there own 10 amp fuse.

The polarity of the glasses is not an issue.

image.thumb.png.440348517192bc0c9f7474cd5433e386.png

 

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Sorry I really don't understand such wiring diagrams, but I was fiddling around with the knob  on the inside today  and then suddenly my ac didn't  work, so Just as i thought, the ac fuse 7,5A was blown, I don't  know why. But then because I have no spare fuses left I used the MIRROR heater fuse 10A for the AC (I think it's  safe to use that fuse because there were no heated mirrors from the factory on my car)

But now that I think about it, why is there a HEATED Mirror fuse even if I don't  have it? It it connected to something else that I don't  know about?

 

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And I can buy a secondhand switch, but I don't  know if it will burn the switch again when I hook everything together. Is there another place in the car which can support the high current from both heated mirrors which is connected to the rear defrost button?

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If you're not lucky you have killed the A/C amplifier/integration relay, buttons in cars for the last 15+ years are just a user interface these just control a module that in turn controls the device in this case a heated mirror

Disconnect any wiring you have connected to that switch, its a fire risk

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7 minutes ago, flash22 said:

If you're not lucky you have killed the A/C amplifier/integration relay, buttons in cars for the last 15+ years are just a user interface these just control a module that in turn controls the device in this case a heated mirror

Disconnect any wiring you have connected to that switch, its a fire risk

I soldered the heated mirrors to the the positive and negative for the switch, I thought it was safe..

Is there another place where I can solder the heated mirrors to while still keeping the defrost button to turn on and off the heated mirrors?

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The easiest way is just to connect the mirrors in parallel with the heated rear window. When that is on the mirrors are on.

This means you connect one terminal of each mirror to ground and the other terminal on each mirror goes to the 12 volt feed to the rear window glass. 

You should fuse the mirrors separately for safety.

 

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Oh, luckily I didn't wasted all my time on the wiring then, only have to come out of the dash and go trough the lower footwell trim all the way to the rear window.

Where is actually the terminal on the rear window glass? And If I connect both mirrors to there, nothing burns out around that terminal?

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The glass normally has a terminal at each end (left and right of the glass). One will go to ground (0 volts) and the other will go to the switched 12 volts from the relay.

All you need do is pick that switched 12 volt wire up which runs from the glass back to the relay.  

 

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It should be fine. The 12 volt feed to the glass is via a high current relay and 30 amp fuse. The diagram from earlier shows the path. The relay is top right of the diagram. Each mirror will draw (at a guess) a couple of amps at most.

Any 'risks' will be down to how you implement your own wiring. It must be safe, connections secure, suitable wire and not be able to chaff against anything.

It should be fused closest to the end where the wire connects to the switched 12 volts to protect the whole length of your additional wiring. 

  

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So if I connect it even with the few ampere's increase, it should stay under 30A. (I really don't want to blow that one because I really don't  know what kind of a fuse Toyota uses for those high Amp fuses (kinda block)

I do crimp the wires to wire terminals, have a heatshrink on the terminal and if I don't  feel save I also even use electrical tape. Around sharp edges I do secure the wire and making sure it does not rub on anything metal.

About the fuse, If I use my own fuse in the middle of the wiring, is it then seperated from the 30A fuse or how does that work?

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Personlly I woud feed my wires through the existing door grommets.

Fit fuses as close as possible to your take off point.

If you decide to cut the rear heater then you can insert two fuses just use your own 25 amp fuse for heater and a 2 amp for each mirror.

If you need heat shrink tubing but are worried about the heat from heat gun or soldering iron then use silicon sealant and slide the tubeing over then tutch up the ends to stop dampness getting in.

PS heat shrink tubing can be replaced with any tubing you removed the wires from.

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28 minutes ago, Derek.w said:

Personlly I woud feed my wires through the existing door grommets.

Fit fuses as close as possible to your take off point.

If you decide to cut the rear heater then you can insert two fuses just use your own 25 amp fuse for heater and a 2 amp for each mirror.

If you need heat shrink tubing but are worried about the heat from heat gun or soldering iron then use silicon sealant and slide the tubeing over then tutch up the ends to stop dampness getting in.

PS heat shrink tubing can be replaced with any tubing you removed the wires from.

I already have them trough the rubber door grommets, but i meant from under the pedals trough the side of the car where u step in ur car to the back.  

No i'm  not cutting anything but my I meant; the rear defogger has a 30A fuse, do the heated mirrors take Amps from the 30A fuse or does it run seperatly from the fuse I plan to use between the wiring?

That's  something I still don't quite understand

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9 hours ago, mmisch said:

So if I connect it even with the few ampere's increase, it should stay under 30A.

It should. The rear window will not draw 30A and in any case, if you look at the diagram you can see that the 30A fuse also feeds the mirrors.

 

9 hours ago, mmisch said:

About the fuse, If I use my own fuse in the middle of the wiring, is it then seperated from the 30A fuse or how does that work?

The fuse should really be as close as possible to where you add your wiring to the 12 volt supply. The fuse is there to protect the wiring. The fuse only protects from the point it is inserted into the wiring. Anything before the fuse is not protected.

 

7 hours ago, mmisch said:

do the heated mirrors take Amps from the 30A fuse or does it run seperatly from the fuse I plan to use between the wiring?

They do. The 30A fuse sets the limit of protection to the that circuit. You can add additional feeds off that fused 30A supply as long as you do not exceed the overall 30A rating. A typical heated screen will draw somewhere around 12 to 18 amps, well below the 30A limit. 

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2 hours ago, Mooly said:

It should. The rear window will not draw 30A and in any case, if you look at the diagram you can see that the 30A fuse also feeds the mirrors.

For me the diagram is a bit pixelated so I can't  read the text in them.

Okay, so the additional fuse is there only to protect the wiring, got it.

I will try to do all this shortly but first need to wait for the new heater switch/knob.

When does actually the additional Fuse blow that  I plan to use? In what occasion?

And about the big blocky Toyota fuses just like the 30A one, how do u actually replace it? Is there a name for this fuse?

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The 12v comes in at the top right (30A fuse) and is switched by the relay below it. From there it goes to the heated window below.

The green path shows the route to the mirrors. The 10 amp mirror fuse is at the top left (2nd box in from the left). From there it goes to the mirrors.

 

2008321924_Screenshot2022-07-12085208.thumb.jpg.8b4731fa79ac8405d32d68da4ef06183.jpg 

 

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36 minutes ago, mmisch said:

And about the big blocky Toyota fuses just like the 30A one, how do u actually replace it? Is there a name for this fuse?

These fuses i meant which he's pointing at

Screenshot_20220712-102628.jpg

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The mirrors are fuse down to 10 amp the wiring is in place, the fuse holder is there, no need to run cable

connect the mirrors to the pin on the AF4 connector

I will post some info shortly

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I did have a 10A fuse for heated mirrors but the car didn't have heated mirrors standard. That's why I was okay with running my own wires. 

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You don't need to touch it !! Please listen

what wires have you got at the mirror plug and socket on each door - take a picture

Also, a picture of the footwell connectors

eg.

1912781320_IMAGE2022-04-05163456.jpg.372

 

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No I know, but but u told me something with the AF4 connector, but not much. I don't  know what that is, I just want to have the heated  mirrors working when I press the rear defrost button without blowing up anything again. 

I will take a look and take a picture when I have free time again 

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Footwell wiring i can take, that is just pulling trim, for the mirror plug I don't  have time yet

20220712_141428.jpg

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