Make a wiring loom for heated mirrors

Hi all - I picked up some headed mirrors from MUDstuff and new mirrors secondhand/new.

However it has not got the wiring harness. I have done some research on how to fit the mirrors neatly, but would someone be kind enough to make an idiot proof guide to making the wiring for the mirrors. On a tight budget here! - The proper switches are coming in at £25!! I want to put in a rear working light as well - so that is another £25 for that switch! Madness!

Many thanks

Earl said:

Hi all - I picked up some headed mirrors from MUDstuff and new mirrors secondhand/new.

However it has not got the wiring harness. I have done some research on how to fit the mirrors neatly, but would someone be kind enough to make an idiot proof guide to making the wiring for the mirrors. On a tight budget here! - The proper switches are coming in at £25!! I want to put in a rear working light as well - so that is another £25 for that switch! Madness!

Many thanks

Click to expand...

Why not purchase carling switches? They have multiple configurations, and face/LED colours. They can be had for a few £.

In terms of a “wiring harness”, you only need 2 wires to go to each heating element. A live (any colour you want, and can recognise when doing diagnostics later), this should be fed from a relay that the switch makes. Then an earth, usually black, to a reliable earth point not the body.

The elements are only around 2 amps, so 1mm wire work, but I would use 1.5mm. It should be easy enough to wire in.

mick 1986 said:

Why not purchase carling switches? They have multiple configurations, and face/LED colours. They can be had for a few £.

In terms of a “wiring harness”, you only need 2 wires to go to each heating element. A live (any colour you want, and can recognise when doing diagnostics later), this should be fed from a relay that the switch makes. Then an earth, usually black, to a reliable earth point not the body.

The elements are only around 2 amps, so 1mm wire work, but I would use 1.5mm. It should be easy enough to wire in.

Click to expand...

That is very helpful, thanks - (embarrassingly) Could you let me know what kind of relay and which wire goes where. I have used a relay before, but just followed instructions.

I know i can get cheaper switches, that can look nice, but I like the OEM look.

Thanks for your help

Earl said:

That is very helpful, thanks - (embarrassingly) Could you let me know what kind of relay and which wire goes where. I have used a relay before, but just followed instructions.

I know i can get cheaper switches, that can look nice, but I like the OEM look.

Thanks for your help

Click to expand...

No problem.

I would take some 2.5mm wire from the battery, but make sure you fuse it at the positive terminal. Personally I would use a 5A fuse (leave the fuse out of the fuse holder until you have wired it all up).

Purchase 30A relay.

If you look at the relay you have just purchase, it should have a pinout diagram with it. They should be 30, 85, 86, and 87.

Take this new battery feed to a 30A relay, (standard relay size available at Halfords or other motor factors), to pin 30.

Pin 87, is your feed out to the mirrors, so this will have 2 wires, one going to each mirror.

Pins 85 and 86 are what you use to switch the relay closed. One of the pins needs connecting to a decent earth point, the other is what you wire your switch feed to. If you make the switch wire ignition switched, it can’t be left on and flatten the battery.

Have a look at this picture.


Substitute 87 driving light bulb, with heated mirrors.
Substitute 86 from main beam, with output from switch.

You could get fancy and fit a timer relay that will need a “one shot” switch, but it’s over complicating the wiring install.

mick 1986 said:

No problem.

I would take some 2.5mm wire from the battery, but make sure you fuse it at the positive terminal. Personally I would use a 5A fuse (leave the fuse out of the fuse holder until you have wired it all up).

Purchase 30A relay.

If you look at the relay you have just purchase, it should have a pinout diagram with it. They should be 30, 85, 86, and 87.

Take this new battery feed to a 30A relay, (standard relay size available at Halfords or other motor factors), to pin 30.

Pin 87, is your feed out to the mirrors, so this will have 2 wires, one going to each mirror.

Pins 85 and 86 are what you use to switch the relay closed. One of the pins needs connecting to a decent earth point, the other is what you wire your switch feed to. If you make the switch wire ignition switched, it can’t be left on and flatten the battery.

Have a look at this picture.
View attachment 169099

Substitute 87 driving light bulb, with heated mirrors.
Substitute 86 from main beam, with output from switch.

You could get fancy and fit a timer relay that will need a “one shot” switch, but it’s over complicating the wiring install.

Click to expand...

That is supremely helpful, thank you! Interesting Bearmach only seem to have 40a ones - But i will get a 30a one as recommended! If i don't make a hash of it I will put some pics up to help other members out in the future

Earl said:

That is supremely helpful, thank you! Interesting Bearmach only seem to have 40a ones - But i will get a 30a one as recommended! If i don't make a hash of it I will put some pics up to help other members out in the future

Click to expand...

I wouldn’t buy from Bearmach. They are overpriced for the cheapest gear.

Been thinking of fitting heated mirrors to mine. Had an idea of linking them in to the heated rear window relay as they use little power.

tottot said:

Been thinking of fitting heated mirrors to mine. Had an idea of linking them in to the heated rear window relay as they use little power.

Click to expand...

and on one switch haha

https://www.12voltplanet.co.uk/adjustable-delay-timer-relay-delay-on-or-off-12v-10a.html

A bit expensive, however, a momentary switch and your heated mirrors come on for 10 mins then automatically switch off again, you dont have to worry about them, there are other relays out there that may suit your needs better, use an ignition switched live or trigger it via your rear window demist.