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Illumination wire options

Posted: Sun Apr 20, 2014 8:41 pm
by Roadrunner
I have replaced the headunit in my SE and wired the illumination wire to the factory spot.
I have since installed a boost gauge that requires wiring into 12v/earth/illumination so I tapped into the headunits IGN and illumination wires, but now have a very low volume hum through the speakers with the headlights on.
I want to separate the gauge illumination wires from the HU wires, but where else can I tap into IGN and Lights? This would need to be illumination not connected to the dimmer (the instructions say not to)

Re: Illumination wire options

Posted: Mon Apr 21, 2014 8:46 am
by Magpie
Most gauge installation instructions advise against using the same ground as the stereo as well as ones that share power with the vehicle’s stereo, ignition system, and fuel pump

Re: Illumination wire options

Posted: Mon Apr 21, 2014 9:06 am
by sailaholic
Tap the park lights


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Re: Illumination wire options

Posted: Mon Apr 21, 2014 2:42 pm
by Roadrunner
Magpie wrote:Most gauge installation instructions advise against using the same ground as the stereo as well as ones that share power with the vehicle’s stereo, ignition system, and fuel pump


Yeah they are separate earths but the stereo was out at the time and access was easy so temporarily tapped into acc and illum there.
Having a look around I'm not sure what wires are what under the dash and what wires are for illumination but not connected to the dimmer.
Alternatively I guess I could just connect the illumination wire to the acc wire and have the lights on all the time, but I'd rather not.

Re: Illumination wire options

Posted: Mon Apr 21, 2014 2:43 pm
by Roadrunner
sailaholic wrote:Tap the park lights


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Do you know which wires these are? Ie where and what colour under the dash

Re: Illumination wire options

Posted: Mon Apr 21, 2014 3:04 pm
by taminga16
Trace the required cable from the fuse block.
Greg.

Re: Illumination wire options

Posted: Tue Apr 22, 2014 12:31 am
by and1
I tapped the dimmer switch for illumination. Use a multimeter and find the 2 wires of the 3. One will be the ground, one the illumination 12V and the other a variable resistance corresponding to the dial position of the dimmer. Use the 12V and ground.

Re: Illumination wire options

Posted: Tue Apr 22, 2014 2:55 am
by Okibi

Re: Illumination wire options

Posted: Tue Apr 22, 2014 1:40 pm
by Roadrunner


That looks great! So just plug it into where a 15amp fuse is in the fuseblock and away you go?

I might however look at tapping the dimmer switch as and1 suggests, but would this mean the gauge lights will be on as soon as the gauge gets 12v power regardless of if the car lights are on or not?

Edit: Dont worry having a moment :oops: I know what to do and where to connect too :)

Re: Illumination wire options

Posted: Tue Apr 22, 2014 3:15 pm
by Nevyn72
Roadrunner wrote:


That looks great! So just plug it into where a 15amp fuse is in the fuseblock and away you go?

Agreed, that's why I just ordered 2 of them this morning! :mrgreen:

I probably won't use them long term, but they will be great to test circuits to make sure the one I want to tap is the right one! :wink:

Re: Illumination wire options

Posted: Tue Apr 22, 2014 5:54 pm
by Roadrunner
Ohh Jaycar have them for $4.95 each and I can get them now instead of two weeks time. Might pick some up this afternoon for the upcoming weekend.
I'm at work and cant remember, does the MX5 use standard fuses or the mini ones??

Re: Illumination wire options

Posted: Tue Apr 22, 2014 5:57 pm
by Nevyn72
Roadrunner wrote:Ohh Jaycar have them for $4.95 each and I can get them now instead of two weeks time. Might pick some up this afternoon for the upcoming weekend.
I'm at work and cant remember, does the MX5 use standard fuses or the mini ones??

Standard in the engine bay fusebox, mini in the dash fusebox. :wink:

Happy to buy from the 'Bay as I don't need them in a hurry, doing some engine bay mods first......

Re: Illumination wire options

Posted: Tue Apr 22, 2014 6:58 pm
by Roadrunner
Eh what's a few dollars for convenience :)
I drive past a jaycar on the way home from work :D

Re: Illumination wire options

Posted: Fri Apr 25, 2014 7:42 pm
by Roadrunner
Reporting back that those jumper leads work a treat.
Tapped into the cig lighter fuse (gauge wire on a 10a fuse) tapped the dimmers illumination wire and ran new ground.
All perfect, no more hums or buzzing through the stereo and I got to use my soldering iron again :D

Re: Illumination wire options

Posted: Fri Apr 25, 2014 10:37 pm
by KevGoat
Very cool. In all the car wiring I've done, I'd not come across those jumpers! So simple! Be remembering those for future projects ...

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