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In dash boost gauge install


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#1 Hoosierquest

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Posted 13 June 2018 - 11:16 AM

Hey guys. Trying to install a LED backlit boost gauge in dash and would like to tie it into the existing dash lighting for dimming purposes. I have found that the black/yellow and green white wires on the lower right connector seem to be tied into the cluster lights.  
Is one of these considered positive and the other negative?  If so which one?  
I know with typical incandecant bulbs or won't matter but I believe LED's are polarity sensitive.
When I used my meter on the chassis side both wires seemed to go to ground I assume this has to do with the dimmer?  
Any insight?
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#2 techboy

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Posted 13 June 2018 - 11:58 AM

I haven't done what you're trying to do, so I can't speak to the dimmer wiring on the console, but I can confirm what you're saying about LEDs.  I work with them all time (at work) and they definitely have polarity.  If they're loose you can usually tell by looking at the legs ... the shorter one is always negative.  If it's already built into a component, like your boost gauge then you might have to experiment.  Hooking it up backwards won't hurt it - it just won't work.
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#3 SA22C

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Posted 13 June 2018 - 12:39 PM

LED's are polarity sensitive.

In order for them to be dimmable you must utilize a PWM (Pulse Width Modulator).



Edited to ad:
If you cant get the LED to come on at all wired either way, its probably because it isnt seeing the proper voltage due to the stock dimmer.
A PWM wired into the stock wiring most likely wont work either due to different voltage requirements. Most likely you will have to run a dedicated circuit with the PWM.

Edited by SA22C, 13 June 2018 - 12:45 PM.


#4 Hoosierquest

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Posted 13 June 2018 - 03:53 PM

I got it to work by using the G/W wire as positive and B/Y as ground. Would not work the other way around. However I get no dimming feature. This is the same connections that goes to both sides of each side of the factory cluster lights. Does the lack of dimming have to do with the nature of the LED?  The rest of the cluster still dims.

Edited by Hoosierquest, 13 June 2018 - 03:54 PM.

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#5 SA22C

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Posted 13 June 2018 - 04:24 PM

View PostHoosierquest, on 13 June 2018 - 03:53 PM, said:

I got it to work by using the G/W wire as positive and B/Y as ground. Would not work the other way around. However I get no dimming feature. This is the same connections that goes to both sides of each side of the factory cluster lights. Does the lack of dimming have to do with the nature of the LED?  The rest of the cluster still dims.

That is what the PWM is for. LED's use pulsed voltage as opposed to constant like a traditional bulb. The PWM makes the constant voltage pulse at slower or faster intervals making the LED dimmer or brighter, respectively. The gauge will probably light up full power and not dim as you turn the dimmer knob, and then go out completely.

#6 Hoosierquest

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Posted 13 June 2018 - 04:38 PM

Gotcha. I see that auto meter sells a separate dimming device. Ugghh. Another 30-40 bucks.
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#7 SA22C

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Posted 13 June 2018 - 04:44 PM

View PostHoosierquest, on 13 June 2018 - 04:38 PM, said:

Gotcha. I see that auto meter sells a separate dimming device. Ugghh. Another 30-40 bucks.

You might be able to find an LED retrofit bulb that has a dimmable driver.    If not... wiring in a PWM would be super easy and relatively cheap  ( ~10.00).  The only problem with the separate PWM would be the fact that you would have a dimmer switch for nothing else but the boost gauge.




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