How do dimming interior/stereo lights normally work in an automobile? - diyAudio
Go Back   Home > Forums > General Interest > Car Audio
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 20th March 2004, 04:51 AM   #1
diyAudio Member
Join Date: Oct 2002
Location: Pennsylvania
Question How do dimming interior/stereo lights normally work in an automobile?

I am having trouble with some gauges I am putting in my car. I have a Subaru, and as I recall, Subaru uses a moving ground for dimming interior lights, not a moving source.

This gives me troubles, because in my gauges the dimming circuit and the gauge servo power circuit share the same ground. Thus, when I dim my lights, my gauges don't receive enough voltage to operate properly. This annoys the **** out of me; I go to dim my interior lights and the gauge needles fall down.

I would like to fix this problem with a circuit workaround, but I'm unsure where I should start.

The first thing I have to do is find out what is normal for a dimming wire in an automobile. Is the voltage range 0-12 Volts, 11-12 Volts, etc... I don't know what the "standard" voltage difference between fully illuminated and unilluminated is in automobiles.

Next, I have to take some measurements from my car, and find out what the voltage difference between fully illuminated and unilluminated is for my particular application.

Finally, I need to make a circuit that operates on the voltage difference of the moving ground, and transfers that to an equivalent voltage difference on the positive side. Then, I should be able to have the gauges dim correctly while operating correctly.

I've done a ton of custom work on the gauges for my car. I've redone the gauge faces to match the interior of my car, did custom work on the gauge housings, and hooked an 86 db Piezo buzzer to warning lights on my gauges so I get a loud warning if something gets too hot or too low (a big thanks to diyaudio on this design as well). Getting the gauges to dim correctly is that last thing I have to do.

I've spent a ton of time on these gauges, but I've learned a lot about circuit design and have enjoyed every minute of it. I hope I can solve this one last little nagging issue and then the gauge project part of my car will be complete. All that's left then is to tweak the suspension, get her up to 350-400 HP, and get the datalogger in place. Then you can find me on the track

Click the image to open in full size.
  Reply With Quote
Old 23rd March 2004, 12:25 AM   #2
Bose(o) is offline Bose(o)  Canada
diyAudio Member
Join Date: Dec 2001
Location: Ottawa, Ontario, Canada
Usually fully illuminated lights are running from 12V. Not sure about anything else you have a circuit diagram?

Anyway, from one car guy to another....I like the machine you've got...hopefully you can finish everything!
ERTW 4 life!
"the day has 24hours. If that is not enough take the night."-Roemhild
  Reply With Quote
Old 23rd March 2004, 01:00 AM   #3
diyAudio Member
leadbelly's Avatar
Join Date: Dec 2002
Location: Calgary, Alberta
Obviously I cannot be sure without seeing the gauge in front of me, but based on what I have seen, my guess would be that it would be far far less effort to disassemble the gauge, isolate the light bulb socket from the common ground wire, solder on a new wire, and then just hook up the 2 light bulb wires in Subaru-polarity. Usually aftermarket gauges have good access to the lights for replacement purposes.
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. Bertrand Russell
  Reply With Quote
Old 23rd March 2004, 10:40 AM   #4
diyAudio Member
Join Date: Oct 2002
Location: Pennsylvania
Thanks guys. After Thinking about it some more I think you're right, it would be simpler to isolate the lighting and hook it to the Subaru moving ground, and hook the gauge operation wire to a "real" ground on the chassis. I forgot there's more than one way to skin a cat.
  Reply With Quote
Old 23rd March 2004, 11:12 AM   #5
diyAudio Member
Join Date: Oct 2002
Location: Pennsylvania
The master of Microsoft Paint strikes again with a circuit diagram. I'll post pictures when my job is complete.
Attached Images
File Type: gif lightingbeforeandafter.gif (8.3 KB, 82 views)
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
dimming to flourescent Adnancoskun Parts 2 7th February 2009 08:18 AM
Dimming lights skooter Car Audio 12 2nd December 2007 06:10 AM
head unit problem.No output through interior speakers but rca outs work fine spooney Car Audio 2 1st January 2007 11:08 AM

New To Site? Need Help?

All times are GMT. The time now is 01:42 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2