ATTN Elec gurus -- ILLUM(-) questions..

Dendrobium · 03-10-2005, 04:48 PM

In an 02/03 bug-eye IMPREZA,

Seems that it is common knowledge that the ILLUM(+) wire is "switched",
but I did a search and couldn't find any info on the corresponding ILLUM(-) wire?

My questions are:
1. Is the ILLUM(-) wire also switched? ie. what does it normally sit at when the car is OFF. Does it ground itself? connect to +12V, or does it go open-circuit? (I'm thinking open circuit since the ILLUM- must be controlled by a dimming circuit that receives switched power?)

2. For those who have done LED conversions -- do you get FULL range of dimmability? ie. what range does ILLUM(-) sweep -- is it small enough so that "most" LED's (ie. 2-3V) are able to remain functional even at full dim? or does ILLUM(-) eventually decrease the voltage so much that your LED's shut off completely?

I tried searching but all I found was info on the funky Subaru reverse-dimming setup (which I understand) - but I couldn't find exact answers to the above. Any help would be appreciated. Much thanks

-- Dendrobium

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brunetmj · 03-11-2005, 11:43 AM

Although I don't know the answer directly , it could easily be tested. Just put a meter on the wires on the hazard warning switch. It has both the violet and orange wires associated with the illumination system.

Dendrobium · 03-11-2005, 12:41 PM

thanks,
I tested it last night, I found that ILLUM(-) sits at ground when the dash lights are off, then goes to your dimmer-selected variable voltage when the dash lights are turned on.
-- so it is not a "switched" output that is normally open-circuit.

Uncle Scotty · 03-11-2005, 05:14 PM

All 'NEW" Subaru's are a 'switched( - ) '

...and if you are trying to wire gauge lights, the spare plug on the radio harness is 'dimmed' with the panel lights...

Dendrobium · 03-11-2005, 06:19 PM

Hmm... sorry if my question was confusing -- I was actually looking for an in-cabin "switched ground" analogous to the ACC which is a "switched positive".

I am hooking up an EcuTek Dash display -- alarm output -- which uses the 12V OBDII port output as power (which stays at a constant +12V, even when the car is powered off -- but not necessarily on some MY's IIRC).

The reason I wanted a "switched ground" is so that I could use it to light some indicators/circuitry only when the car is on, but to turn off after the car is shut off (key removed from ignition). Without a "switched ground", the lighting/circuitry will remain on becuase it has a constant +12V feed from the OBDII port.

The ILLUM(-) is not ideal as it varies from 2V-11V to "reverse-dim" the dash lighting, but it was the closest I could think to a "switched ground". Unfortunately, it goes to ground rather than open-circuit when the car is shut off, so it doesn't suit my purposes.

Uncle Scotty · 03-11-2005, 06:31 PM

PM sent....

03-10-2005, 04:48 PM	#1
Dendrobium Scooby Specialist Member#: 24234 Join Date: Sep 2002 Chapter/Region: VIC Location: Canada Vehicle: 2003 WRX Wagon 5sp WRB	ATTN Elec gurus -- ILLUM(-) questions.. In an 02/03 bug-eye IMPREZA, Seems that it is common knowledge that the ILLUM(+) wire is "switched", but I did a search and couldn't find any info on the corresponding ILLUM(-) wire? My questions are: 1. Is the ILLUM(-) wire also switched? ie. what does it normally sit at when the car is OFF. Does it ground itself? connect to +12V, or does it go open-circuit? (I'm thinking open circuit since the ILLUM- must be controlled by a dimming circuit that receives switched power?) 2. For those who have done LED conversions -- do you get FULL range of dimmability? ie. what range does ILLUM(-) sweep -- is it small enough so that "most" LED's (ie. 2-3V) are able to remain functional even at full dim? or does ILLUM(-) eventually decrease the voltage so much that your LED's shut off completely? I tried searching but all I found was info on the funky Subaru reverse-dimming setup (which I understand) - but I couldn't find exact answers to the above. Any help would be appreciated. Much thanks -- Dendrobium * Registered users of the site do not see these ads.

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03-11-2005, 11:43 AM	#2
brunetmj Scooby Specialist Member#: 8023 Join Date: Jul 2001 Location: Way-upstate , NY Vehicle: 2019 Crosstrek white	Although I don't know the answer directly , it could easily be tested. Just put a meter on the wires on the hazard warning switch. It has both the violet and orange wires associated with the illumination system.

03-11-2005, 12:41 PM	#3
Dendrobium Scooby Specialist Member#: 24234 Join Date: Sep 2002 Chapter/Region: VIC Location: Canada Vehicle: 2003 WRX Wagon 5sp WRB	thanks, I tested it last night, I found that ILLUM(-) sits at ground when the dash lights are off, then goes to your dimmer-selected variable voltage when the dash lights are turned on. -- so it is not a "switched" output that is normally open-circuit.

03-11-2005, 05:14 PM	#4
Uncle Scotty * Banned * Member#: 16200 Join Date: Mar 2002 Vehicle: OK buy Nates beans westcoastroasting.com	All 'NEW" Subaru's are a 'switched( - ) ' ...and if you are trying to wire gauge lights, the spare plug on the radio harness is 'dimmed' with the panel lights...

03-11-2005, 06:19 PM	#5
Dendrobium Scooby Specialist Member#: 24234 Join Date: Sep 2002 Chapter/Region: VIC Location: Canada Vehicle: 2003 WRX Wagon 5sp WRB	Hmm... sorry if my question was confusing -- I was actually looking for an in-cabin "switched ground" analogous to the ACC which is a "switched positive". I am hooking up an EcuTek Dash display -- alarm output -- which uses the 12V OBDII port output as power (which stays at a constant +12V, even when the car is powered off -- but not necessarily on some MY's IIRC). The reason I wanted a "switched ground" is so that I could use it to light some indicators/circuitry only when the car is on, but to turn off after the car is shut off (key removed from ignition). Without a "switched ground", the lighting/circuitry will remain on becuase it has a constant +12V feed from the OBDII port. The ILLUM(-) is not ideal as it varies from 2V-11V to "reverse-dim" the dash lighting, but it was the closest I could think to a "switched ground". Unfortunately, it goes to ground rather than open-circuit when the car is shut off, so it doesn't suit my purposes.

03-11-2005, 06:31 PM	#6
Uncle Scotty * Banned * Member#: 16200 Join Date: Mar 2002 Vehicle: OK buy Nates beans westcoastroasting.com	PM sent....