Where do I connect the dimmer wire (c-5) ??
Melting Slicks
Joined: Sep 2000
Posts: 2,756
Likes: 5
From: Satellite Beach, FL, USA
Re: Where do I connect the dimmer wire (c-5) ?? (RichM)
The BCM controlls the dash lights. In the case of the Bose HU, it sends a illumination control message to the HU over the DLC data bus.
The BCM controls other dash lights by Pulse Width Modulating, PWM, the bulbs. The bulb "hot" lead is connected to 12 volts and the BCM is connected to the bulb "return". The BCM pulses the bulb "return" to ground. A wide pulse to ground brightens the bulb and a narrow pulse to ground dims the bub. You need to connect your new HU illumination input to a BCM bulb output and see if your HU likes it. Some do, some don't.
The BCM controls other dash lights by Pulse Width Modulating, PWM, the bulbs. The bulb "hot" lead is connected to 12 volts and the BCM is connected to the bulb "return". The BCM pulses the bulb "return" to ground. A wide pulse to ground brightens the bulb and a narrow pulse to ground dims the bub. You need to connect your new HU illumination input to a BCM bulb output and see if your HU likes it. Some do, some don't.
Instructor
Joined: Jun 2000
Posts: 106
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From: Littleton, Co, USA
Re: Where do I connect the dimmer wire (99HT)
Is there a convenient place to get a bulb output while the console is pulled?
I have a Kenwood (KDC-X859) on the way - anyone tried to connect the dimmer on a Kenwood?
Update: Perhaps it's not as bad as I thought.....
I believe the Kenwood hooks into your illumination lead (not the dimmer lead). If I'm reading this correctly, it just needs 12v when I want it to dim.
Could I then tap the hot lead off the active handling light while I have the console out (or perhaps something around the climate control - or is that all sealed)?
[Modified by David_Levin, 11:21 PM 6/5/2002]
I have a Kenwood (KDC-X859) on the way - anyone tried to connect the dimmer on a Kenwood?
Update: Perhaps it's not as bad as I thought.....
I believe the Kenwood hooks into your illumination lead (not the dimmer lead). If I'm reading this correctly, it just needs 12v when I want it to dim.
Could I then tap the hot lead off the active handling light while I have the console out (or perhaps something around the climate control - or is that all sealed)?
[Modified by David_Levin, 11:21 PM 6/5/2002]
Melting Slicks
Joined: Sep 2000
Posts: 2,756
Likes: 5
From: Satellite Beach, FL, USA
Re: Where do I connect the dimmer wire (David_Levin)
Some have tapped the AC display illumination bulbs for their signal. Just be careful doing it. It may or may not work on your HU.
Instructor
Joined: Jun 2000
Posts: 106
Likes: 0
From: Littleton, Co, USA
Re: Where do I connect the dimmer wire (99HT)
Thanks,
I don't think that will work since my HU is looking for a 12v trigger to dim the display.
(been trying to decipher the schematics in the service manual)
Looks like I can't grab the 12v from the trac cntrl switch lighting either because is full time hot with the BCM mucking with the ground to control the bulb (like you said -> bizarre).
[Modified by David_Levin, 1:25 PM 6/6/2002]
I don't think that will work since my HU is looking for a 12v trigger to dim the display.
(been trying to decipher the schematics in the service manual)
Looks like I can't grab the 12v from the trac cntrl switch lighting either because is full time hot with the BCM mucking with the ground to control the bulb (like you said -> bizarre).
[Modified by David_Levin, 1:25 PM 6/6/2002]
Melting Slicks
Joined: Mar 2001
Posts: 2,671
Likes: 850
From: New Jersey
Re: Where do I connect the dimmer wire (David_Levin)
For auto tranny C5s, you can get the "correct phased" (PWMed 12V) from the shift indicator illumination bulb. For some reason that the only "normal phase" dimmed illumination signal in the C5. It is accesable at the BCM, from where it is generated, but I forgot which connector # / pin #. This signal should be compatable with aftermarket head units, as they expect a variable 12V versus a fixed ground.
Instructor
Joined: Jun 2000
Posts: 106
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From: Littleton, Co, USA
Re: Where do I connect the dimmer wire (ersatz928)
The Kenwood doesn't look for a dimmer - just 12v to indicate the lights are on (I think less then 12v eg dimmer would work too).
Kenwood thought it would need a resistor in the line to work. In any case, I went to the twilight sentinel relay (relay 44) and tapped the leg on the output side (upper left leg - on for either twilight sent or manual switch). This relay provides power for both the headlights and generates a control for the headlight doors.
(remember this will only work for a head unit looking for a lighting as opposed to dimmer circuit)
I wrapped the wire around the leg of the relay up against the plastic and held it with conductive epoxy. I figured if I screwed it up, I could just get a new relay (which for me does nothing since twilight sent it not turned on).
The headlight fuse is big (15 or 20A), so I added a .75 amp fuse to the wire.
[Modified by David_Levin, 10:10 PM 6/14/2002]
Kenwood thought it would need a resistor in the line to work. In any case, I went to the twilight sentinel relay (relay 44) and tapped the leg on the output side (upper left leg - on for either twilight sent or manual switch). This relay provides power for both the headlights and generates a control for the headlight doors.
(remember this will only work for a head unit looking for a lighting as opposed to dimmer circuit)
I wrapped the wire around the leg of the relay up against the plastic and held it with conductive epoxy. I figured if I screwed it up, I could just get a new relay (which for me does nothing since twilight sent it not turned on).
The headlight fuse is big (15 or 20A), so I added a .75 amp fuse to the wire.
[Modified by David_Levin, 10:10 PM 6/14/2002]
