dome light, dvd problems

This is a lengthy post. I just wanted to provide all the detail as possible.  Please note I am not an expert, but I know my way around. 

I have run into a problem with this installation and it seems to be related to the Acadia’s power discharge avoidance system.  (where your dome/reading light will go off after 10 minutes if you leave it on with the ignition off).

PROBLEM: Mysterious Power draw develops 10 minutes after doors closed ONLY if overhead DVD is connected.  However – it does not drain through the DVD.   Let me explain, maybe someone can help.

There are 3 wires in my dome light cable that I have feeding my overhead DVD:

Orange : +12V constant power

Note:   ALL EXAMPLES have the ignition off.

Problem scenarios:

A)  ---WITH NO WIRES HOOKED UP----

At the 10 minute mark, there is a small click in the dash area and the voltage on the orange wire drops to about 11.5V, but the battery still reads full voltage with virtually no draw on the battery.

B)  ---WITH Orange wire hooked to DVD positive and Black wire hooked to DVD negative ---

At the 10 minute mark, the orange wire drops to about 9.5 volts and immediately the battery voltage begins to drop (.1 V every 1 minute or so) ALTHOUGH the draw though the DVD is still .012A.  CONCLUSION – there is power being dumped somehow elsewhere in the system due to the small load of this DVD (.012A)

OTHER NOTES/SYMPTOMS:

1)      TEST 1 - In B – If I click on another dome light/reading light (or even open the door) AFTER the 10 minutes, the voltage on the ORANGE wire jumps back (from 9.5V) to normal battery voltage and the battery voltage slowly recovers from it dropping rate.  However, if the dome light is clicked off or the door is closed the problem returns in 10 minutes.

2)      TEST 2 - In B – If I also turn on a dome light at the beginning (or at least BEFORE this 10 minute threshold), it will go out at the 10 min mark. HOWEVER – this time the orange wire goes to ZERO volts as the dome light has tripped the relay on this circuit to prevent the battery being drawn down (like it should). Why doesn't it doe this with only the DVD drawing power.

What is the deal???   The only thing I can GUESS is that since the DVD player’s standby draw is so low (.012A) compared to a dome light that the relay does not trip out as usual and the dome light circuit itself goes into some kind of standby with slightly reduced voltage – but what's up with the leak that starts only then.  I just don’t get it.

I know I could go find power somewhere else to avoid this circuit, but that might be tough with airbags in every pillar.    There has to be a workaround or at least an explanation!

As it is, the only way I could avoid the draw on my battery when the ignition is of is to intentionally turn on a dome light every time I exit the car!  (so that this circuit gets shut down).   

Any help or suggestions?

Definitely get your +12v constant elsewhere.  Best scenario: the battery.  I've run into this problem and other similar problems when I first started installing overhead's in GM vehicles.  The first three GM SUV's gave me nothing but headaches until my supervisor slapped my head and told me, "don't be lazy and get the +12v constant at a proper location."  Many years ago, and ever since I've never run into this problem.

In most later model GM SUV's the +12v constant is fed by the BCM.  By no means a high-current output device.

Save yourself a headache and run a new +12v constant.

Thank you for the slap on my head. What a screwed up circuit that dome light is.

Works like a charm now.

Based on GM bulletin: 1868070

Subject:  Diagnostic information on “Parasitic Battery Draw” with possible “No Start” condition – BCM (Body Control Module) power timer.

Models:

2006 – 07 Buick Lucerne

2006 – 07 Cadillac DTS

2006 – 07 Chevrolet Impala, Monte Carlo

2007 Cadillac Escalade, Escalade ESV, Escalade EXT, SRX

2007 Chevrolet Avalanche, Equinox, Tahoe, Silverado, Suburban

2007 GMC Sierra, Yukon, Yukon XL, Denali, Denali XL

2007 Pontiac Torrent  

When performing a diagnosis on a battery that has gone dead overnight, an installer may notice that the vehicle has approximately 4.1 amp draw on the system. The draw may be steady or may drop to a few millivolts then go back up to 4.1 amps. 

This may happen if you install an overhead monitor or other accessory and connect to the orange constant positive power wire in the vehicle’s courtesy light circuit. This will cause the power timer in the BCM to keep re-starting. The BCM will awake and draw 4.1 amps. 

This orange wire circuit exists the BCM at pin 1 of connector 2. Cut the wire to test this condition.  

Feed your aftermarket accessory in a different fashion.