ACC (ignition switched) power source near 1998 LS400 headliner?

[onedadinseattle]

I have a dashcam that's supposed to use an ACC (switched) 12V signal to distinguish between when the car is parked and when it's in use.  But the shop that installed it hooked it up to an always-on source instead.  Thus, the dashcam doesn't switch into parking mode.  It keeps recording and eventually drains the battery.

The wires disappear into the headliner, so it's possible they connected it to a power source for the dome lights or sunroof.  I'll either rewire it myself or take it back to the installer.

Is there a source of switched power in the headliner that I could use instead?

[paulo57509]

On 4/10/2022 at 11:01 AM, onedadinseattle said:

I have a dashcam that's supposed to use an ACC (switched) 12V signal to distinguish between when the car is parked and when it's in use.  But the shop that installed it hooked it up to an always-on source instead.  Thus, the dashcam doesn't switch into parking mode.  It keeps recording and eventually drains the battery.

The wires disappear into the headliner, so it's possible they connected it to a power source for the dome lights or sunroof.  I'll either rewire it myself or take it back to the installer.

Is there a source of switched power in the headliner that I could use instead?

I took a quick glance at the interior lighting schematic and it appears every interior lighting or motor circuit is constant +12v, switched by the body ECU.

You most likely need to find a circuit that is at the ignition switch.  Attached is the 1998 Power Source wiring schematic.  I'd look for a circuit that is controlled by the ignition switch; find the switch and work outwards.  Unfortunately, this makes for a lot of wire routing.

I would take the car back to the installer.

[onedadinseattle]

@paulo57509, cool that you also have a 1998.  After looking at the alternatives we've decided to keep ours as long as possible.

I did not find an attachment to your post.  Is there another source for this schematic?

[Bykfixer]

Would it be practical to install an on/off switch on (or near) the dash-cam itself? 

[RX400h]

I've installed switched parts like tachometer, digital clock, laser jammer, etc. I found the switched power wire with a DC voltage tester like the one shown in the link. It was always near the ignition switch.

Katzco Voltage Continuity and Current Tester - 6-12 V DC - 24 V AC Circuit - Heavy Duty - Long Probe Tester With Indicator Light - 54 Inch Cord for Low Voltage Systems, Cars, Live Wires, Fuses - - Amazon.com

[paulo57509]

8 hours ago, onedadinseattle said:

@paulo57509, cool that you also have a 1998.  After looking at the alternatives we've decided to keep ours as long as possible.

I did not find an attachment to your post.  Is there another source for this schematic?

Relevant schematics are attached.  These are directly from Toyota Information Services for the 1998 LS400 model year.  Use with discretion.

Personally, I'd avoid tapping into a circuit attached to the Multiplex Comm System.  It's most likely safer to tap into a switched circuit at the ignition switch as suggested elsewhere.  Simply because this is way upstream of any vehicle control ECU's.  You'll find the ignition switch in the 66 - Power Source attachment.

66 - Power Source.pdf 163 - Multiplex Communication System (Communication Bus).pdf 165 - Multiplex Communication System.pdf

[onedadinseattle]

54 minutes ago, paulo57509 said:

Personally, I'd avoid tapping into a circuit attached to the Multiplex Comm System.  It's most likely safer to tap into a switched circuit at the ignition switch as suggested elsewhere.  Simply because this is way upstream of any vehicle control ECU's.  You'll find the ignition switch in the 66 - Power Source attachment.

I appreciate the help.  I didn't even realize there was a Multiplex Communications System!  My other car is a 1970 VW.

From the diagram I see that the fuses for the front cigarette lighter and "RADIO NO. 2" (why are there two?) are both after the ignition switch and might be good candidates.  Hopefully these are the little fuses in the footwell and maybe the installer will be able to install a fuse tap rather than alter the car too much more?