Tapping Power From Factory Rearview

[vcoglian]

Has anyone has attempted to supply power to their radar dectectors from by tapping into the power leads to the factory auto dimming rearview mirror? I was planning on powering my Passport 8500 from it, but was unsure if that circut has enough juice.

 

[rando]

I haven't tried it because I don't have the mirror.

Assuming you have the factory mirror and not one that was added at the port or by your dealer (these may be wired differently) then your mirror power (yellow lead) is on the 15 amp circuit protected by the IG1 fuse. Below is the complete list of systems on that circuit. Some of these systems also draw power from other circuits. So when something like the headlights are on this circuit, it could be the headlight relay versus the actual lamps themselves.

Air Conditioning
Automatic Glare-Resistant EC Mirror with Compass
Back-Up Light
Charging
Cruise Control
Door Lock Control
Electric Tension Reducer
Electroncially Controlled Transmission and A/T Indicator
Headlight
MultiMode 4WD
Multiplex Communication System
Navigation System, Radio and Player(w/ Nav), Toyota Parking Assist (Rear View Mirror)
Power Outlet (115V)
Rear Window Defogger and Mirror Heater
Seat Belt Warning
Seat Heater
Stop Light
Taillight and Illumination
Trailer Towing
Turn Signal and Hazard Warning Light
VSC


The only way to know how much headroom you have is to pull the fuse and put a current meter in series with the circuit. Turn on everything (and try lots of combinations) and see what the peek current draw is.

 

[vcoglian]

Thanks! I've got the direct wire kit on order from Escort. I'd think with the 115v outlet (which to this point I've never used) on that circut, that the measly couple of mva that the detector pulls shouldn't do much harm. I'll make sure I get photo's of the install in case any one else is interested in doing similar.

How would one know if their mirror was added at the factory or at the doc?.

 

[rando]

So let's be careful here. If you read what I posted, I mentioned that just because a system draws power from a circuit doesn't mean it doesn't draw power from elsewhere. The 115V system only uses the circuit in question to power a relay coil (i.e. low current draw). The primary power source for the actual 115v inverter is on its own 15A circuit. So the fact that you don't have or don't use the 115v system doesn't imply that there is massive headroom for adding devices. Again, the only safe way is to test with a current meter.

According to the wiring manual, the factory mirror has two wires. A yellow 12v and white with black stripe ground wire. These wires are part of the roof wire harness which runs along the top of the windshield, down the driver side pillar, and into the driver side junction box.

If you remove the fuse cover on the lower dash you can see the junction box. The mirror wires terminate into the 20 pin connector, 1A. facing the panel from the front, find the top right connector. It should be in a vertical orientation with the pins as shown here.

20 10
19 09
18 08
17 07
xx xx
16 06
15 05
14 04
13 03
12 02
11 01

Pin 02 should have the yellow 12v wire attached to it.
Pin 14 should have the white with black stripe wire.

If you don't have these wires in these locations then your mirror was probably wired up outside the factory. In that case, I cannot say which circuit it's on.

 

[bryancos]

Why not just tap it off the accessory fuse located under the lower left dash (remove the plastic door -- look at the label to locate the access. fuse) There's also a ground bolt located at the bottom left of the dash... this is where I supplied power to the aftermarket oem autodimming mirror and my compass...

 

[rando]

Regardless of which circuit he taps, he still needs to make sure there is power to spare. Most likely his radar detector doesn't draw much current and many circuits would suffice.

Why not just check with a meter to be sure?

 

[vcoglian]

Thanks for all the ideas.

I'm a bit hesitant to pull off the A pillar and route cables through there because of the side curtain airbags. Since there's already power up there, I'd just sooner grab power from the mirror or map lights.

 

[rando]

If you do decide to pull a new feed from the fuse box, you can get down there without disturbing your curtain airbag. The airbag runs along the top pillar above the front and rear doors. The wiring you'd need would run down the pillar along the front windshield ... away from the airbag.

My guess is that your safe to just use whatever is powering your mirror. But for my sanity, I'd just pull whatever fuse that currently protects your mirror circuit and test it with meter and all accessories on to see if you have the current to spare. You should be able to do this in less time than it will take you to type another response.

Good luck!