Constant 12V and Ignition switched 12V sources
 

Guys,

I'm in the process of hooking up a marten repeller system (as my E39 M5 used to have) and I need to find a source of 12V + constant power under the hood, as well as a source of ignition switched 12V + to connect wires to my unit.

I thought about wiring directly to the + post on the battery to get my constant 12V+ but it would look awful to have an extra wire stuck on the positive post terminal (the reason I dont run an amplifier- I hate the idea of the power cable connected to the positive post and running across the engine bay, looks messy to me)

Would the starter motor post be the next best idea? I'd like to keep the engine bay stock and clean looking without wires crossing things and looking out of place.

Obviously it will be weatherproof inline fused correctly and use weatherproof connectors as well. Just unsure of where to tap to find my power sources.
Anyone been here before?

I realize a marten repeller might be a bit alien to people in the US. Think of it as insurance against critters getting under the hood and chewing the wiring up. Google it :)

Assuming the fuse panel looks the same from LHD to RHD models, this is switched power ---> http://i1126.photobucket.com/albums/...ox002mediu.jpg

A underhood constant 12V+ source other than the battery terminal should be easy to find. I would probably tap into the underhood fuse box. A multi meter would be handy.

Thanks Jim, yes the fuse block under the dash is the same RHD to LHD so I used switched 12V+ from that spare spade spot.

For under the hood, I ran the constant 12V+ wire to the starter motor + post using a ring terminal.
I then added a 5A inline fuse (inside a weatherproof inline fuse holder), a few inches down the wire off the post.
Following that is a weatherproof disconnect plug.

Unit itself draws 7W, or 0.4 amps of power to operate. Hopefully the drain will not discharge the battery between the days I use the car. Time will tell I guess.

Seems to work well, emits a very intimidating "ZZIIP, ZZIIP!!" electrical noise, much like an electric fence installation. Its supposed to work between 25000Hz and 58000Hz in the ultrasonic frequency, so lets hope the rats and weasels stay away from my under hood wiring during the winter :)

If your car has or had a power antenna there is a good source of switched 12v right behind the radio.

Where can i tap in near the trunk? (meth pump install)

The power antenna does not work that way. It is not ignition switched.

The antenna only powers on when you change the CD player function from 'CD' to 'Radio'. The player then sends 12V to the antenna.

If you were to hook into the antenna power wire, for say, a boost controller, you would need to change the player to 'Radio' every time you wished to power on the boost controller. Not good.

Best switched power source behind the stereo is the switched power wire which turns the stereo on/off with ignition.


**I had a meat headed flatmate who was hopeless at any and all car related work. He drove a fast & furious-inspired 1994 Toyota corolla hatchback, with Daewoo wheels and blue neons, and burgundy paint. Ugh. Anyways, poor lugnut used to only connect the constant 12V wire to power all of his stereo units in his car and his friends cars and his girlfriends car. And twist all the connections together with his fingers and then wrap it in household masking tape. Managed to continuously drain the batteries on every car he ever put a stereo into, and fried the dash wiring on one.
There are some real idiots out there.... *shakes head*

Have you rewire your fuel pump? I would use the same signal for your meth install, just have it trigger an additional relay.

Hooking up a boost controller, i need a 12v ignition wire and a ground. Since I'm looking for a clean setup, would it be okay to use the wires going to the ecu for this?


Looked around a bit,
ignition source should be connector 1B and ground should be 4C according to this chart:

link to chart

All these months later and I found another very convenient place to tap for constant & switched 12V power.

Removing the upper and lower plastic clamshell halves of the steering column cover, I found an unused factory plug tucked up on the bottom of the ignition/column assembly.

It has 3 spare female spade connections in the plug- red is constant 12V, the other two (blue and something else) are both ignition switched 12V.

My car being a RHD JDM automatic, your US cars may be different in the wire colors, and the plug may be in use. But now I know it is there, tucked away, waiting for the next electronic gadget to use it :p

a pic for the electrically retarded? :)

Maybe its a cruise control plug?

would you guys say its ok to run both my water temp and wideband gauges off this spade source?? or would it be better to find another separate source for the 2nd gauge? thanks

I wonder if this was for the telephone that was optional in JDM models :lol:
I'm going to see if I can use this plug for my homelink/autodimming rear-view mirror

^Added back into thread for reference.