Radar detector hard wire power
 

I'm looking to hardwire my radar detector and pull power that is switched on by the ignition. Been searching around and trying to get a definitive answer as to what wire to easily tap from the head unit behind the dash. At first I thought it was a red wire that's ignition switched on and then someone with a 1991 said their wires were switched and it was the red/black wire that's ignition powered.

I've tried looking at the workshop manual electrical schematics (attached to this thread), but I'm not too sure what the numbers (2.5, 1.0) actually mean. I'm a beginner when it comes to wiring.

The numbers on the schematic refer to the size of the wire in mm^2.
2.5 mm^2 wire is ~AWG 14, 0.75 m^2 wire is ~AWG 18, etc.

More importantly, if you have the continental radio then there should be two plugs (three if you count the antenna connection) on the back of it.
The large black plug should have a red wire which is switched 12v+ (ignition) and a yellow wire which is constant 12v+ (battery)
Tapping the red wire will give you switched power for your radar detector, but the radar detector may cause interference with your radio.
If this happens, you can try smoothing the interference with a ferrite bead or power filter, or you can tap a different source (e.g. cigarette lighter, seat motor power, etc.)

I do have the Continental radio...good advice about interference though, as I'd like to do it right the first time (wishful thinking for me though).
Seat motor power seems like a better option so I can just pop out the switch on the side of the seat, tap the red wire, then I can run the power wire up the side for the radar detector.

You don't want to tap the seat from where the adjustment switches are; you want to tap where the seat motors get power from the floor of the car (big rectangular plastic connectors).
Can't remember 100% if this is switched or constant power, but it's easy to check if the seats will adjust with the car off!

Seats are constant power.

Assume you are installing the detector by the rear vision mirror. I just ran the wire behind the moulding rubber. Undetectable. When you get to the bottom corner there is a hole that you can feed the wire into the frunk and then into the fuse box from an access hole. I used a piggyback fuse holder to get the power. I can't recall which source I used for the power. But the detector comes on with the ignition.

Pretty much exactly how I installed mine. I can't recall which source I used neither.

I like the idea of pulling it into the fuse box. When I did mine, I tapped into the radio. Fires up with ignition only. But in retrospect, pulling it through the firewall and into the fusebox may have been easier.

I pulled mine through the firewall to the fusebox using a previously clipped wire and there is a ground point in the passenger footwell (if I remember) correctly. I did have to run the wire around the dash at one point and tucked it behind the little triangle fascia. Running the wire up and around the gasket was simple...but here's a tip...try to start it with the wire in place and run it from the detector back down...you don't want to be bunching up an extra bit of wires up there.

Do you have any radio interference with when the radar detector goes off?

Good advice to start from the radar detector and back down.


Anyone know what fuse you can piggy back off of? Or if an empty fuse has switched power?

For all the cars I have I hardwired a 12v feed lead for the detector (which draws less than 2A in my case - Snooper). Located a 10A unused/empty or not applicable switched fuse slot and gave it its own piggy back fused tail (w/ 10A fuse). Added long enough 20A cables that were butt soldered / heat shrinked. All nice and tidy. You have the choice to keep the 12V extension socket attached that the detector is plugged in to or cut this off and wire in full length cable to the detector jack plug (which is what I did). The extra expense of course is buying a few extra sets of the detector power leads.

I'm going to test any empty fuse slots this weekend to see which, if any, are switched power. My radar detector (V1) doesn't draw much power either.

If I make it by my warehouse I'll take a photo of where/how I landed my wires in the fuse box.

There are usually split opinions about piggy-backing off an existing used fuse slot (you only have to youtube it) - some say no harm at all and others the complete opposite. You could argue that a low draw detector would be fine, and it probably would be. However, for some that piggy back in an additional 12v accessories socket for detector use you can never be 100% certain it wouldn't be used for something else - e.g. plugging in a tyre inflator would definitely load up that circuit. Just makes safety sense and provides peace of mind to use a 'gifted' empty switched slot.