Originally Posted by jaykay (Post 638621)

Thank you, yes I am aware of that plug. Its very handy but I think the circuit is only rated at 7.5 amps. I am no electrician but I would think connecting up two 5amp loads would give trouble on that circuit.

Inside the cockpit, I am considering pulling power off of a rarely use 30 amp circuit and then have individual 5 amp fuses for each load .....and others.

I was eyeing the defroster fuse which is 30 mps and should provide switched 12v to power a number of different loads. I believe one would stick a tester on to one fuse terminal with ignition on and that will do it. Then plug in a fuse tap and run that to your terminal block to power all of your stuff. I am not sure what would be a good available ground for the terminal block near the fuse box.

I never use the defroster but I guess there could be trouble if one accidentally hit the defrost button. Is there a better 30, 35 amp circuit out the fuse box that would be better?

The are unused slots but I doubt there is power there. I really need to get a good tester.

Originally Posted by pilot4fn (Post 638629)

Sounds like you need quite a lot of power there.
Why not use a relay between. Take a the switched power from some easy spot to wake up the relay and the actual power to your 5 + 5 Amps directly from battery thru that relay?

Originally Posted by jaykay (Post 638881)

Well I have a number of loads. Which easy spot do you recommend?

Originally Posted by jaykay (Post 638880)

Yes, at present I am separated from a FSM (full service manual) access, but I do recall difficulty in using it to determine which leads are switched 12v. To an electrical neanderthal like myself this is pretty much a needle in a haystack but I will give it a go.

#1 power a number of loads in the cockpit via a terminal block. IIRC the block can handle 35 amps coming in:
-shift light;
-l and r fan switch latching relays; Press the AC button, it will turn on the fans. Also finding a 30 amp latching relay is very difficult and not cheap when you do find one.
-engine compartment fan latching relay; Why? DME is going to turn this on when it wants to
-ipad charge; get this and wire to radio switched/ground https://www.amazon.com/gp/product/B08K271H6W
-foot well lighting; Use LED's and wire into existing wires
-machine guns; Thinking a 100amp will be the minimum here, more if you want an ejection seat
-camera;
-phone charge; Plug into the same above. also another one you could hide somewhere https://www.amazon.com/gp/product/B072JC1DQF
-secret stuff; Can't help with this since it is a secret
-engine gauges. These usually dont require power unless they are lighted, which would just wire into existing interior lights such as at the radio.

I would think the 7.5 amp phone connector powering the terminal block would not work. The fuse would certainly pop as the draw from two of the above loads would kill it. Hence, the original question: how to best safely tap a 30 amp circuit from the footwell fuse box.....phew. And ground it....properly.

#2 Power an engine gauge sensor module to be located on the trunk firewall with ignition switched 12V power. The load is fused at 5 amps. Sensor wires will be routed through the trunk firewall somewhere. I think the engine bay itself will be too harsh for it.....

Originally Posted by Stl-986 (Post 638989)

I dont see any issues with mounting the device in the trunk, it does make sense. Requiring power to come FROM the trunk though is what makes no sense to me. Other then it just taking some time it's really not a big deal. That is how the wiring got there to begin with. What is there already has a purpose and it is sized accordingly.


I am trying to avoid running wire from front to back if it is not needed. I dont often have much time to work on these things. The module and sensors appear to require the same ground location in order for them to work. Less complication in the trunk.

It really should take only a couple of hours to run a wire to the distribution panel up front and wire into the ignition circuit. You can put the relay in the trunk but you need to get power that really on it's own and not fused with something else.

Yes, I absolutely hate wiring and it would take me a lot longer than 2 hours. I am not electrically inclined enough to confidently splice into the ignition circuit. I have an idea but if there is procedure out there let me know

Not to say this will happen with this specific device but imagine you tap into a circuit that is also used by something such as the DME. The device you add draws more then the connected fuse and the fuse blows. You have now also shut off the computer and the car because of it. This is why when adding aftermarket items it is always best to go straight off the 12v source, use a relay, it's own inline fuse and if necessary trigger with ignition.

Very much agreed; hence the original post

Keep in mind that most circuits have a fuse that is 10% or to the nearest size up of the devices connected. For example if a radio uses 12amp a 15amp fuse will be sized as will the wiring for 15amp. If lights will use 25amps it will be sized for 30 amps, etc. Rule of thumb is to add 10% of the load and go to the next size up.

Originally Posted by ike84 (Post 638973)

I recently ran wiring for a boost controller and wbo2 from the rear trunk to the cockpit. It's not at all hard to do. You sound rather convinced that you have to find a tpower supply in the trunk but let me know if you change your mind and I'll let you know where I ran my wires.

Thanks for this. I am interested in your route. See the comments above regarding wiring hatred and common ground

Stl is right - you have to take a lot of things into consideration when planning new circuits, unless the amp draw is minimal.

Agreed. The load to be introduced is what it is though.

The easiest thing to do is (for small sensors) run them up to the phone jack in the center console.

Agreed but in this case the module will cover all sensors and it will draw 5 amps out the 7.5 available on the phone jack leaving not much for other loads.

For larger loads, use that switched current for a signal line to a relay which is run directly off the battery. Again, not difficult to do - I just ran 8ga wire from battery to engine firewall tonight in under 2 hrs (and that was with completely dismantling the shift console and running it under the carpet the whole way.

Impressive, I would be interested in your route. from the battery to the first firewall? The tricky part is from there to the trunk. I have 18 gauge in place under the console dedicated to other things at present. 8 sounds good for that long length and more current. Yes, I was really trying to stay away from console removal again...just finished some shifter bearings. Maybe use 16s as a puller...

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Originally Posted by ike84 (Post 639000)

There is a grommet behind the battery that goes through the front firewall. That's the way from the frunk into the cockpit. From there run it back along the center console, tucked under the carpet, or along the door sill, whichever you prefer. From there go under the carpet on top of the engine bay cover. At the very rear bulkhead, you will find that the holes along the top communicate with the trunk. Just fish the wire through and voila.

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Originally Posted by Starter986 (Post 639235)

In the trunk. The relay box driver side. Slot/spot #10. I've switched power running a couple wires out of where the relay sits. I don't recall into where the two wires run. My mechanic brought to my attention that's where I'm missing the relay for the SAIS.

Power comes on when ignition is turned on. Shuts off power about 15 seconds after the key is removed.

Originally Posted by Stl-986 (Post 639277)

Help Me DIY did a good video on installing seat heaters. It includes getting access to the wiring in the door sill. Take a look at it. Not all that difficult to do. Can be done with the seat in the car, but much easier with it out, which only takes a few more minutes.

Originally Posted by jaykay (Post 639671)

Any chance you can post an image of this relay? Then I might be able figure out what is on that circuit and permissible current draw.

Originally Posted by jaykay (Post 639673)

Thanks I will look it up. Was this the grommet you used or was it the big body plug right behind the battery? I try and get bigger pictures…..it is a real weird item.