Looking for suitable under-hood fuse tap [for OBA system]

G'day, forum members:

First, yes, I have been searching the forum threads and have not found suitable intel to be helpful on this quest.

Background: I have a 2012 Taco TRD Pro with which I tow a small Airstream. I added Firestone Ride Rite air bags to the rears to assist with hitch porpoising, which works well. Not being able to "tune ride" on the fly for long distances, I recently had a local custom shop install a Firestone Air Command Xtreme Duty onboard air system with the F3 remote. They hosed things up by running the new hose for one of the bags ALONGSIDE the exhaust pipe, which promptly melted. Needless to say I couldn't even fill the bags manually after their "custom" work. [Note: I went back once to the "custom shop" to have them actually fasten the ECU unit TO the truck instead of letting it bounce on the frame rail under the hood loose, as well as to add the airline loops for moisture avoidance which were missed in the clearly written instructions.]

To get things back to a serviceable state I've spent four days under the truck rerouting things, adding a titanium heat sleeve where appropriate, adding bypass T's in the bed cubbies for each side so I can run manual if desired (so not to experience this adverse situation again), and reinstalling the second complete custom mounting plate for the compressor under the hood as they "modified", bent, broke the weld, and stripped out all three fasteners (and none of them were tight) on the first one. [Yes, I had to pay $75 again for the custom-designed steel compressor mounting base, prime and etch again, and merely reorient it with the compressor to fit correctly with appropriate fasteners torqued at an acceptable range.]

Yet, it's this last piece I encountered is what I'm seeking assistance on. The local "custom" shop (incidentally which does custom work nationally!), added the fuse tap under the hood to my fuse panel to the "AC" fuse. This means, it only works when I have the fan on. (They continue to please me, can you tell?) I wish to add an auxiliary fuse box from Painless, but will do so at a future date so I can get back on the road with my Airstream.

Question: If I'm looking for a keyed-on fuse to put the pigtail on, I don't wish to use the EFI as I hear things cycle on even with the truck off, and some of the others are so loaded with componentry I would hate to fail while in motion. I wonder about the Radio 1 fuse for a prospective pigtail for this OBA system to only run with the key on? Can someone confirm if this is an acceptable route to solve?

I'm happy to provide pics of the set up when I am complete, including the custom mount which fits perfectly in the engine bay front of passenger firewall using the three factory bolts for what I believe is for the super charger.

Many thanks!

 

If it were me, this is how I would do it. Mount the relay under the hood and you only have to run 1 wire through the firewall grommet.

 

Cool, thanks for the help and speedy response, but that's not quite dialing it in. Maybe this image will help. I have no "switch" as it's coming from the Firestone ECU. I have everything covered EXCEPT the green circle (which is the fuse box under the hood for accessory pigtail). That's my question, which is the least-restrictive IGN on fuse to tap?

 

OK, so Your box labeled ECU, is that an Electronic Control Unit specifically for turning the compressor on? If so, where does it get it's power from?

 

Yup. It's the magical Firestone black box. Diagram shows, from its relay, coming from the battery with a fused wire. This is the Firestone harness, so I don't have other stuff to figure out other than whether the Radio 1 fuse under the hood could be a likely culprit to power on the whole system with key-on.

 

The radio#1 and radio#2 are both constant battery power. There may be other places under the hood to get key power, but the Acc7.5 fuse in the dash fuse box would be a safe place to put in an add-a-fuse.

 

As I'm planning for an auxiliary fuse block soon for all my accessories [seat heat, defrost mirrors, driving LED's, under-bumper rear floods, and OBA system], maybe I'll just route it there temporarily. Or, perhaps another forum member has an idea for keyed power under the hood other than AC and EFI? Thanks much for the time, @Muddinfun !