Passing wiring through firewall

Any of the accessory power wires will be fine to power the relay. Not sure about the new Hilux's but I used to just poke a feed wire down between and existing loom and the grommet and then pull it through or, i would actually drill a hole to suit the wiring, put my own grommet in and then use that. That was on a '90 model Hilux

Usually there are rubber bungs somewhere in the engine bay firewall that will allow you to get the wiring through.
I would strongly suggest that you supply power to the pump via a relay.
Run the relay earth to a switch in the cab and from the switch to a convenient ground.
Run a heavy wire through an inline fuse to the relay then from the relay to the pump.

There are many ways of doing this plus some relays come with the wiring diagram.
If you are not sure ask an auto sparky. To find a firewall entry you could also ask a smash shop where you can get an entry point.
Some others here may also know a good entry point for the wires.

In my '98 'lux I have run wires up through the floor via drain hole grommet. Punched a mall hole in the grommet, run the wires down and sealed with silicone. As above, run through a relay and fuse as close to the battery as possible.

Cheers

HI newlux - Not sure about the new 05 model but most firewalls will have a blank plug for accessories you may fit later in the vehicles life --- so you may have to search a little -

as for wire - whats the amperage rating for the compressor ? if you choose any accessory wire from under your dash you might choose a wire that will not be up to the load - and as a result will either burnt out your compressor OR melt the wire/ or even both -- best bet would be to go off the battery if its a high demand item

Frank

Absolutely must wire it from the battery. That model compressor has a high power draw and will melt any substandard wiring which could burn the vehicle to the ground (it's happened before). Also it will not run as well as it could if it cant get enough juice.

New, (can I call you that?) it all depends on whether your firewall is a hardware or software firewall, hardware firewalls are easy, just run the wire directly from the battery and use necessary grommets and other protection for the wiring as it passes thru the firewall casing, also one thru the firewall make sure you have a fusebox, and a fusable link at the other end (the battery end).

If its a software firewall then you have all sorts of worrysome problems as the technology to digitise copper wiring is really only in its infancy and is still at this stage limited to 1.0mm cable. you'll need at least 6.0mm. even when the technology catches up, digitised cable is only good for 50% of its current carrying capacity as when it in de-digitised, it changes its molecular structure to something approximating titanium, a much harder and more expensive element.

Of course I havent mentioned the noddles, they are the plastic bits you plac in series between the battery/fuse/fusible link continuum

Mrs Al knows about Noddles. Dont ask about Doddles.

Newlux,
Pushing or pulling a cable through a rubber firewall grommet can be a challenge. If you insert the empty body of a Bic biro through the grommet, the cable can then be fed through the inside of the body and the pen body is then simply pulled off the cable on the inside of the cab. Same theory as creating an emergency airway down someone's larynx.
Regards
Jon W