I'm in the process of installing an airlift compressor system in my truck and was wondering if anyone had any good ideas of where to grab ignition power behind the dash without going.through the firewall to the fuse box.

Thanks guys,
Mike

 

Grab it off the switched cigarette lighter.

 

Mike,
if you use the cigarette lighter to power it up, make sure the electrical load required to run the air compressor dosent exceed what the cigarette lighter fuse is rated for. If the cigarette lighter fuse isnt rated for the load that the air compressor requires, you`ll just blow the fuse... and also, putting in a bigger fuse in the cig/lighter circut is a great BIG huge no no. Your better off finding an empty "switched" fuse slot out under the hood, that would be MUCH safer too. Also, unless you`re mounting that compressor inside the truck cab, you`ll have to run wires, hose`s into the cab to hook it up regardless.

 

Cigar fuse and line are rated at 20A. I have all my radio accesories tied off of that line. They all add up to 14A and I haven't had any issue's BUT you cannot use a Tap and then use the outlet for something usch a a cab mounted light(plw light) or similar. You must account far all things used by that line.

For something such as an aircompressor, I would honestly think about running a line directly to the battery. Aircompresors have a spike on start-up(high inrush current) and this might be an issue.
A compressor rated at 10A may spike close to 30A on start-up. DC inrush current is very high(~300% of actual rated current)

Most circuits are built to withstand brief spike, but with Dodge and thier electronicsally controled fuses(TIPMs), I would think twice about! Short out a circuit on a TIPM and it'll cost several hundred dollars to replace what used to be a $10 relay 10years ago.

 

Well the reason I didn't want to go to the battery is because I'm looking for power only with the key on. The setup I bought uses a low air pressure switch to keep 5 psi in the bags at all times. I'd be worried about the compressor kicking on at various times with the truck off and killing the battery. As for the tipm, I'm scared to go tapping into there lol. What happened to the days of spare power slots in the fuse box??? Anyway, I tapped into the power wire for the cigarette lighter. I never run anything else off of it with the exception of my cell phone charger, which uses very little amperage. Also, I bought the standard compressor, as opposed to the heavy duty one. Reminds me of one of those cheap compressors you plug into your lighter socket to fill your tires.

 

Use the cigarette receptacle as a switch, through a relay, and run the power from the battery. It's much easier than it sounds.... the cigarette power triggers the relay to pass current. It's simple.

If the compressor is rated below the fused socket, it should also be fine.

As insurance, run an inline fuse, smaller than the lighter socket fuse, and it will blow before the receptacle reaches capacity.

 

Even at low 5psi, there's the initial inrush current. For even 1/4watt compressor, the inrush is very high. Well past 20A the circuit is rated for. I've used it for a portable compressor, but those are generally 1/8th watt and are rarely even used. BUT, they are still spiking higher than what the circuit is fused at. Constant cycling on/off will burn out your contacts within that circuit!!! It's something you cannot see but does happen.
I never said to tap into the TIPM directly, but in reality all wires come from there, so any wire you touch is tipm controlled!

I'm with WNDRER on this one.

I'll help you out some.
Get a 4-pin Auto relay rated for 30/40A
Pin 30 goes to fused battery(12v+)
Pin 87 goes to your compressor power
Pin 85 goes to ground
Pin 86 goes to switched Cig lighter 12v


Even using factory wiring(T-tapping), you should still run an inline fuse between your compresor and the circuit you tap to atleast have some isolation. And it should be a fuse rated slightly les than the circuit itself. So, 15A in your case.