First install... Wiring question.

Hey guys,

I’m installing my new system this week and I wanted to ask you guys your thoughts on the best way to wire it. I am running a Viair 444c with 2 two gallon tanks. I am using a 4 pole relay/solenoid from viair. Here is my question… I was planning on running my trigger wire for the compressor from the fuse box, to a toggle, and down to the pressure switch and then to the relay. However, I have read some threads about voltage spikes surging the system if a diode isnt used. After reading this I thought about just running a hot wire from the battery to a switch and down to the pressure switch for the trigger. But then I’m worried about toggle switches being constantly being burned out without a relay between the battery and the switch on the trigger wire. What do you guys recommend? This is a brand new truck so I’m wary about voltage spikes and frying my electronics.


Why not just run one 5 gallon tank.

I am limited with space. 2 two gallon tanks fit without modification.

If you’re running the Shockers, more than 2 gallons isn’t needed.

I’d recommend you look at the installs section here on the forums, wiring schematics are all over the place and in high rez diagrams.

Voltage should remain stable, but your amps/watts will bounce up and down a bit. As long as you have a good alternator you’ll be fine.


I’m running a nathan K3LA. The main reason for 2 of the tanks is that I’m also using this for air tools. I have read many of the posts and studied the diagrams but my only concern is the voltage spike from the relay up the trigger wire when the electromagnetic field collapses inside the relay. Some report up to a 400v spike for a fraction of a second. I know most people arent concerned with this but I’ve read alot of posts where people recommend a diode and alternative wiring. I’m just wondering what would be best.

Where’s your trigger coming from? You only need to consider the V spike if you’re coming from an ECU or similar. If you’re coming from the likes of a cigarette lighter socket for example, you wouldn’t worry about it. If you have concerns, just go get a simple diode (e.g. 400V 1A) and place it inline to your trigger (i.e. parallel to the coil of the relay). There’s also relays available that have in-built diode protection.