I had wanted to build an on-board air compressor/tank system for my truck. Typical uses would be to fill up bike tires, trailer tires, and occasional vehicle tire when camping, or driving off road. Retail kit systems are over priced, under built, and not the right configuration for my space constraints. I decided to build my own system, piecing it together from new and used parts.
I started with a used, non working, 3gal 110V air compressor that I found on CraigsList for $20. This had everything I needed; like a pressure relief valve, pressure switch, drain valve, check valve, and was the right shape configuration I was looking for. (long and skinny)
I stripped the dead motor and compressor head from the tank, and prepared to mate a 12V DC compressor motor to the tank. This 12V DC motor is from Harbor Freight Tools. It is their HD 150PSI unit, which I modified to hard mount to the tank, and plumb its air outlet to the tank.
I reconfigured the pressure switch to trigger the motor to turn off at 110psi (formerly +125psi) This is to reduce load on the compressor motor and keep it from overheating, and hopefully decrease its failure rate. I also completly removed the pressure regulator.
Once the 12V DC compressor was mounted and attached to the tank. I mounted the whole assembly to the truck bed. The tank has integrated rubber feet, which I used as part of the attach points. Now the tank is semi 'rubber mounted' to the truck bed.
I ran a fused 12AWG wire pair directly from the battery to the compressor. But I also ran another pair of wires from the cab, to the compressor to be used as remote ON/OFF from inside the cab. The remote switch powers an automotive style relay, which allows the current to the DC motor of the compressor. See the full electrical and air line schematic below. The schematic shows additional equipment that supports air horns, but I do not cover them in this instructable.
Remote pressure gauge, and Compressor ON indicator LED.