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Viair Compressor Install

A quality, high output compressor is a great addition to any expedition vehicle, as it provides several benefits:

1. Air up tires after a day on the trail at low air pressure
2. Air up a tire with a slow leak, or one that has been plugged
3. Re-seat a bead on the rim (usually requires a reserve tank)
4. Operate ARB Air Locker differentials
5. Blow-off dusty gear, vehicle interior, tent, etc.
6. Operate air tools, grinders and vacuums
7. Provide a positive pressure source for water tanks, etc.
8. Suspension systems requiring air pressure (air shocks, overload air bags, etc.)
9. and a few more...


1. Viair 400C (VIA-400C) compressor
Duty cycle- 33%
cfm- 2.54 @ 0 psi
"four 33" x 12.5" tires from 15 to 30 PSI in about 8 minutes"
2. ARB heavy duty pressure switch (85psi on - 105psi off)
3. Bosch Relay ( Bosch #0 332 209 150 ) SPDT 30A
4. 12v SPST Switch
5. Custom bracket
6. Goodyear air hose (1/4")
7. Misc. brass fittings

I installed the compressor in my 1998 Isuzu Trooper. The most challenging decision, is where to mount the compressor, to ensure the best performance, accessibility and troubleshooting. After considerable discussion, I chose the passenger side firewall, within the engine compartment. There is an unused bracket, and several fender mounted captive nuts that make for a solid mounting location.
The first, and most complicated of the tasks was to fabricate a mounting bracket, as there is not a "flat", solid location available in the engine bay. I used 1/16" plate steel, cut on the band saw. This mount required several bends and angles to accommodate the available mounting holes. This process took about 2 hours between the measurements and fabrication.

I needed to install a SPST switch in-line with the ARB pressure switch, as I wanted the choice of a "demand" or "off" configuration. When the SPST switch is in the ON position, it sends ignition on voltage to the pressure switch. If the SPST switch is in the OFF position, the compressor will not run, regardless of the air pressure in the system. I will likely leave the switch in the ON position, as the system does not currently have any leaks that would cause the compressor to cycle often.
This is a picture of the SPST switch and SPDT relay installed on the bracket. The 12v engine on power comes from the fuel pump circuit to the SPST switch, which is in series with the pressure switch, to the relay (signal position 86)
This is a picture of the pressure switch installed on the compressor. The pressure switch controls the power to the compressor, and the maximum and minimum pressure that the compressor will maintain. 85psi min. 105psi max.
This is a picture of the compressor and components mounted to the base. All connections are soldered, crimped, shrink sleeved and split loomed for reliability.
Here are some pictures of the compressor mounted in the Trooper. Note the remote filter against the firewall. I used 1/4" I. D. Goodyear hose to run from the compressor to the front bumper, where I mounted a standard air chuck.
Impressions This is a very solid mount and a good compressor with excellent output for the size. I tested the compressor on my Isuzu's 285/75 R16 tires (33x11.5") and it filled one from 15 psi to 40 psi in 2 minutes 40 seconds.