Viair 450C Air Compressor Kit with 40 Amp Relay - Continuous Duty

In this review the Viair 450C Air Compressor Kit with the 93940 40 Amp relay is evaluated as a practical solution for users who need a reliable 12 volt source of compressed air on vehicles and equipment. The bottom line: this kit is best for operators who require a true 100 percent duty cycle compressor that can run continuously with the engine on, and who value a compact, easy to install package that includes a heavy-duty relay for safe electrical control.

Key Features

• Continuous duty design: The 450C delivers a 100 percent duty cycle at 100 PSI and 72 degree ambient, so it can operate for extended periods without needing cool-down breaks.
• Strong free flow: It produces 1.66 CFM at 0 PSI and 0.94 CFM at 100 PSI, giving usable air output for inflating, actuating small air tools, and operating valves without a tank.
• High working pressure: The compressor reaches up to 150 PSI max working pressure for applications that demand higher line pressure.
• Included stainless braided leader hose: A 1/4 NPT stainless steel braided leader hose with inline check valve streamlines hookup and prevents backflow into the unit.
• Relay for safe electrical control: The 93940 40 amp relay with four 1/4 in spade posts and mounting tabs handles up to 40 A and is supplied so each compressor can have proper relay control.

Who It's For

This kit is aimed at farmers, contractors, and off-road vehicle owners who need a compact, durable compressor that can run while the engine is on and maintain pressure through extended use. It is suited for applications like inflating tires, operating small pneumatic systems on planters or trailers, and powering small air tools when a tank is not required.

Those who need very high CFM for continuous heavy-duty pneumatic tools or who require an onboard air tank for long tool cycles should consider a larger compressor or add a separate tank, since this model is optimized for continuous but modest CFM output without a reservoir.

Pros & Cons

Pros

• Reliable 100 percent duty cycle performance at rated conditions for extended runs.
• Good portability and easy installation with the included stainless braided leader hose and insulated wiring.
• The 40 amp relay simplifies safe, proper electrical installation and protects the compressor wiring.
• High maximum working pressure of 150 PSI covers a range of tasks.

Cons

• Noise reports are mixed; some users find it noticeably loud when running without a tank.
• CFM is modest compared with larger shop compressors, so a separate tank may be needed for high-demand tool use.

Specifications

Our Verdict

The Viair 450C kit with the 40 amp relay is a sensible choice for anyone who needs a compact, continuously capable 12 volt compressor that installs cleanly and runs reliably with the engine on. It offers good value for duties that require sustained pressure rather than high CFM bursts, and the included relay and braided hose make proper installation straightforward.

Frequently Asked Questions

Can the compressor run continuously?
Yes, the 450C is rated for a 100 percent duty cycle at 100 PSI and 72 degree ambient when the vehicle engine is running.

Is the relay necessary?
Yes, each compressor should have its own relay for proper electrical control; the kit includes the 93940 40 amp relay with four 1/4 in spade posts.

Will this unit power air tools without a tank?
It can power light pneumatic tasks and actuators, but for extended tool use a separate tank is recommended due to modest CFM at working pressure.