Can this unit be used with a normal electric outlet or do I need to buy an ac/dc convertor when I want to use it in the garage without a battery?

This unit is strictly a 12 volt DC powered compressor. If you wish to use this on house current, you will need to use a 12 volt DC power supply which could handle the required amperage. I would suggest a small car or lawn mower battery of at least 100 ampere capacity. Put a trickle charger on it and you would good to go. Most of these battery powered compressors will draw considerable current during operation and they will get hot so be sure to take care when operating and keep the compressor clear of any combustible items.

What does the “automatic” refer to?

According to a customer Service rep at Viair, the 440P-auto does NOT let the user set a desired pressure and then automatically shut off when the tire reaches that pressure. All it does is shut off when it meets the compressors max rated pressure. Perhaps the service rep did not know what he was talking about, but if that's all it does, the feature is just about useless: If you pump a typical tire up to 150 PSI, you most likely have already damaged the tire.

What is automatic about it? does it shut off a a set psi? i want all my tires at 32

Hello, The automatic feature is not a "set it and forget it" type. You will still have to manually control the pressure for each tire. Our portable compressors with the automatic feature really helps when moving from tire to tire, and when checking tire pressure in the middle of a tire fill. Non automatic compressors must be turned off between tire fills, and anytime you want to check tire pressure. That means you'll be running back and forth to the compressor turning the unit on and off. The automatic feature will save you time & effort to get tires inflated quickly. Thanks, VIAIR Corp 949-585-0011

Must you continuously hold the lever on the inflation gun to inflate a tire? Seems like that would be very tiresome to do anything but add a few lbs.

It doesn’t take that long to fill em. I’d rather hold the chuck in one hand and and a beer in the other than get distracted and forget it. The original filler clip fell off the stem a lot and made it a 2 hand job so I got another one at Home Depot for 20 bucks. I carry regular chucks and lots of other spare parts like valve stems and covers. When I air down I pull the stems right out. When I’m filling I have a small fold up stool to sit on (or my cooler)and a digital gauge. I always have extra valve covers too. Most of the stuff Fits in a pill bottle. I carry an extra 25’ hose in case. Happy trails.

Voltage	12 Volts
Recommended Uses For Product	Tire Inflation
Power Source	Air Powered
Noise Level	74 Decibels
Special Feature	Automatic Shut-Off, Portable
Item Weight	10.7 Pounds
Capacity	2.3 Cubic Feet
Style	Portable
Model Name	40045
Manufacturer	Viair
UPC	818114004056
Global Trade Identification Number	00818114004056
Product Dimensions	27.61 x 14.81 x 19 cm; 4.85 kg
Item model number	40045
Manufacturer Part Number	40045
OEM Part Number	40045
Assembly Required	No
Special Features	Automatic Shut-Off, Portable
Item Weight	4 kg 850 g

VIAIR 400P-Automatic Function Portable Compressor

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Common Questions