Air Compressor wiring

LiftMore

LiftMore

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I'm wiring up switches for future air lockers and not sure if I should tap into ignition or an always hot circuit. Do compressors pull a lot of juice from to battery or can I run it with engine off with no problems? I figure front/rear lockers should definitely be to ignition circuit.

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LiftMore said:
I'm wiring up switches for future air lockers and not sure if I should tap into ignition or an always hot circuit. Do compressors pull a lot of juice from to battery or can I run it with engine off with no problems? I figure front/rear lockers should definitely be to ignition circuit.
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12v compressors typically pull up to 30 amps on start up and 20-25 amps running. Although you do not necessarily have to run your engine while the compressor is on, you can run down your battery if it is not in top shape. Also, most compressors are rated at 13.8 volts which means that you won't get full airflow unless the engine is running at slightly over idle so that the alternator produces the higher voltage.

You should definitely use a relay and not run full power through your switch. Be sure the relay is rated for constant duty. My preference is for a constant duty solenoid rather than a relay.

Whether the trigger for the relay is constant hot or ignition hot only is up to you. I typically use a constant hot trigger because there are occasions when I want a small amount of air and don't want to run the engine, such as when my jeep is parked in the garage, the keys are upstairs, and a neighborhood kid needs his bicycle tires filled.

Here is a simple schematic used by Currie Enterprises when it was marketing 12v onboard air systems in the 1990's. The basic principles haven't changed.
 
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Awesome! I think you convinced me to connect it so it's available without ignition being on. At least it makes noise so I shouldn't have an issue with leaving it on by accident. I've had that happen more than once with spot lights since I drive to work before the sun comes up and get there once it's up so I don't notice them being on. I fixed that when I re-wired these switches :D
 
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