I use a 12 V air compressor at my car for air suspension which I understand is draining around 30-35 A. The problem what I have is overheating and eventually burning the pressure switch and connectors.

How can I redesign this to avoid burning pressure switch?

1 Answer 1


The power of your compressor is given by P = V x I = 12 x 30 = 360 W. This sounds about right.

It sounds as though your compressor is badly made and that the pressure switch is not adequate for the job.

You could try to modify like this.


Figure 1. Relay control of compressor motor.

Rewire the unit as shown.

  • Use a 12 V relay rated for > 40 A. Your local car parts shop should have something suitable.
  • When the pressure is low the switch will close and energise the relay.
  • The relay will power the motor.
  • When the pressure is high the pressure switch will open and the relay will turn off. This will turn off the motor.
  • The pressure switch will run cool because there is only the relay coil current passing through it.
  • Use heavy gauge wire for the motor contacts. The relay coil can be light gauge.

enter image description here

Figure 2. 12 V relay found by OP. Terminal numbers used on Figure 1.

  • 3
    I wouldn't be surprised if a starting compressor peaks near 2 times the running current. Might be wiser to get a relay with a make-current > 60A. Break current, of course, can be 40A. Another option is release-sparking. Maybe add in a beefy diode to your schematic to catch that, make it more likely to catch the problem?
    – Asmyldof
    Feb 5, 2016 at 19:18
  • I reckoned the OP might have trouble with the electronics and kept the answer very basic. Would a car parts shop have a suitable alternator diode? I suspect they're all three-phase rectifiers.
    – Transistor
    Feb 5, 2016 at 19:24
  • Thank you for suggestions but…for me are to match information’s about I don’t have any idea. I understand the basics and I know to read the diagrams but nothing more, I know what I want or need but not how to do. I find this relay and I understand how to make the connections amazon.com/Viair-93940-Compressor-Relay-compressor/dp/… For all suggestions please keep them really basic Thank you
    – Edmond Dragut
    Feb 5, 2016 at 19:35
  • See the update. You need to get a few 1/4" (6.35 mm) push-on terminals to attach the wires - like these. Again, your local car shop should have them.
    – Transistor
    Feb 5, 2016 at 19:51
  • I have already 16 gauge wire with automatic fuses for plus and minus directly to the battery and for connecting with pressure switch I solder. I will use the push on terminals for relay Thank you
    – Edmond Dragut
    Feb 5, 2016 at 20:44

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