# Burning air pressure switch

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?

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

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.

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

• 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? 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. 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. 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