What is the fuse for?
All of our kits use an inline fuse between the positive battery terminal and the compressor/pressure switch. A fuse is used as a safety feature, in the event that a component should fail, the fuse will pop and break the connection from the battery to our components. Wiring our compressor/pressure switch to the battery is a safety hazard and we would never recommend installing our products without an inline fuse.
The fuse pops when the compressor pulls too much power from the battery. Most air compressors are rated to draw ~18-30 Amps of current @ 13.8 volts(12-Volt systems when the alternator is spinning is at 13.8 Volts). The fuses provided in our kits is rated for 35 Amps. That way for any reason if the air compressor starts to pull more than 35 amps, the fuse will pop in which cutting all power to the system.
Why does this matter?
If the compressor starts to pull more power than the wire can handle, the increased power draw will generate heat and the wire may eventually melt, or even catch on fire. The fuse itself prevents this from happening by "popping" when the compressor pulls more current than it is rated for.
So why is the compressor pulling too much power?
This could be caused by a number of reasons. Let's review some of the common causes we have seen in the past.
Worn Check Valve
The Check Valve on your compressor keeps air in the tank from escaping back out to the compressor. When this piece begins to wear/fail, air from the tank pushes back on the compressor creating resistance. When the compressor goes to restart and re-fill the tank, the pressure exerted on the compressor from the tank causes the motor to pull a lot of power to compensate for this. This in turn leads to a blown fuse. (This is likely the culprit if your compressor fills up just fine from empty, and pops the fuse upon restart).
The check valve can be tested a few ways. The easiest method is to remove it fromm the compressors' leader hose and check for back-flow.