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.

The check valve is the piece circled in red above. You can use two wrenches to remove it from the compressors' braided line. Once seperated, you want to try and blow backward through it.

The check valve has an arrow on the side that indicates the direction of flow. You ant to blow AGAINST the arrow and see if you can blow air through the check valve backwards. You should only be able to blow in the direction of flow and not backwards through it. If you can blow air through it both ways, then the check valve is bad.

Exposed Power Wire

An exposed power wire can cause the fuse to blow. If your red power wire has copper leads that are frayed or exposed at the ends, these leads can touch the metal frame of the vehicle and create a short to the battery. This will cause the fuse to pop instantaneously when it is seated into the fuse holder. If this happens, you need to follow the red wire all the way back to the pressure switch and ensure each crimp connector is properly crimped onto the wire, and ensure that no copper leads are frayed or exposed at your connections. In some cases, we have seen where the wire is too close to an exhaust manifold and melts. This can lead to a short as well if the wire makes contact with the manifold itself.

Poor Connections

Poor connections from the fuse holder to the pressure switch can lead to a popped fuse also. If your crimped connections are loose and making poor contact with the copper wire, this can lead to a drop in voltage and an increase in amp draw. Your compressor pulls a good amount of power and poor connections will hinder it from getting the power it needs to operate properly. Poor voltage can lead to decreased performance and the motor burning out fairly quickly.

Wire Too Long

If your run of wire from the battery back to the pressure switch/compressor is too long, you will lose voltage due to the length of the wire. If you plan to run longer than 20' for your main power wire, we recommend increasing the size of the wire to 8 or 6 gauge. A larger gauge wire will allow you to run a longer distance of wire without losing voltage.

Worn out Carbon Brush Assembly

If you can't fix this problem with the solutions above, your compressor may have a worn out set of carbon brushes. The carbon brushes are responsible for the transfer of power from the red/black wires to the motor. Over time, these brushes can wear similar to those found in electrical power tools. HornBlasters offers carbon brush rebuild kits here. Carbon brushes can cause the motor to run poorly, or not at all if they are worn and on the verge of failure.


In the event that the above solutions are of no help, opening a warranty claim would be your next best bet.