HornBlasters Digital Air Pressure Gauge

The digital air pressure gauge can be used to monitor the air pressure within your tank from the cab of the vehicle. Now onto the installation process.


The HornBlasters Digital Air Gauge is designed to fit in a 2" hole. The gauge itself has a 2 1/16th" diameter. If you have a gauge pod already set up for a 2" gauge, you may skip straight to the plumbing section below.

If not, we will need to make a mounting spot for this gauge. The easiest way to do this is with a hole saw. Milwaukee makes a great hole saw with a 2" diameter. Check it out here. Once you have found a suitable location for your gauge, use the hole saw with a drill/driver to create a 2" hole for our gauge. You can sand down the edges of the hole to make it flush/smooth, and move forward with the install process.


The digital gauge comes with a sending unit that plumbs into the tank, as well as the gauge itself. The sending unit has a plug on the top that will accept the wiring harness for the gauge face.

Air Pressure Sensor

The sending unit for the gauge has PTFE paste pre-applied for your convenience. We don't recommend using Teflon on this unit as bits and pieces of the tape can find it's way into the sending unit and may cause it to read inaccurately. This piece will be inserted into the tank with the help of a reducer bushing. If you are working with a 5-gallon tank, you will need a 1/2" NPT x 1/8" NPT reducer bushing. For 2-gallon tanks, a 1/4" NPT x 1/8" NPT reducer is necessary. Ensure that this sending unit is not overtightened, the recommended torque spec is 12 ~ 14 ft/lbs.

Start by threading the reducer bushing into your tank. You can use any port other than the bottom-most port on the tank. Once the reducer has been threaded into the tank, slowly thread the gauge sending unit into the reducer bushing. The image below shows the sending unit threaded into both size reducers.

Properly Installed Air Pressure Sensor

If your reducer bushing does not have red PTFE paste pre-applied, go ahead and wrap the male thread with Teflon tape. 3-4 clean wraps around the thread is ideal. If you do too many, there's a chance that air can leak from in between the wraps of Teflon.


Thankfully, this gauge is not that difficult to wire up. Let's start with harness #1. This harness has a plug that can be inserted into the sending unit threaded into the tank.

Air Pressure Sensor Wiring Harness

Harness #1 has three wires. A green, brown, and black colored wire. These wires will be routed up towards the actual gauge itself, and will connect to harness #2. Go ahead and plug harness 1 into the sending unit, and begin routing the wiring harness up to the front of the vehicle.

Now, grab harness #2 and go up to the gauge itself.

Digital Air Gauge Wiring Harness

Harness #2 can be plugged into the back of the gauge face. Take the excess wire from this harness and put it through the hole you created for our gauge. Route the plug from the inside of the hole and connect it to the gauge face. Leave the gauge out of the hole for now, for easy access.

At this point, the leads from harness #1 & harness #2 will need to meet somewhere in between the tank and the gauge. It is up to you as to where you would like to join these wires together.

Harness 2 has six leads that come off of it. The Black wires can be joined together and MUST be grounded with the black wire that comes off the sending unit. You will want all three black wires to ground together at one point.

The yellow lead on this harness will route up to the battery Positive terminal. Alternatively, you could connect this lead to the output side of our fuse holder, to prevent any damage in the event a short is created.

The red lead on this harness will connect to a key-power-on source, similar to the pressure switch that came with your kit. You can connect this lead to the same circuit as the pressure switch key-power-on wire if you desire. Otherwise, this wire must be connected to any circuit that is only on when the key is on, to prevent the gauge from draining your battery overnight.

Before you connect the green/brown wires together, route the green/brown wires from one harness through the supplied vinyl wire insulation. This is the small black plastic tube that came with the gauge.

Go ahead and connect the green/brown wires together and slide the tubing over the exposed wire leads.

Finishing up

Now that the gauge has been wired up, you can move on to the last portion of the installation. Take a look at the back of the gauge itself. Above the wiring harness/plug is a small cover. You can remove this cover to gain access to two small switches.
PSI/BAR Switch

Switch #1 (left) allows you to change whether or not the gauge displays in BAR or PSI.

Switch #2 (right) allows you to change whether or not the gauge displays the battery voltage after turning the vehicle on. You can change these however you would like. We recommend keeping switch 1 in the 'ON' (up) position so that the gauge displays PSI. BAR is another method of measuring pressure and 150 PSI is equal to 10.3421 BAR. If your gauge is only reading 10 PSI when full, it is likely reading BAR instead. Switch #2 is completely optional, as it will not change the way our gauge reads the pressure in the tank and controls whether it shows the vehicles battery voltage when it comes on or not.

Once your switches are set up the way you want, go ahead and mount the gauge into the hole you created during Step #1.

Mounting the Gauge

The gauge comes with a small set of mounting hardware.

Digital Air Pressure Gauge Mounting Hardware

Start by taking the two bolts on the left, and thread the female end of each onto the studs located on the back of the gauge.
Mounting Hardware Installed

The end result will look like the image above. At this point, seat the gauge within the hole you made earlier. Ensure that it is oriented the way you want.

Once the gauge has been seated into the hole, locate the plastic sleeve that came with the gauge. This sleeve will inserted over the gauge from the back, as shown in the image below.
Installed Digital Air Gauge

The flat side of this sleeve will go onto the gauge first, and will go up to the mounting surface you used for the gauge. At this point, take the small L-bracket and position it so that the ends stick towards the front of the gauge. Line up the holes with the two studs on the back of the gauge and press the bracket in place. Place one washer on each stud over the bracket, and secure the bracket tight with the two supplied nuts. The finished product should look like this from the back.
Back of Digital Air Pressure Gauge

The bracket will sandwich the gauge and the sleeve to the mounting surface you are using for the gauge. Ensure that both nuts are tight and secure once mounted.

At this point, your digital gauge has been installed and is now ready for use.