How to Install an Onboard Air Compressor on Your Tow Rig

Have you checked your tire pressure lately?

85 percent of all tire air pressure losses are the result of slow leaks that occur over a period of hours, days, or months. NHTSA

The Project

I’m also guilty of not checking tire pressure as often as I should. As I started thinking transitioning to an RV-based lifestyle I had nasty visions of attempting to finagle the truck and trailer combination into gas stations to check the tire pressure.  I’d rather not do that.

I had already put an on-board air compressor on the Jeep I used to own. I knew that decent-quality 12v pumps were now available for under $100. I set out to outfit our tow vehicle with a similar setup.

In this post I’ll show what it took to install a 12V onboard air compressor on our 2002 Chevy Silverado 2500 with the 8.1L gas engine.

Hardmount or Portable?

You could just carry the 12V compressor in a bag and get it all out when you needed it.

I wanted a more permanent installation that would make it easier and quicker to use.

I envisioned:

  • The pump mounted away under the hood
  • A dash-mounted switch to turn it on
  • An exterior-mounted air connection to hook an air hose to

Do you lose portability this way? I don’t think so - I can either just string a long hose or move the truck close to where the pump is needed.

Steps Involved

Overall the process requires the following steps:

  • Sourcing the Air Compressor
  • Adapting the Air Compressor
  • Mounting the Air Compressor
  • Wiring up the Air Compressor
  • Plumbing an air outlet in the truck bumper
  • Creating an inflation tool

Sourcing the Air Compressor

I started with a Q Industries MV50 SuperFlow High-Volume 12-Volt Air Compressor purchased from Amazon.

These pumps have been around for a couple of years and are well-liked by the off-road community where tire pressure changes are frequent. 

Price?

The unit is reasonably priced at $60 - $80 and is easily adapted for different situations. 

Faults?

They have some faults but the fixes are well-documented in these discussion forum threads.

Adapting the Compressor

Our Chevy truck had a nice large open spot under the hood so I adapted the unit for permanent mount by:

  • Removing the handle.
  • Removing the gauge and plugging the hole left behind.
  • Removing the rubber feet to enable those spots to be used for screws.
  • Modifying the wiring to bypass the included switch (I siliconed it over hoping to keep the wiring out of the elements).
  • Inspecting the connections to the compressor’s relay and fixing one cold solder connection.
  • Changed the wiring so the positive side would be switched instead of the negative (so the load would light up an illuminated dash switch).

Air Outlet

The last step was figuring out what to do for an air outlet. 

The threads on the compressors main outlet are non-standard, so I couldn’t easily remove the male fitting and hard-connect an airline. 

I settled for this arrangement - a quick connect coupled to a tee, with a adjustable pressure-relief valve on one output and the other outlet used to connect the air line:

Let it Bleed

This is a tankless air compressor designed to always pump air.

This is not how normal residential or industrial air compressors work. Normal compressors only move air when an airtool is running or you are inflating a tire.

When that isn’t happening, the air pressure “backs up” to fill a tank. Once the tank is full there is both a switch mechanism to turn off the pump and a safety release valve that pops before the tank explodes.

By changing this compressor to use standard air hoses and fittings it needed a way to bleed off excess pressure. That’s what the adjustable pressure-relief valve does. Of all my tires my road bike tires needed the highest PSI at 90 - so I set the valve to begin to bleed at just over 90 PSI.

Mounting the Compressor

The compressor fit into the target spot almost like it was designed to fit there.  It nestles under the fender support, and one of the mounting holes actually lined up with a hole already in the fender:

The pump is narrow enough to allow room for the hood spring when the hood is closed:

I was only able to get 3 feet mounted, as the front inner one ended up directly under the hood/fender support.  I used both double lockwashers and Loc-tite on the 3 feet I did mount, so I’m hoping that works well enough.

Wiring the Air Compressor

Wiring up the air compressor is really two jobs - the dash side and the underhood side.

Truck Dash Wiring

The truck’s original stereo had both a CD/FM headunit with a remote cassette deck mounted further down in the console.  The headunit has been replaced with an aftermarket version which left the cassette deck inoperable. 

I removed the cassette deck, and used its mount to create a switch panel big enough for two switches with paired-up fuses (the 2nd set for auxiliary back up lights):

The switch panel slides into place like the original cassette deck did - making wiring an easy chore:

Once in place it ended up looking good:

Underhood Wiring

From there I sourced power under the truck’s hood (the ‘02 Chevy has a remote jumper cable connection point that worked well) and ran the loom across the firewall:

In my box of spare 12v parts I found a distribution block big enough to handle the 12v power, the trigger power from the dash switches (that connect to relays), and the ground connections for both the air compressor and auxiliary lights:

Plumbing an Air Outlet in the Truck Bumper


Once the pump was mounted I ran flexible rubber air line down the truck’s frame to the rear bumper.  I drilled a hole through next to the license place for the air outlet - figuring this spot would be usually half-way between truck and trailer tires.  It’ll also be handy for airing up bike tires.

I had to use some washers to space out the connection for a good seal.  I bought stainless washers so they won’t rust.

The Inflation Tool

This is a leftover from my Jeeping days - an inflation tool consisting of a plumbing valve, to a three-way manifold, to a pressure gauge and then to a “whip-hose” (which has an flexible end), to a clip-on chuck:

5 Comments How to Install an Onboard Air Compressor on Your Tow Rig

  1. Picture of Kairi Gainsborough Kairi Gainsborough March 14, 2016

    I never thought about installing an air compressor on a truck before. This seems like such a smart idea, because you would never have to worry about low tire pressure. I wonder if this can be done on any type of vehicle, or does it have to be a big tow truck?

  2. Picture of Boyink Boyink March 14, 2016

    The only constraint is the available space - the compressor doesn’t care if it’s mounted to a truck or a Yugo. :)

    Many off-roaders have similar setups in their Jeeps, Broncos, blazers or Four Runners. They air down to go off road for better traction. This lets them air back up when they hit pavement.

  3. Picture of Kairi Gainsborough Kairi Gainsborough March 15, 2016

    That’s a good point. I’m definitely going to have to look into doing this myself! Thanks for your reply!

  4. Picture of jason Lee jason Lee April 30, 2016

    My good buddy has a compressor set up in his super off road jeep. He is always going deep in the mountains. I go with him often and i can tell you we have used that dang compressor more than you would think. I recommend hooking one up regardless of where you drive. I finally put one on my f150 and have used it many times already to help stranded folks out.

  5. Picture of Bry Carter Bry Carter June 18, 2016

    Great job.  Looks very handy. To answer your question, I prefer the mobility of my portable unit for airing up tires/things.  The problem I ran into was power cord length to reach my RV tires so I installed marine grade 12v cigarette outlets near the tires on my RV (both sides).  It was simple to permanently connect them to the RV battery and if I ever upgrade my compressor or have to borrow one I am ready to plug it in.

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