Saturday, February 12, 2022

Installing an On-Board Air Compressor (Maxi Trac)

Finding the right RV compressor can be challenging, especially if you want one that can inflate RV tires to a high pressure. Many RVers highly recommend the Viair RV compressor. Off-roaders and overlanders choose the ARB CKMTA12 On-Board Twin High Performance Air Compressor because it is a quick and dependable inflator, but it is pricey.

I'm looking for a low-cost, high-output, high-pressure compressor capable of quickly inflating RV tires, air mattresses, and inflatable toys (kayaks, SUPs, and so on). Our 120-volt portable compressor inflates one SUP in about 20 minutes, which is excruciatingly slow. The Napa Maxi-Trac air inflator is getting a lot of buzz in the DIY community, so I took the plunge and ordered one. With a 20% OFF coupon, it cost me slightly more than $100.

The Maxi-Trac has a large single motor with 2-huge piston compressors on both ends, specs state it draws around 90-amps at 12-volts and with advertised output of 300 LPM. I’ve seen YouTube videos comparing it to the more expensive On-Board ARB Twin Motor inflator ($600) and the Maxi-Trac airs up the same flat tire about 2x to 3x faster than the ARB, granted it not same quality as an ARB so its longevity is questionable.

The Maxi-Trac has built quality issues, soldered wire connections could be better, the accessories/air hose/gauge are cheap quality. The air hose connection uses Japanese style quick connectors and not compatible with NA automotive or industrial quick connectors, but for the price, I can buy 6 Maxi-Tracs vs. one ARB Twin Motor.

The Maxi Trac is advertised with air pressure cut-off, but mine kept running with the air hose closed off and that could be bad for the compressors. It has a logic circuit board which appears to be a power cut off circuit based on amp draw but it is not doing anything, possibly the cut-off threshold is set too high.

The incoming (+) 12-volt wire is wired straight into the motor which also feeds a temperature switch (not visible) then a small gauge wire from the temp switch into the power switch. The (-) 12-volt wire terminates into the board and is being switched ON/OFF via 2 high amp relay connected in parallel. Turning the power switch ON energizes the 2- high amp relay which in turn powers the compressor motor.

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First mod is to secure the (+) wire butt splice connection as there are bare wire strands poking out the heat shrink wrap which could short out into chassis ground. I applied generous amount of silicone caulk into the circuit board for water proofing. The air output connection was removed and replaced with a 1/8” to 1/4" Male to Female NPT adapter then to a short 1/4" brass nipple then to a 4-way air manifold. An air pressure switch (On-90-psi/ Off- 120-psi) to one port of the manifold, a 150-psi over-pressure valve to another, and a universal female air quick connector to the remaining port.

I decided to fabricate a compressor mount that attaches to the rear end of the receiver hitch. There is enough space behind the hitch and under the van for the compressor and I can easily slide it out the hitch receiver if I needed to. I use an Anderson quick connector (175-amp version) for the 12-volt connection and a removable remote key switch for powering the inflator. All 3- connections to the inflator (air output hose/ power switch/12 -volt power connection) uses quick disconnects for ease of removal and servicing in the future.

FYI: It is not necessary to permanently mount the Maxi Trac compressor, but it is an option. The compressor comes with a lengthy power cable with battery clamps and is ready to use right out of the box. A 25-foot rubber air hose with a gauge is also included.

Rear view of the mount after painting flat black

Front view

With the inflator bolted into the carrier

The front and rear side of the carrier were covered with Coroplast. The Coroplast covers were secured into the carrier using automotive plastic rivet fasteners.

Anderson style power connectors

With the inflator mounted towards the rear of the hitch receiver. A few inches of space is needed between the top of the compressor and the undercarriage to prevent hitting the adjacent cross-member during compressor installation or removal. Noticed the hitch tightener installed to prevent the carrier from vibrating/moving while underway.

(+) DC connection was tapped from the generator (+) 12-volt junction post then an inline 90-amp auto reset breaker was used before the Anderson quick connector.

Picture showing the ground wire connection to the chassis. The area was sanded down to bare metal then the wire lug was bolted into the frame. A spray of black paint over to prevent any corrosion/rust from developing. 

Remote inflator power key switch and air hose quick connector. The air connector rubber plug was salvaged from an old natural gas quick connector cover (needs modification to fit the air hose connector).

Key switch and air connector mounted behind the rear bumper metal frame.

Fabricated an acrylic end cover for the key switch and air hose quick connect mount. I painted it red to make the compressor a tad quicker, lol :-).

Looking from behind the van and you would not notice that there is something hanging behind the hitch receiver.

Optional Accessories:

A modified Inflatable SUP Pump Schrader Air Valve Adapter. For better airflow, the Schrader valve was removed and replaced with a 1/4" NPT ball valve and a male air fitting quick connect.

The Maxi Trac compressor is a beast, it inflated my SUP to 13-psi in 3 minutes and 7 seconds. It is currently the quickest SUP inflation by a portable compressor on YouTube (drop me a comment if you find something quicker 😃). Video proof below.

I updated the SUP air compressor adaptor by adding an analog pressure gauge to it for quickly double-checking the SUP air pressure. It also provides pressure comparison between the digital tire inflator for greater accuracy during inflation.


  1. Hi, thanks for this post. Great ideas here. Looking to do something similar on my Ford Transit DIY camper. Just wondering how things are holding up so far with the compressor mounted underneath the chassis? Have you found any issues with moisture/water corrosion or electronics problems? Thanks!

    1. Hello and thank you for stopping by. I've been using it a lot to inflate our SUPs. It's been running perfectly, with no moisture or water issues, but we live in sunny/dry southern California.

  2. Hi, I ran a similar setup cable for mine with the Anderson plugs, and a 90 amp breaker. Each time I try to run it seems the power is not enough and I just hear a click and doesn't run. I'm using batter gauge wire for the setup.

    1. Your battery may be weak and dropping voltage, or you may have some bad connections causing a large voltage drop; check the wire connectors for solid crimps. Also, try running the engine to help your batteries and see if that doesn't trip the breaker. When the voltage is low, the compressor motor can draw more current and trip the breaker. Mine does not draw nearly 90 amps, but rather 68-70 amps at 12.5 volts.


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