Q-89 Dual Cylinder Compressor


The compressor comes with a nice storage bag.  The hose and adapters fit in the front pocket.  Price was $161.99 delivered.  I bought mine at 4 Wheel Parts on sale.

Oooh, shiny.

The ad claims 50% less time to fill tires versus the MV50 model.

On/off switch with circuit breaker.

This is no cigarette lighter type compressor.  This beast weighs 16 lbs, and can draw up to 45 Amps.

I didn't even bother to unwrap the power cord.  It's plenty long enough to reach as is.

With the truck in the driveway, I was easily able to reach the back wall of my garage with the included airline.  There's was still plenty of stretch left.  You'll be able to fill all your tires, and your buddies tires, without moving the compressor.

The label on the side of the compressor.  Rated at 40 minutes of continuous use, but they recommend on for 20 minutes, off for 30.  Max pressure is 120 PSI.

A few included adapters for filling up everything else.

The next time you air down to go off-road, you might want to upgrade your small compressor for one of these.


There are a number of options to fill up your tires.  You could get a $25 compressor for Walmart, then discover it flames out when trying to refill 4 tires.  Or you could go all out and get a tank of air with a regulator.  Those are expensive and take up a fair amount of room.  I'm also not real fond of having a pressure vessel with a couple thousand PSI in the back of the truck while off-roading.  They also must be refilled or swapped for a full tank.  They do work great, and fill tires FAST.  If you go out every weekend, that might be the hot ticket for you.

I went for something in the middle.  I didn't want to spent a bunch of money on a big name brand model, like the VIAIR compressors.  Instead, I bought a Q-89, which is the big brother of the popular MV50 model.  These are Chinese knock-offs of the VIAIR brand.  They've had quite good reviews.

The chuck on the compressor is a constant bleed type since it has no pressure switch.  It threads onto the Schrader valves.  It pumps quick enough to watch the dial move. 



I've had the compressor 5+ years now.  Still working great.  About the only downside is the lack of having an air tank.  Can't use air tools, and isn't very effective to blow the sand/dirt out of the back of my truck.  As it turned out, a coworker made a working air compressor from two broken ones, for a friend of his.  The leftover 2 gallon tank, and pressure relief valve, was being scrapped.  I snagged the parts, mounted everything to a scrap piece of Lexan with tie wraps, purchased an 85-105 PSI pressure switch from Amazon, and a few fittings & hose from my local Ace Hardware store, and ended up with a very useful setup!  The tank is a little small for air tools, but works great to blast dirt out of the truck, and fill tires even quicker (pre-fill tank before connecting air chuck).  I used 3/8 air hose and fittings to maximize the air flow.  I might also carry a larger diameter air hose if I need to use an impact wrench.


I "bench tested" the setup to make sure this would work.

This compressor pulls almost 43A, so make sure you use heavy gauge wire.  I will be running 6 ga wire from the battery, to where the compressor is mounted in the bed of the truck.  Also will be putting in a fuse near the battery end, which will protect the wiring.

I charged up the tank, and did a decay test to make sure there were no leaks.  FWIW, this compressor EASILY restarts at 100 PSI.  This was before the automatic pressure switch was put in series with the compressor power switch. 

The power switch is connected to an 80A relay inside the black box.  The relay carries the heavy current of the compressor motor.  Be sure to put the pressure switch on the control side (low current), not the load side (43A), or you'll buy another $16 pressure switch!  If you look closely, you can see the two conductor wire running from the pressure switch, into the power switch box.  A few tie wraps kept the wiring neat.

The compressor & tank will live in the front of the truck's bed.  The bed has a rollup metal cover that hides everything, and keeps most of the rain out.  The drum where the cover rolls up, is just above the compressor.  Everything fits nicely underneath.  I could have mounted the tank in a different position if needed, or moved the fittings.

I will have a remote switch in the cab, and have already run an airline to the tailgate.  I carry two 25' coiled airlines onboard.

With the heavy rains in FL, rain can still get past the rollup cover.  To keep water off the compressor when not in use, I sewed a waterproof cover from Sunbrella fabric.  Ain't perfect, but it's functional.

A ratchet strap holds the air compressor, a toolbox, and a Xantrex PowerPack in place.  I can easily pull the cover off the compressor without having to step into the bed of the truck.



I had been using my portable jump pack as a power source for the compressor, but that's a PITA.  I ordered some 6 gauge power cable, and bought a heavy duty fuse block.  Routing wires under the hood, under the chassis, and into the bed of the truck is a time consuming task.  I probably spent two hours last night hiding the cables as much as possible, and keeping them away from things that move or get hot.  Here's a number of pictures that show part of the effort.

I put both power cables near the battery, with some room to spare, then tie wrapped them in place.  As the cables are routed, they are put in split loom when possible, and tie wrapped to existing cables.  I needed about 25' of 6 gauge cable, so I bought 30' of black and red flexible welding cable.


The plastic cowling under the windshield intended to route rain water away was a good spot to get the cables from one side of the engine compartment to the other, while staying away from the engine.  I used a Greenlee Fishstik to pull the cables through the existing openings.

A little electrical tape was all that was needed to attach the cables to the Fishstik.

Welding cable is grippy stuff.  It doesn't slide easily.  So a couple of feet of cable had to be piled up at the supply end, then it could be pulled.  Took a while to get all the cable pulled through, and would have been much quicker with two people.

Small automotive fuses won't do.  This compressor draws 43 Amps running, and can spike higher than that.  I opted to go with a 60 Amp Maxi-Fuse.

The fuse block is made by Blue Sea.  This is often sold at marine supply stores.  Ring terminals were crimped onto the 6 ga cables, and a stainless steel fender washer and lock washer secured them in place.  A piece of heatshrink on each cable prevented any accidental shorting to the chassis (ground).

Three self tapping screws secured the fuse block to the frame near the battery.

The dust cover was installed.  This is prior to the cables being put in split loom, and secured to the nearby factory wire harness.

From this view, the location of the fuse block in relation to the battery is easily seen.  The fuse block needs to be close to the battery to protect as much of the wiring as possible.  The cable had not yet been connected to the battery in this picture.

To connect the cables to the battery, these are the type of lugs used.  The factory battery cable clamps use a nut and bolt to clamp the battery cable to the battery.  I removed the nut from the clamp, slipped a terminal lug onto the bolt, and replaced the nut.  Very simple.

Might take a few more pictures once all the split loom is installed.  My goal is to have all my modification hidden in plain sight.

Here's a short video testing whether or not it can effectively remove and replace the lugnuts on my truck.






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Last updated 05/03/12    All rights reserved.