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How-To: Simple Onboard Air for your TJ/LJ (Viair 400H)

Mr. Bills

TJ Addict
Joined
Nov 24, 2017
Messages
2,110
Location
Area Code 530
Here are some photos of my simple onboard air system utilizing a Viair 400H hardmount compressor:

The Compressor:

Compressor Installation.jpg
Compressor Installation front view.jpg



Electrical:

The factory 12 gauge wiring was replaced with a 12" 10 gauge leader and 2-pole connector.. Power for the compressor comes directly from the battery via a Blue Sea 5024 battery terminal fuse block and 10 gauge wire fused at 40 amps per Viair recommendations.

Factory Wiring
Viair 400H factory electrical wiring.jpg


After rewiring with 10 gauge zipcord
Rewired Compresssor with 2 Pole Connector.jpg


Factory Switch and Upgraded Wiring.jpg


Blue Sea Battery Terminal Fuse Block (P/N 5024)
Blue Sea Fuse Block.jpg




Check Valve, Leader Hose and Hose Connections:


Plumbing at compressor head:
Plumbing at Compressor Head.jpg



End of leader hose:
Stud at end of Leader Hose.jpg





Rather than a step-by-step "How-To," here are the main points:

1. The mounting plate is a 4 3/4" x 12" piece of 11 gauge steel I found in the scrap bin of my local metal supply house ($1). I cut down an old neoprene mouse pad to cushion between the mounting plate and fender, but in hindsight it was probably unnecessary.

2. I purchased a 10 gauge 2-pole connector on Ebay. It came with 24" of wire between the connectors so I was able to cut it in half and wire one half in place of the smaller gauge wire provided by Viair from motor to switch. This allows me to simply unplug the compressor if the unit needs to be removed. [Be sure to pay attention to which way the plug is oriented. The "+" side should be protected and "-" side exposed on the battery side and the "+" side exposed and "-" side protected on the compressor side. That way there won't be a hot 12v + prong exposed when the compressor is disconnected from the battery.]

3. I wired the compressor with a 10' piece of 99% copper 10 gauge zipcord that I found on Ebay, and utilized a Blue Sea #5024 battery terminal fuse block and 40A fuse (recommended by Viair even though their portable 400P and 400P-A compressors come with a 30A fuse). I used a second 10' piece of 10 gauge zipcord and 30A fuse for my radio communications and some 12 gauge wire with 20A fuse for the connection to my Battery Tender 3 amp charger. Wiring couldn't have been simpler, and should the need ever arise I can easily isolate the compressor/communications/auxiliary battery charging systems from the rest of the electrical system.

4. The 400H comes pre-wired with a switch and water resistant cover. I decided that there is no need for a switch in the cab for an open chuck (i.e., tankless) system, and I have no issue with raising the hood at the end of a day offroading in order to turn the compressor on and off. This allows me to check the oil, coolant, etc. at the same time.. The mounting location stays dry in inclement weather and if I ever detail my engine all I need to do is put a plastic grocery bag over the compressor before spraying down the engine bay.

5. At the compressor head I could have used a simple 1/4" NPT street elbow, barbed fitting, 3/8" remnant air hose from Harbor Freight and a connector stud, but decided to address the heat buildup at the head and the possibility that hot air from the compressor could damage the leader hose. I used a "bar stock" brass tee because the additional mass of the brass acts as a heat sink to absorb heat from the compressor head, as does the Viair check valve and brass barbed fitting. I also used a 22" length of high pressure, high temperature 3/8" hose as a leader hose (expensive @ $4.95/ft., but I didn't need much).

6. A check valve isn't necessary in an open chuck (i.e., tankless) air system, but it ensures that there will never be pressure on the piston when the compressor starts. Such soft starts put less stress on the compressor and require fewer amps to get the motor turning.

7. I purchased a swivel stud rather than a standard stud which made it easier to route the air line when the system is hooked up.

8. Keep your eye open for good deals on compressors. Amazon often has the 400H on sale. I acquired a "pre-owned" compressor from a friend for $50.



Inflation/Deflation System

Set up for inflation:
Complete Inflation System.jpg


Set up for deflating two tires at once (remove the green hose to deflate a single tire):
Set Up for Deflating Two Tires at Once.jpg


Set up for deflating a single tire:
Set Up to Deflate One Tire.jpg


Close Up of the Manifold
Close Up of Manifold with Gauge.jpg


The "You'll Shoot Your Eye Out" Ralph Nader Memorial Nanny State Pressure Relief Valve and Safety Device
Ralph Nader Memorial Safety Device.jpg


Test Port and Pressure Relief Valve with Gauge.jpg


All of the hoses, fittings and spare parts fit in this bag:

Tire Kit Bag.jpg



Hope this helps someone.
 
Last edited:
OP
Mr. Bills

Mr. Bills

TJ Addict
Joined
Nov 24, 2017
Messages
2,110
Location
Area Code 530
Which compressor is that?
That is a Chinese MV-50 aka MF-1050. They are relatively inexpensive, but you get what you pay for. They are slow, the output is insufficient to air up 35" tires without overheating the motor, and iffy for 33's. The reed valves are notorious for failing. In the long run they are no bargain. [BTDT.]
 

Xposure

TJ Enthusiast
Joined
Jul 13, 2018
Messages
401
Location
Trussville, AL
That’s a nice write up....it’s good to see that the 400h compressor fits there. I’ve been considering the 400P auto but not sure where it’ll fit. Seeing yours gives me a better idea of what will work.
 

DHunt

TJ Enthusiast
Supporting Member
Joined
Jun 12, 2018
Messages
231
Location
Harbison Canyon
Found it on Amazon. They call it a boat part and charge $45. That's because while JEEP means just empty every pocket, BOAT means break out another thousand.
 
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Xposure

TJ Enthusiast
Joined
Jul 13, 2018
Messages
401
Location
Trussville, AL
Here are some photos of my simple onboard air system utilizing a Viair 400H hardmount compressor:

The Compressor:

View attachment 38604 View attachment 38605


Electrical:

The factory 12 gauge wiring was replaced with a 12" 10 gauge leader and 2-pole connector.. Power for the compressor comes directly from the battery via a Blue Sea 5024 battery terminal fuse block and 10 gauge wire fused at 40 amps per Viair recommendations.

Factory Wiring
View attachment 38606

After rewiring with 10 gauge zipcord
View attachment 38607

View attachment 38608

Blue Sea Battery Terminal Fuse Block (P/N 5024)
View attachment 38609



Check Valve, Leader Hose and Hose Connections:


Plumbing at compressor head:
View attachment 38610


End of leader hose:
View attachment 38612




Rather than a step-by-step "How-To," here are the main points:

1. The mounting plate is a 4 3/4" x 12" piece of 11 gauge steel I found in the scrap bin of my local metal supply house ($1). I cut down an old neoprene mouse pad to cushion between the mounting plate and fender, but in hindsight it was probably unnecessary.

2. I purchased a 10 gauge 2-pole connector on Ebay. It came with 24" of wire between the connectors so I was able to cut it in half and wire one half in place of the smaller gauge wire provided by Viair from motor to switch. This allows me to simply unplug the compressor if the unit needs to be removed. [Be sure to pay attention to which way the plug is oriented. The "+" side should be protected and "-" side exposed on the battery side and the "+" side exposed and "-" side protected on the compressor side. That way there won't be a hot 12v + prong exposed when the compressor is disconnected from the battery.]

3. I wired the compressor with a 10' piece of 99% copper 10 gauge zipcord that I found on Ebay, and utilized a Blue Sea #5024 battery terminal fuse block and 40A fuse (recommended by Viair even though their portable 400P and 400P-A compressors come with a 30A fuse). I used a second 10' piece of 10 gauge zipcord and 30A fuse for my radio communications and some 12 gauge wire with 20A fuse for the connection to my Battery Tender 3 amp charger. Wiring couldn't have been simpler, and should the need ever arise I can easily isolate the compressor/communications/auxiliary battery charging systems from the rest of the electrical system.

4. The 400H comes pre-wired with a switch and water resistant cover. I decided that there is no need for a switch in the cab for an open chuck (i.e., tankless) system, and I have no issue with raising the hood at the end of a day offroading in order to turn the compressor on and off. This allows me to check the oil, coolant, etc. at the same time.. The mounting location stays dry in inclement weather and if I ever detail my engine all I need to do is put a plastic grocery bag over the compressor before spraying down the engine bay.

5. At the compressor head I could have used a simple 1/4" NPT street elbow, barbed fitting, 3/8" remnant air hose from Harbor Freight and a connector stud, but decided to address the heat buildup at the head and the possibility that hot air from the compressor could damage the leader hose. I used a "bar stock" brass tee because the additional mass of the brass acts as a heat sink to absorb heat from the compressor head, as does the Viair check valve and brass barbed fitting. I also used a 22" length of high pressure, high temperature 3/8" hose as a leader hose (expensive @ $4.95/ft., but I didn't need much).

6. A check valve isn't necessary in an open chuck (i.e., tankless) air system, but it ensures that there will never be pressure on the piston when the compressor starts. Such soft starts put less stress on the compressor and require fewer amps to get the motor turning.

7. I purchased a swivel stud rather than a standard stud which made it easier to route the air line when the system is hooked up.

8. Keep your eye open for good deals on compressors. Amazon often has the 400H on sale. I acquired a "pre-owned" compressor from a friend for $50.



Inflation/Deflation System

Set up for inflation:
View attachment 38615

Set up for deflating two tires at once (remove the green hose to deflate a single tire):
View attachment 38616

Set up for deflating a single tire:
View attachment 38617

Close Up of the Manifold
View attachment 38621

The "You'll Shoot Your Eye Out" Ralph Nader Memorial Nanny State Pressure Relief Valve and Safety Device
View attachment 38618

View attachment 38619

All of the hoses, fittings and spare parts fit in this bag:

View attachment 38620


Hope this helps someone.

Bill, when you mounted your compressor is it attached to the abs bracket or somewhere else?
 
OP
Mr. Bills

Mr. Bills

TJ Addict
Joined
Nov 24, 2017
Messages
2,110
Location
Area Code 530
The bracket is a 4 3/4" x 12" piece of 11 ga. steel plate bolted to the top of the inner fender in three places - one in common with the cruise control bracket using a longer body bolt than the body bolt utilized by the factory for the cruise control bracket with a small spacer made from a couple of washers epoxied together between the cruise control bracket and the compressor mount to make the mount level. The other two fasteners were 1/4" stainless steel bolts and nuts through holes drilled through the top of the inner fender well.

The ABS assembly is attached to a horizontal surface at the firewall located lower down and behind the fender well - my setup does not use that surface nor does it extend into the "air space" above it. My Rubicon does not have ABS (thank goodness) so I didn't have to contend with those parts when choosing a location for my compressor mount.
 
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OP
Mr. Bills

Mr. Bills

TJ Addict
Joined
Nov 24, 2017
Messages
2,110
Location
Area Code 530
^^^ The Amazon single piston compressor does fit the ABS tray. I just couldn't bring myself to pay $275 for a small compressor and was fortunate to be able to buy my Viair 400H compressor for only $50.
 

tacman605

New Member
Joined
Nov 14, 2018
Messages
15
Location
Arkansas
That is one heck of a system, but beyond my mechanical/electrical ability so I went with a simple 10 lb CO2 set up with a 150 regulator mounted behind the seat.