How to add a pressure switch to a Smitybilt compressor

[danbrown]

Hello!
For those of you who have a Smitybilt compressor you know how annoying it is to have it run constantly. Here is a quick DIY project where you can add a pressure switch to it, and move away from the Japanese fittings to standard NPT.

Parts needed:

(1) Pipe 1/4" NPT Female x M12 X1.25 Male adapter. This is used to adapt from the M12 female thread at the handle of the compressor to 1/4" NPT female.
Link to fitting

(1) Pressure switch (I used one rated for 70-100psi)
Link to pressure switch

(1) Tee fitting 1/4NPT M x 1/4NPT F X 1/4NPT F
Link to Tee Fitting

(1) ARB Portable inflation kit. This is not necessary. I bought it to change from the Smitybilt yellow hose to the ARB hose which included the 1/4" quick disconnect fittings.
Link to ARB Tire Inflation kit

For wiring you will need some wire and spade connectors. I do believe i used 16 gauge.


Assembly (Note: use teflon tape on all air fittings)

1. Remove the air hose attached to the compressor.
2. The M12 M to 1/4" NPT female screws into where the old hose was just removed.
3. From here it's pretty straightforward. The Tee goes into the adapter, the Pressure Switch goes into one of the female ports of the Tee, and your quick disconnect goes into the other female port (refer to picture if needed).

Wiring

1) Remove the base.
2) Remove the end cap where the on/off switch is.
3) Cut 2 pieces of wire 12" long (you can trim them later) and put a spade (female) connector on one end of both wires. These will plug into the pressure switch (see picture for reference).
4) What you are going to do is wire the pressure switch, the two wires you just put connectors on, in series with the on/off switch.
5) The on/off switch (located in the end cap) has two wires attached to it.
6) Cut the wire coming out of on/off switch towards the middle. You want to leave enough room to splice in the two wires coming from the pressure switch
7) Splice in the two wire from the pressure switch. (please refer to my badly drawn wiring diagram!)
8) At this point neaten up your wiring, put the end cap and base back on.

Test

Connect the compressor up to 12VDC and turn it on. It should run for a couple of seconds and shutoff once there is enough pressure to trip the pressure swich. Once air starts to flow, the pressure switch will close allowing air to flow.

(Note; the wiring diagram shows a lead going from the on/off switch, through the pressure switch to the motor. This is actual the feed to the relay. The power to the motor is handled by the relay)

 

[D4R4x4]

Hello!
For those of you who have a Smitybilt compressor you know how annoying it is to have it run constantly. Here is a quick DIY project where you can add a pressure switch to it, and move away from the Japanese fittings to standard NPT.

Parts needed:

(1) Pipe 1/4" NPT Female x M12 X1.25 Male adapter. This is used to adapt from the M12 female thread at the handle of the compressor to 1/4" NPT female.
Link to fitting

(1) Pressure switch (I used one rated for 70-100psi)
Link to pressure switch

(1) Tee fitting 1/4NPT M x 1/4NPT F X 1/4NPT F
Link to Tee Fitting

(1) ARB Portable inflation kit. This is not necessary. I bought it to change from the Smitybilt yellow hose to the ARB hose which included the 1/4" quick disconnect fittings.
Link to ARB Tire Inflation kit

For wiring you will need some wire and spade connectors. I do believe i used 16 gauge.


Assembly (Note: use teflon tape on all air fittings)

1. Remove the air hose attached to the compressor.
2. The M12 M to 1/4" NPT female screws into where the old hose was just removed.
3. From here it's pretty straightforward. The Tee goes into the adapter, the Pressure Switch goes into one of the female ports of the Tee, and your quick disconnect goes into the other female port (refer to picture if needed).

Wiring

1) Remove the base.
2) Remove the end cap where the on/off switch is.
3) Cut 2 pieces of wire 12" long (you can trim them later) and put a spade (female) connector on one end of both wires. These will plug into the pressure switch (see picture for reference).
4) What you are going to do is wire the pressure switch, the two wires you just put connectors on, in series with the on/off switch.
5) The on/off switch (located in the end cap) has two wires attached to it.
6) Cut the wire coming out of on/off switch towards the middle. You want to leave enough room to splice in the two wires coming from the pressure switch
7) Splice in the two wire from the pressure switch. (please refer to my badly drawn wiring diagram!)
8) At this point neaten up your wiring, put the end cap and base back on.

Test

Connect the compressor up to 12VDC and turn it on. It should run for a couple of seconds and shutoff once there is enough pressure to trip the pressure swich. Once air starts to flow, the pressure switch will close allowing air to flow.

View attachment 218285View attachment 218286

Awesome How-To! Plan to do this soon.

 

[Red_Leaf_Overland]

My experience with my smittybilt compressor was the pressure release valve on it blows off around 60-65 psi. I bought a higher rated blow off for it but never got around to installing it. Maybe it will be a project I tackle once I fix the steering and electrical in the TJ lol.

 

[KonzaLander]

Nice job tackling the biggest problem with the Smittybuilt Compressor!

You might want to consider adding a relay to the system. I see you point out a relay in the wiring diagram, but show the load going through the pressure switch. Those pressure switches are not designed to carry the high amp load of the compressor. It looks like the Smittybuilt compressor has a 45amp current rating. Since it seems like you were inspired by the ARB CKMA12 plumbing, take a look at the ARB CKMA12 wiring diagram and study the pressure switch wiring, you will see it is simply interrupting the trigger that activates the relay and carries almost no load.

 

[smritte]

You might want to consider adding a relay to the system.

^^^^This^^^^

"If" the switch is rated for the current, it will wear quickly. Mine turns back on at 75psi. The pressure in the line will put a small strain on the compressor. This will raise how much current the compressor draws.
Even though you add in a relay, make sure it can handle the load. My compressor is mounted in my vehicle. I run a 30 amp micro relay. It took about 2 years to wear out the contact. This was something I didn't think about when I installed it. Every time it turns on and off (cycling) it wears some. I will be replacing it with a larger contact relay.

 

[danbrown]

Nice job tackling the biggest problem with the Smittybuilt Compressor!

You might want to consider adding a relay to the system. I see you point out a relay in the wiring diagram, but show the load going through the pressure switch. Those pressure switches are not designed to carry the high amp load of the compressor. It looks like the Smittybuilt compressor has a 45amp current rating. Since it seems like you were inspired by the ARB CKMA12 plumbing, take a look at the ARB CKMA12 wiring diagram and study the pressure switch wiring, you will see it is simply interrupting the trigger that activates the relay and carries almost no load.

I don’t believe the load for the motor is going through the on/off switch. It is there simply to trip the relay. My drawing shows one lead going to the motor, which is not correct.

If the on/off switch were to handle full load it would not be wired up with 18 gauge or less wire.

I’ve added a note in my post to correct this.

-Dan

 

[D4R4x4]

I did the pressure switch mod my Smittybilt compressor. I have the 2780 model, the smaller one, but mod works the same. The wire that you splice into from the switch that goes to the motor is not the wire that actually powers the motor. I used a stripper for 20 guage wire, so it doesn't carry much load.

With this model there is a rubber grommet that the main power wires go thru. I just pushed the new wires thru there. I also reused one of the boots from a Smittybilt hose connector on the switch. It fit nicely and covers up the spade connectors for a clean look. I also put some new connectors on the guage so I can still use it.

Mod was pretty easy and works good. I just wanted to share my experience with everyone to help with ideas. Thanks for sharing the How-To @danbrown .