Onboard air questions....

CurtisP87 · May 25, 2012

Ive been doing some reading for the past few days trying to figure out how to build my OBA, and Im still confused about certain points. I get the general idea, but Im still uncertain about some of the plumbing/wiring design. I know there needs to be some sort of pressure shut-off, to stop the tank from getting too full, but where physically does this need to be? How does the shut-off work? does it just re-direct the air, or does it actually shut off the compressor stopping the air all together? If it doesnt stop the compressor, how do I work it so that the compressor isnt running all the time when its not needed...? Do I need a toggle switch in the cab to control the power for the compressor?

I know you've all seen these questions 1000x, but I couldnt find a write up detailed enough to answer my laymans questions...Thanks for any help!

brinker88 · May 25, 2012

It all depends on how the air will be supplied. What kind of compressor will you be using?

Explorin94 · May 25, 2012

What compressor are you going to run? Will it be an electrical or the A/C Compressor that is always in place. Either way you will need a pressure cut off switch, a continuous run solenoid and a switch to turn it on and off, a one way valve and a pop off/over pressure valve. Here is a wiring diagram of what you will want to do. Now keep in mind that this is an electrical motor but the A/C compreesor will wire the same way. http://www.thedieselstop.com/forums/attachments/f151/10058d1297691405-board-air-system-compressor-wiring.jpg

CurtisP87 · May 25, 2012

I do plan on using the ac compressor on the motor to fill the tank. My plan was to have some sort of pressure valve before the tank to keep it from over filling, and then wire a toggle switch for the power to the compressor into the cab, and just manually turn the compressor on and off ... does that sound feasible?

Explorin94 · May 25, 2012

CurtisP87 said:
I do plan on using the ac compressor on the motor to fill the tank. My plan was to have some sort of pressure valve before the tank to keep it from over filling, and then wire a toggle switch for the power to the compressor into the cab, and just manually turn the compressor on and off ... does that sound feasible?

Look at the diagram that I posted for you in my first response. As for the A/C Compressor on your truck....it isn't that reliable but it can be used as long as you keep it oiled correctly and often.

CurtisP87 · May 25, 2012

I checked the diagram out, but I dont understand what most of those components are, or what they're job is supposed to be...It seems like all that stuff is there to automatically disengage the clutch on the compressor, right? If I could safely do that with a manual toggle switch, it might save me some headache during the installation...It seems like I could just keep an eye on the tank as it fills up, then turn the toggle off and take away power from the compressor when the tanks full.

doorgunner · May 25, 2012

NOPE...it's gotta have a automatic shut-off valve or a pressure relief valve on the tank....BOOM....things happen/you get distracted....BOOM/burn up the compressor..../drain the battery.....SILENCE/blow up the air tank.....BOOM/.....

Pick one of the above.

kunar · May 25, 2012

the wiring is relatively simple. i used the original a/c harness but cut it apart and changed the way it works. from the factory, the relay in that harness is normally closed, triggered to open at WOT. youve gotta pull one pin out of that connector and move it so that the relay is normally open. the power to the coil on the relay needs to be switched with the key as well as through a toggle and through a pressure switch. my pressure switch closes when pressure drops below 90 psi and opens when it reaches 120. by wiring things this way, the compressor will only try to run when the key is on, the switch is on and the pressure is low. obviously the pressure switch goes where it's getting tank pressure. if you've got any questions, feel free to pm me and i will help you out the best i can. i'd rather answer a few simple questions then have you blow up your truck haha.

Explorin94 · May 26, 2012

CurtisP87 said:
I checked the diagram out, but I dont understand what most of those components are, or what they're job is supposed to be...It seems like all that stuff is there to automatically disengage the clutch on the compressor, right? If I could safely do that with a manual toggle switch, it might save me some headache during the installation...It seems like I could just keep an eye on the tank as it fills up, then turn the toggle off and take away power from the compressor when the tanks full.

If you can't do the job correctly and install all the needed pieces then maybe you shouldn't be thinking of putting on board air on your truck. Everything that I posted in my first post IS what you WILL need to get the job done and get it done the right way. As Doorgunner said you could get distrated and then you have a big ole mess as well as maybe hurting yourself or someone else in the process.
My on board air is set up with all those components and it turns on at 80 PSI and off at 175 PSI. The solenoid supplies the power the pressure switch tells the solenoid when to shut off and turn on. I have a 200 PSI pop off/over pressure valve and a check valve/one way valve. I found all the pieces at Grainer minus the solenoid and have less than $45 in it all. I am using air hose to supply the tanks in the back and 2 old five gallon aircraft oxygen tanks for storage.

doorgunner · May 26, 2012

175psi!!!

that's serious pressure!

all i need is a $40 cigarette lighter compressor that puts out an instant 90psi to keep my 4 indepenedent adjustable air shocks filled at 45 psi....if i carry a heavy load--I fill the rear shocks to 90 psi which is good for about 800 lbs. of cargo...

but an air tank would be nice for my air horns ;missingteeth;

kunar · May 26, 2012

doorgunner said:
175psi!!! that's serious pressure!

all i need is a $40 cigarette lighter compressor that puts out an instant 90psi to keep my 4 indepenedent adjustable air shocks filled at 45 psi....if i carry a heavy load--I fill the rear shocks to 90 psi which is good for about 800 lbs. of cargo...

but an air tank would be nice for my air horns

that little electric thing might be good for your air shocks, but i use mine all the time to fill tires, run air tools and yes, my air horn

i've got an 11 gallon tank under my bed where the spare used to be.

Xploda · May 26, 2012

Get a york a/c pump, they have an internal oil resivoir and last long

Explorin94 · May 26, 2012

doorgunner said:
175psi!!! that's serious pressure!

all i need is a $40 cigarette lighter compressor that puts out an instant 90psi to keep my 4 indepenedent adjustable air shocks filled at 45 psi....if i carry a heavy load--I fill the rear shocks to 90 psi which is good for about 800 lbs. of cargo...

but an air tank would be nice for my air horns

I wanted the 145psi shut off but the guy was out. The lines will hold up to 300psi and the tanks are good to 450psi. It is nice cause it will run an air tool like there is no tomorrow let alone pump up a flat tire pretty quick. It will also pump up both 5 gallon tanks in 32 seconds while holding the throttle at 2000 rpms.

Onboard air questions....

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