OBA Question...pressure switch

ncgamedog

ncgamedog

Well-Known Member
Joined
Oct 30, 2005
Location
Greensboro, NC
I have OBA on my truck installed by the PO. It uses the factory AC compressor on my 3.4L. There is a manifold made of 2x2 square tube about 6-8" long that the pressure line feeds from the pump. It houses a pressure switch, pop-off valve, quick coupling, and gauge. It then feeds the tank mounted between the frame rails in the rear. The intake is simply the low side hose cut off with a valve cover breather mounted on the end. My truck had something draining the battery and i found that the pressure switch was doing it. Electrically, its fed from a factory fuse box on the pass side wheel well (91' PU) via a piggy back on a 15 amp fuse, then from the switch to a wire on the compressor to engage the magnet on the clutch. It was keeping the clutch on all the time thus causing the drain. The switch looks like any ole' pressure switch on a standard house-hold compressor, it has a lever on the side to turn it off but i could never tell that it worked. NOW my Question is this: Is the switch bad, or wired wrong? or is it that it is not made to work w/ the 12v system? or does that even matter? If so can i get a 12v switch and where?
Thanks so much - J
 
It's wired wrong.
It should be wired with a switch and a relay
the 12 volt source should be one that is only on when the key is on. If you wire it to a continuous 12 volt source I highly recommend you have a switch that lights up when on so you can tell with a glance of the eye you have it on.
 
btw, doesn't matter about 12v vs other...air pressure activates the switch, the electricity only passes thru the contacts. Nothing is electrically controlled.

Is the air working?? Are you always at zero pressure (pump not running), or is the switch not seeing the air build up and keeps running (popoff would blow then). I had to replace my switch last year because it would not turn off.

Like upnover says, run it thru a relay. Mine is set up so the ign has to be on for the pump to get power, because if it sits for a long while, air bleeds out of the tank, making the switch activate...if not switched off, that would lock in the clutch. Did you check for leaks??

DP
 
Its not necessarily wired wrong... (sorry guys) If its using the older style (lever type) well pump pressure switch they are rated for like 20-30amps and can easily switch the compressor on/off.. I'm using that same style for the simplicity (no relays needed) AND they are adjustable.

Take the acorn nut off the plastic housing cover. With that off you should be able to see that when the lever is moved which way is on/off..

It's possible the rest is wired wrong and or the contacts are stuck closed (on) on the switch. The clutch on the pumps usually draw less than 10amps anyway. (mine draws ~5amps) Sometimes just simply cleaning the contacts up will fix the problem..

Mine is run from an ignition hot source to my dash switch to the pressure switch.
 
Im using the same style switch as yager...

I just made mine idiot proof.
I installed a lighted toggle right beside the steering wheel that is a master kill. You have to turn that switch on to allow any electricity to flow to the pressure switch.
I also prefer to leave my tanks empty between uses, but thats personal preference, because I used all rubber hose and not copper tubing.
 
SkyHiK5 said:
Im using the same style switch as yager...

I just made mine idiot proof.
I installed a lighted toggle right beside the steering wheel that is a master kill. You have to turn that switch on to allow any electricity to flow to the pressure switch.
I also prefer to leave my tanks empty between uses, but thats personal preference, because I used all rubber hose and not copper tubing.
Click to expand...

this is exactly how I did mine as well on my CJ. However, it was not wired into the ignition as it was easier to wire to the toggle switch only.

Looks like the easiet thing to do is install a toggle switch so you can turn it on and off as you need it. That way you won't always be running the compressor or draining the battery when you are out crusin' the mall
 
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