Help with OBA

C7mb

New member
Hi All,

I recently finished up my onboard air setup and have been having issues with my ABR twin compressor not shutting off and wanted to get input from those who are more experienced/have a similar setup.

Heres the main issue: the ARB twin compressor runs until the safety valve on the tank goes off, so I am not sure if its an issue with the ARB pressure switch, or my setup.

My setup consists of the ARB twin compressor pumping into a 7 gallon, aluminum tank (with a stamped maximum working pressure of 150 psi), then into a two-stage filter + regulator combo. All of the lines are with DOT approved 3/8 tubing and quick connect fittings. The tank currently has a 150 psi safety valve installed but ARB recommended I upgrade it to a 155 or 160 psi valve (because the pressure switch is supposed to shut off at 150 psi). I have a 160 psi valve sitting in the garage but I am afraid to install it due to the rated MWP on the tank. I dont believe that I have any major leaks (the tank holds pressure) but I also read that I should have a check valve from the compressor to the tank so that air does not leak through the compressor.

What am I doing wrong? Do I need to replace the tank for one that is rated at a higher MWP? Is it a pressure switch issue?

Thanks!
 

C7mb

New member
Do you have a gauge anywhere in the system so you can see what the pressures are at?

Sent from my SM-G973U using Tapatalk
Unfortunately (stupidly?) not yet, I was looking to build an oled based one but havent gotten around to it yet.

The compressor pressure switch should be lower than the tank max pressure and the relief valve there to protect it. I'd run a pressure switch more like 140 psi personally.
Thats what I had originally thought. I misread the ARB specs thinking the shutoff was 130 PSI so I had a 140 psi safety valve installed before switching to the 150 psi. Should I buy a different pressure switch to swap into the compressor? Is that a modification that other people do?
 

Herbie

Rendezvous Conspirator
Also, when you say "compressor runs until safety valve goes off", are you saying the compressor stops at that point? Or it keeps running beyond that point?

In either case, as others have said, you want the shut-off switch to be somewhat lower than the tank pressure and safety valve. The pop-off valve is only meant to protect against tank failure due to overpressure. (Remember also that pressure can climb after pumping if, for example, the tank gets warm.) Also, it's mechanical, so it can have a variable tolerance, which is probably why it's kicking in before the switch opens.

Looking at ARB's site, I do see some interesting design choices. They apparently only make one pressure switch, the 135/150psi one, and they're selling it with a 150psi tank and 150psi popoff valve. Hopefully the tank' "working" rating is somewhat lower than the real max pressure? If they can assure you the tank isn't a danger at 155 or 160psi, then yes, you can just install a higher-rated popoff valve. Otherwise, I'd be looking at a lower-pressure switch.
 

C7mb

New member
Is this the one you have?


That one appears to come with a pressure switch rated for on/off of 135 and 150 psi. Sounds like it can't reach the off because the relief valve opens first. ARB's recommendation to use a 155 psi relief might work if the switch works reliably. Whether potentially going 5 psi over max working is safe is up to you to decide.
Yes that is the one I have. Ok I will have to do more research. The tank is in the back of the cab on my Tacoma so there is a safety factor to going over the MWP. Thanks!

Also, when you say "compressor runs until safety valve goes off", are you saying the compressor stops at that point? Or it keeps running beyond that point?

In either case, as others have said, you want the shut-off switch to be somewhat lower than the tank pressure and safety valve. The pop-off valve is only meant to protect against tank failure due to overpressure. (Remember also that pressure can climb after pumping if, for example, the tank gets warm.) Also, it's mechanical, so it can have a variable tolerance, which is probably why it's kicking in before the switch opens.

Looking at ARB's site, I do see some interesting design choices. They apparently only make one pressure switch, the 135/150psi one, and they're selling it with a 150psi tank and 150psi popoff valve. Hopefully the tank' "working" rating is somewhat lower than the real max pressure? If they can assure you the tank isn't a danger at 155 or 160psi, then yes, you can just install a higher-rated popoff valve. Otherwise, I'd be looking at a lower-pressure switch.
The compressor continues to run after the valve opens.

Good info, I also thought that the valve was bad and purchased a replacement just to be sure.

Thats what confused me as well. The tanks they sell with their air up kit is rated at 150 psi but they dont say if thats MWP or not. The tech on the phone said that it would be fine going with the 160 psi valve, but he had no idea what my setup was or that the tank was not from ARB. I will do some more research into a pressure switch replacement.
 

IdaSHO

IDACAMPER
Not at all, unless you intend to inflate something to more than 120PSI.

I run a low PSI pressure switch on my OBA setup, primarily (in theory) to increase the life of the compressor.

As I recall, mine is a 90/110PSI switch, which is plenty for inflating my 35" load E tires, so should be more than enough for most peoples' needs.
 

C7mb

New member
Got a chance to install the new pressure switch and everything works correctly now! Thank you guys so much for all of your help and input, I greatly appreciate it!
 

outback97

Adventurer
Got a chance to install the new pressure switch and everything works correctly now! Thank you guys so much for all of your help and input, I greatly appreciate it!
Glad you got it working.

Which switch did you go with? A link or some additional info could be helpful for someone else searching for this in the future.
 
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