ARB Twin won't turn off -- solved - pressure switch

I've isolated where air is leaking out of the twin compressor. Circled below are some sort of pressure caps. My guess is air fills the chamber pushing that ball towards the cap compressing the spring. Eventually that pressure gets to the max and the compressor turns off.

In my case, I can feel air continuously coming out of these caps so the compressor never turns off.

1. I can put my thumbs over the caps > the chamber fills > the compressor turns (since it's full of air).
2. I raise a thumb > air escapes > the compressor turns on. At this point, the air is always escaping so the compressor never stops.

Anyone know a fix? I do have an email to ARB support - they were quick with the original asking me to replace the relays. I did that -- same result. But this is also when I discovered where air leaks so I'll see what they come back with.

Thanks in advance!

 

looking at this diagram I can see the parts but it's not clear to me why mine would go bad - maybe that safety valve poppet isn't creating the necessary seal, but I find it odd both chambers have the same issue and they came about at the same time.

https://www.arb.com.au/assets/air-lockers/3-05.pdf

 

I'm not familiar with the design, but if those are safety relief valves and they're both lifting to vent, then you're developing more pressure than intended. I think you said you can block them to prevent air venting and the compressor shuts off and holds pressure, starting up when you unblock them causing pressure to drop.

If that's the case, I'd look at your pressure switch in the system. Sounds like it's now set at just higher than the SRV limits.

 

The springs and cap are doing the right thing … but the pressure switch is too high - is that what you’re saying? Makes sense if so. When I put my thumb on it stops almost immediately.

anyone know if you can adjust the pressure in those switches. Or just get a new switch?

 

Probably not in the type ARB uses. It’s just a switch with a low and high for on and shutoff trigger thresholds.

 

Exactly. Either the springs weakened over time (like you said - doubtful it'd happen to both at the same time) to just below the setpoint of the pressure switch, or somehow the switch setpoint crept up over the spring rate just enough to crack the valves.

You could take yours out and just give it a once-over to see if there's any dirt or corrosion or something out of place. If you have a trusted gauge in the line, plug the relief valves and see what pressure the compressor shuts off at.

Just checked Amazon and you can get a replacement generic for a few bucks in a wide range of pressures.

 

This sounds very much like a pressure switch to me. You can get the switches, though a quick look at Amazon doesn't show any that are the exact same range.

Cut in isn't as important as cut out, you'd be fine with a 120/150. The CKMTA12 manual shows cut in/out of 135/150. The compressor will run a little longer with the lower cut in but it shouldn't be an issue, pretty sure this compressor has a 100% duty cycle.

https://www.amazon.com/s?k=pressure...tch+1/4+npt+135-150psi,aps,150&ref=nb_sb_noss

 

thanks all - I ordered #180901 -- 150 open / 135 close switch -- per the parts diagram I found. I hope to report back success when it arrives. I also basically took the compressor apart - those chambers have some gunk that I'm cleaning out.

 

I agree with the other replies that your compressor is likely creating too much pressure, indicating your switch is likely bad. I replaced mine with a lower pressure cutoff for less wear on the compressor, and I don't need the higher pressure for my applications.

$27 HornBlasters 1/4" NPT 90-120 PSI Pressure Switch

https://www.amazon.com/gp/product/B0BWGND2QS/

Also, since you have it apart to check o-rings and clean, also check the internal hardware.



Bolt #32 backed out and caused a catastrophic failure of my compressor. You should be able to access it fairly easily by removing the filter cover #26, 27, 28 (can unscrew it as an assembly).

 

I replaced the pressure switch and it is now working as expected. I did connect a pressure gauge and confirmed it would compress to ~140 and start again ~120 per the gauge I had on hand.

Unfortunately, I also can't get rid of a small leak in the locker manifold caps and one of the locker solenoids where it connects into the manifold. I'm good as long as I don't mind hearing the compressor cycle every 20-30 seconds when my lockers are engaged -- -- Anyone know if I should have o-rings between the manifold caps and the small silver cylinder? I don't have any and I've tigthtened the sh&t out of the 10m end bolts and just can't get the leak to go away.

 

PFTE thread tape?

-J

 

Is the pressure switch located under the cover? - I have the twin compressor installed in the cubbie hole of the bed, I wonder if i'm going to have to take out the whole thing to replace the pressure switch.

 

Yes

 

dammit.

Thanks

 

yeah it sucks getting it in/out of that cubby. My truck is down for awhile (blown engine) so part of the recovery is probably going involve relocating the ARB into the engine.

 

when taking the compressor apart for cleaning, was it a matter of just blowing air thru it and wipe down clean?

or did you replace any gaskets/etc?

going to tackle this soon and want to make sure i have it all planned out

 

I didn't replace any gaskets or seals. I didn't have any on-hand and am not sure there is a seal kit. I just cleaned it all up as well as I could - brake cleaner - and re-assembled. The hardest part was getting the wiring back in place. I'd leave those along with the fan attached to the outer plate if possible haha.