Ok, so now I’ve gotten 3 different pressure switches from Horn Blasters, and NONE of them will let the system get to more than 132psi. I JUST got a new one today, installed it, pressurized the tank, and guess what… 132psi.
The gauge gets up to 136 but when the compressors shut off, it “levels out” at 132. I am using the Dakota Digital 400psi switch from HB. When I release the pressure from the tank, it turns the compressors on at 110psi, like it should.
If ANYONE has had this problem, please let me know what you’ve done to correct it.
You’ve misunderstood… the Digital sender for the digital pressure gauge will read up to 400 psi… I know the compressors will not go past 150, and I have a 110/145 pressure switch installed.
It should be set to read up to 400psi for the best accuracy, and it continously stops at 132-134psi, when it should stop at 145psi.
When installing it recently I connected the digital sender unit about halfway in the main air line closest to where the compressors are connected. This is about 4’ away from the air tank. I purposefully kept a manual gauge mounted directly on the air tank for comparison purposes. This is also helpful if I need to read the tank pressure when the truck is off, when I am inside the truck bed, or when I remove the tank for portable use.
My pressure switch for the compressors is set to come on at or below 110 psi and switch off at or above 146 psi. After installing the system I did a number of tank fills and dumps to test for leaks and compare the gauge readings. I found that the manual gauge on the tank would read anywhere from 140-148 when the compressors cut off and the Air Zenith gauge always reads 144-145. When draining the tank, the compressors kick on just as the Air Zenith gauge hits 110 and the manual gauge reads anywhere from 105-115.
So my interpretation is that the manual gauge is less accurate but at least close with a variance of +/- 5 psi and the Air Zenith gauge appears to be accurate to +/- 1 psi. You also have to factor in the accuracy of the pressure switch which controls the compressors so the Air Zenith gauge might be dead on and the +/- 1 psi variance could be from the pressure switch.
I also noticed that the tank pressure fluctuates throughout the day as temperatures climb and drop, and as I drive up and down steep grades. Sometimes it looks like I have a slow leak that lost 5 psi when I park it at night but when I check it again in the morning it is usually back up to normal or very close to it.
Bottom line is not to worry about a few psi points in either direction. If you suspect your digital gauge is bad or less accurate then compare it to a manual gauge for a baseline. And remember that your pressure switch, air lines, leaks, temperature variations, etc. could be introducing a margin of error as well.
Also make sure that your digital air gauge is grounded to the exact same point as your sender unit. You can do this by running two wires from the gauge to the sender and using one of them for the signal and one for the ground, with the ground wire only connected to the vehicle ground at one end.
are you sure its even the pressure switch? if its the third one you’re on then it could possibly be something else.
i also have the 110/145 switch and mine usually stops at about 140+psi. not a big deal to me really. over night i noticed it would level off around 90psi -prob due to temp drop and minor leak in the airline. not sure if that’s the same problem you’re having though…
but you’re saying the actual compressors shut off at 134ish? maybe something wrong with the tank? i dunno… check for leaks with soapy water.
or maybe it really is a digital gauge error… i dont have one of those so i wouldnt kno…
heres what you do… go get you a regular old dial guage and test it it could be the digital sender not reading right… test it with more than one guage before you blame the pressure switch…
ok, So not to open up an old thread, but here are some interesting findings…
The Dakota Digital gauge is supposed to be very accurate right? Atleast that is what I thought. and then I found this… I went to a local hydrolic shop so that I could get some more 3/8" air line because I don’t like the viair air source relocation kit (too small of an opening for air to get through to fill tires and what not) and I ended up getting the air line, and a mechanical pressure gauge while I was there… well, not happy with the dakota digital gauge anymore… 15psi difference in the 2 gauges
Did you mount the pressure sensor in the same location as your manual gauge? I know they should be the same but if you have the pressure sensor mounted after a regulator, series of fittings, hoses, etc. then the extra stuff might be causing a pressure drop along the line.
My digital gauge from Air Zenith agrees almost exactly with the manual gauge which I purchased from Lowes for $10. Also don’t rule out an error in the manual gauge, but if your cutoff switch is designed to stop at or close to 150 then your manual gauge is probably right.
I would make sure to ground the digital display to the same exact point in your vehicle as the sensor - via the same wire. This will ensure a more accurate reading.
