pressure switch problem?

[mesmydo]

I am new to air suspension and this my first air ride setup car,so I hope this is not a stupid question,but when I finished the install and powered up the compressor to fill the tank it seemed like it was taking too long to fill and would not shut off ,so I shut it down so I wouldn't hurt anything. With the set up I have the pressure switch would not coneeect directly to the compressor,so I was told to connect it at the tank. Are there positive and negative terminals on the switch or does that not matter. I have the switch tee'd into the connection on the in-side of the tank.How long should it take for the tank to fill and shut off when I initially filled it??

[britt@ridetech.com]

what size tank do you have? What compressor are you using?

The pressure switch is a simple on/off switch (think of a light switch). It can be connected to either positive or negative. Are you using a relay?

[mesmydo]

I have an ARC 4000 set up with a 3 gallon tank and a ARC5001 compressor. No relay,just what came in the kit.

[britt@ridetech.com]

How have you connected the wiring? Are you using the pressure switch on the +12V wire, or on the Ground wire of the compressor? Either is fine, but I usually switch ground.

[mesmydo]

I have the compressor grounded to the chassis and the red wire to the switch and then I have the other pole of the switch running to the 12v with the fuse inline. Is the side of the switch with a white dot next to it the + or -, or does that matter?

[britt@ridetech.com]

the switch does not have a positive/ground, you simply wire it like you have. It's normally closed (power flowing through the switch) when the pressure is below 135psi, it then opens (stops power flow) when it reaches 150psi.

A thomas 327 takes about 4 minutes to fill a 3 gallon tank from zero to 150psi. Turn it on and let the compressor run for a while. If it does not shut the compressor off after 5 minutes or so you may want to hook a manual gauge to the tank to see if it goes over 150psi. The switch may be bad, but they are VERY reliable so I think you just have not let it run long enough.

[mesmydo]

Thanks Britt, I will give it a try. As long as I have a thread going could you help me with one other thing. I have the system up and running ,other then the switch problem and when I inflate all the bags, one of the rear shockwaves slowly loses pressure over a 3-4 minute time frame. I checked the fittings with soapy water and couldn't find a definite leak , so I swapped the lines on the rear shocks from side to side and the leak moved to the other side with the line. I thought that maybe that section of line had a leak so I put a new section of line in, but it still leaks. Is there any possibility that one valve of the assembly is bad or am I missing something?? I also changed the fittings out at the shock and the valve assembly, but it didn't stop it.

[mesmydo]

Hey Britt, I gave it time to fill and it shut off. I guess I was just being a nervous Nelly. I really can't afford to replace the system if I blew it up , so I was being overly cautious. After the system got up to pressure the leaky shock stopped leaking. Did the connections need to get up to full pressure to seat up or something?? Anyway ,Thanks again for all your help, Greg

[britt@ridetech.com]

The pressure in the tank helps keep the valves closed. If the pressure in the tank drops more than 50psi below the bags they leak back through the valves.

[daren springett]

HEY Britt,emailed you some questions hope you can answer them. As to this thread is it possible for the psi to drop 50 below the psi in the bags even while using the rideproe2. since the compressor kicks back on at 135 minimum?

[britt@ridetech.com]

In normal operation the tank psi cannot drop below the bag psi as it is impossible for the tank to push more psi to the bags than it current has. So if your bags are at 100psi, the tank can only deplete to 100psi. It cannot push 130psi to the bags and leave 90psi in the tank. It's against the laws of physics.

Now if the tank has 130psi it can push 130psi to the bags. This is all dependent upon how much volume the tank holds and how much volume the bags consume.

[daren springett]

can you explain the relation of psi and volume. I know that volume is based on size of the tank, so a 5 gal tank holds 5 gals of air,but if a pressure switch kicks off a compressor at 200 psi, that means that the air in the tank would be pressurized at 200 psi ,correct? Does it remain at that pressure if i use lets say 2 gal of air to fill my bags, does the remaining 3 still have that pressure? what is the advantage of 150 psi vs. 200 .does it fill faster but harder to control? any effect on the volume ?

[britt@ridetech.com]

WOW, this may take a couple of posts to answer, so here goes:

Pressure and volume affect each other.
Let's do some math with your AirPod tank.

Volume of a cylinder=pi * radius squared * height
V=3.14*12.25*31.125
V=1197.22
So your tank holds 1197cubic inches of air at standard atmosphere (14.7psi).
(1 US Gallon=231 cubic inches, so 1197/231=5.18 gallons)

Now let's compress the air and see how much air we actually put in the tank at 150psi:
Va = pc Vc / pa (1)
Volume at atmosphere = compressed pressure * compressed volume / atmosphere pressure
Va=154.7psi * 1197 / 14.7
Va=12597 cubic inches
(1 US Gallon=231 cubic inches, so 12597/231=54.5 gallons)

As soon as you open a valve you no longer have 12597 cubic inches in the storage vessel. The higher pressure in the tank has allowed the air to be pushed from the tank through the open valve to the air spring. So now, you have to consider that the tank is being depleted, while the bag is being filled.

Once the two equal in pressure (lets say at 100psi for example), air can no longer be pushed to the air spring. The only way to push more air is to increase the pressure in the tank to something higher than 100psi or increase the size of the air spring (as volume increases pressure drops). However, we are stuck with the air spring size, so the volume of the air spring must remain.

[britt@ridetech.com]

One solution is to increase the pressure of the storage vessel; so let's try that:

If we raised the pressure of the AirPod tank to 200psi:
Va=214.7 * 1197 / 14.7
Va=17482.7 cubic inches

So increasing pressure from 150 to 200psi increased the actual amount of air by 38.8%. But the higher pressure also provided more "push".

Now don't rush out and buy a 200psi pressure switch. Our systems are designed to run at or around 100psi at ride height (in general). We've done enough vehciles to be able to make an educated guess as to which compressor system will raise the vehicle back to ride height without running out of air.

In extreme cases, where the bags are very large so they take more volume, or small bags that require a higher pressure we normally add storage volume to address the issue, not a higher pressure. When running a higher pressure the compressors have to work MUCH harder to compress the air, which shortens the life of the compressor.

[daren springett]

Thanks Britt, anawered all my questions even the emailed ones. So I will think possitive that the larger airpod will most likely solve my issues!!