new compressor help

[sickboi55]

so im still undecided on what to do about my motor. but im looking at unloader and check valves, i dont know where they are or if i have them. right now i have the piping that goes to the tank from the compressor and a d squared pressure switch, which has 2 fittings. one is open ( i assume for a gauge), the other has the "thing" that you pull the ring to let air out, what is that. also, on my heads there are 2 plugs, one opens to the exhaust valve, the other to the intake. on some pictures ive seen of my compressor there is a pipe joining each of these ports, what is that? lasty, what spec do you go by for the check valve and unloader valve.
here's my original post http://www.garagejournal.com/forum/showthread.php?t=61969

 

[Art From De Leon]

The "thing" is the pop-off valve. Pull on it to see if it working, and not stuck.

 

[sickboi55]

what about an unloader valve and the check valve.

 

[sickboi55]

this is the pressure switch i have:http://www.grainger.com/Grainger/ww...25x&op=search&Ntt=9013ghg2j25x&N=0&sst=subset
does it have a built in unloader valve? if so, is it as effective as one before the reciever? it is fatory set at 80psi max, is that adjustable?
also, i tore the whole thing down today. i do have a check valve (a mueller brand 200wog that i assume is the check valve, it has a little flapper in it, and is before the reciever but doesnt have an unloader. hence my confusion about my pressure switch.

 

[sickboi55]

i actually just read the additional info tab on the link, and it says "Unloader models feature a small valve that opens at shutoff, releasing air pressure from the compressor head". so my first question about having an unloader is answered. but everything i read says an unloader should be before the check valve.

 

[Major Ramifications]

Yes, you need to unload between the head and check valve. If the unloader is on the tank side of the check, it will drain the tank every time you shut it off, and would't unload the head pressure when needed.
Also, some checks have a built in unloader, and some unloaders are attached to the pressure switch.

 

[Salem747]

The "open" fitting should be the opening for your unloader. Once the pressure switch shuts off the power to the motor it has a little pin that opens this valve and lets the air between the head and the check valve escape.

But there should be a line that comes from the check valve to the pressure switch to drain the head pressure through the unloader.