Compressor regulator help

[dirtyfingernails]

Could someone please clarify. I recently purchased a takeoff compressor regulator, but it's different than the one I have currently. The old one has a "T" for the larger copper tubing (3/8?) and a port for a return line to the compressor (I'm assuming this turns the compressor on and off). The new valve appears to have 3 ports--see photo. Anyone have this type of valve and could you show me how to plumb it? Thanks. New (take off) one (top photo) has the "T" (1) and two other ports (2 and 3). The old one (on truck now) has two ports (yellow 1 and 2).
Steve

 

[Floridianson]

Sorry edited post. #1 inlet #2 exhaust #3 unloader. Looks like mine has a little cap device that is vented on the exhaust.

 

[rosco]

The regulater in the top picture is very common. I always forget the line routing, so will have to check tomorrow for you. They have multiple ports for line routing. #3 can be move 180, to the other side, or be use where that hex plug is. One of those is a vent, that can be routed to an alcohol sniffer (not the driver), then back to the regulater.

Its not uncommon for a parts house, to swap parts on you, even like different style compressors. The down side of that is that It might take you two days to replumb the thing.

Lee in Alaska

 

[WillWagner]

Floridianson is correct. Leave the #2 port open to atmosphere, or put a vent cap in it...like the one on the differential. The #1 port is a direct line to the tank. It allows the air pressure in the tank to tell the governer to stop the compressor from building more air, it is a sensing line. The #3 port is usually used when there is an air dryer in the system. It sends a signal to the air dryer to "pop off" allowing the dryer to try to purge some of the liquids it collects...water and oil.

 

[dirtyfingernails]

Thank you all for your help. Steve