Air compressor acting weird

Weird thing: when engine cold starts in the morning compressor cycles every 30 seconds, after hour on the road cycles every 2 minutes

 

Update: I disconnected air intake from air filter to air compressor. Engine was off and air was leaking back to the air filter. So the problem was in the air compressor head. I took apart head and found a lot of burned oil which was sticky and looked like dirt beetween those air valve plates. So I just needed to clean everything , replace gaskets and o rings. I called volvo dealer they said that they dont sell gasket kit and unloader o rings for compressor head . They offered to buy whole rebuild kit $900 or whole rebuilt compressor for $1200 which I dont need. I just need gaskets and o rings. So I found store there they sell all type o rings and also bought gasket material. I cut my own gasket and assembled compressor. Everything works fine now. Cost me arround $7.

 

Here pictures how it look like inside.

 

http://applemachineandsupply.com/
fort pierce, fl
Check on diagram number 18 unloader valve has little o rings on both sides. But to replace them you have to take apart head.