Air issue, loosing air while parked.

Soapy water and start putting on all air fittings,,,, try the air tanks first.

 

Ive been chasing 1 for a few years- Mine is even more difficult- I lose air ONLY when Im Driving-The Red needle ONLY, Standing still both buttons in-Not a single Hiss-

 

air leveling valves can bleed thru the lever shaft. if you leave the trailer supply pushed in check the gladhand seals,they get cracked and flattened.

 

Fittings under the dash that goes in the splitter, fittings at the air tanks, fittings at the air bags is common in Volvos.

 

Try your parking valve.

 

Do a audible airleak with truck off

Wheels chalked

Have someone help you so you can walk around truck
. have some water and soap mixed in bottle handy

 

Air cartridge is typically a yearly maintenance item. Make it a point to drain your tanks a couple times a week and look for moisture in your hand when it sprays. Pay special attention to the type of moisture, does it smell like oil, water etc which depending can be an indication the seals on the compressor are starting to leak.