Air Compressor won't build pressure - Need help diagnosing

Hey all, my old Craftsman 6 gallon pancake compressor just stopped building pressure. Motor runs fine, but the pressure gauge barely moves. I've checked the intake filter and it's clean. Any ideas what to look for? TIA!

Had the same issue with mine last year. Check the check valve - it's that little brass fitting where the tank connects to the pump. They get stuck open sometimes. Also, could be a leak in the tank or a bad pressure switch. Listen for hissing.

^^ What Bob said. Also, if the unloader valve is stuck, it'll vent all the pressure. That's common on those older Craftsman units. Might need to clean or replace it.

Before you tear into the check valve, try this: drain the tank completely, then close the drain and see if it builds pressure with the outlet valve open. If it builds, it's likely the check valve or unloader. If not, could be a reed valve in the pump. Post a vid if you can.

Thanks guys! I'll try the drain trick first and check the check valve. Will report back.