Am having problems getting this question answered form parts suppliers.

I have a Powermate 6hp 2 stage compressor. A few weeks ago I noticed what I thought was a new noise while it was running. I traced the noise to hot air coming from what I eventually learned was the "Bleeder" or "Unloader" valve that is mounted to the side of the pressure switch.
It didn't seem to be logical for high pressure air to be vented while the compressor was running.

As I understand it the bleeder valve is intended to bleed off the high pressure in the compressor cylinders and line from the compressor to the tank when the compressor motor stops. This allows for easier starting. I posed the question to a couple of on-line companies that sell parts for the compressor and they keep giving me the answer that I need to test the check valve because a faulty check valve will allow the tank to leak and loose all its pressure. I have tried telling them that my tank does not leak and holds 150psi just fine. They don't seem to understand my question. (I think they are just order takers and don't really understand air compressors). They keep telling me to pull the line to the bleeder valve and see if air is leaking out. If it is this means the check valve is defective.

The best I can figure out is that there is an actuator in the pressure switch that should open the bleeder valve when the motor is not running but allow the bleeder valve to close when the motor is running. If this is what is suppose to happen then either the bleeder valve is defective and is open all the time or the actuator in the pressure switch is defective and is keeping the valve open all the time.

Am I correct in my analysis?

Ideas on how to test?

replacement bleeder valve is $25-$30
replacement pressure switch is $150+

I do not support the approach of change the parts till the problem goes away.

If it's possible I'd first try to remove the unloader valve and clean it. Could be a bit of scale/rust or something in there keeping it from snapping shut.

Your theory of operation is stated correctly.

Thanks will check the valve.

I did do a test of pulling the valve off the Pressure switch. I notes a small metal pin in the plastic body was out but it seemed to move OK.

With the unloader valve disconnected from the pressure switch there was no bleed off of high pressure air. This might mean that either the unloader valve is stuck open. or the pressure switch actuator ? is stuck in the "open valve" position.

Hope it is the valve. Will check the pressure switch actuator and see if it is stuck in the on position and it doesn't allow the bleeder to close. (Hope this is it otherwise its a new switch ($150+)