2014 prostar n13 compressor / dryer issue?

First post but I've been lurking for more than a year. Great people and information here! I have been having issues for almost a week straight with my n13 prostar.

Back when NJ had a cold snap in February the purge valve on my bendix ad-is had a very faint steady leak running or not and would only leak down to about 60psi overnight. When it warmed up to the teens+ I had no leak running or not.
Now for the past week I believe I have a totally separate issue. I run local 100-300 miles per day and in the afternoons my compressor kicks in normally , but when it purges at about 125 the compressor doesn't disengage (I can hear it thumping through the air filter) and the purge valve constantly leaks. When the engine is shut off the purge valve stops leaking. When the compressor is building air to purge psi I have no leaks. The mechanic (for the company trucks) at the company I'm leased onto was nice enough to give me his opinion and told me to replace the whole dryer.
I was able to find a thread about this issue but It died before any answer was posted. So far I have sprayed every air line with soapy water and found an very small leak in the purple aux line going to the fan clutch I repaired the leak and still have the same issue. I have no oil / moisture in my tank main tanks. I don't know how the purge tank works and wasn't able to find anything on troubleshooting it, but when the truck is leaking the purge (wet tank?) bleed valve has almost no pressure.

I do have the ba-921 compressor so replacing the unloader is achievable except for access. I assume the black plastic fender has to come off to get my hands close enough to the compressor to change it.

Sorry for the novel and thanks for any input!
I can get a whole new ad-is assy for $700 tomorrow as well as individual components (unloader, governer, purge valve. I also found an automann dryer assy for $300 but I know nothing about the quality of the product.
Thanks Again!

 

Thanks heavyd for your insight! That's what I'm going to try tomorrow. I spoke with bendix tech support about the issue and they were thinking the same thing. The tech mentioned that since it's purging, but the compressor is not kicking off the governor is doing its job. Picked up the unloader kit this afternoon. Anything else I need to get out of the way to make the job easier besides the plastic splash guard? Don't say fuel tank because I just put 500 lbs in it this afternoon!