Air Dryer Purging Air Every 15 Sec

[DVT873]

Is that a Bendix AD-IP ? Thats what it looks like. It looks like your lines are wrong. Below is a link to Bendix. You can get manuals there. Their plumbing pictures could be better. Pay attention to the differences between a Holset compressor and everything else.
First page of the installation directions also shows differences between what they are calling hard seat and soft seat, whatever the hell that is. I noticed that the elbows have black paint on them and the nuts and lines don't. Somebody probaly yanked the old dryer off and didn't pay ant attention to the lines. Which is so dam stupid especially today when everybody has a camera in their pocket. The lines probably had paint on them also.

Once you get the lines sorted out you may still have your origional issue. It is most likely a leak. Take the big line off at the compressor and get fittings so you can connect an airline in from shore. Release the park brakes (chock a wheel) and listen for a leak. Guys say, I don't have a leak my gauges aren't dropping. There are three air reservoirs on any truck. The "wet" reservoir and the primary and secondary. The "wet" reservoir doesn't have a gauge. That is the reservoir that connects to the compressor and dryer.

Somebody mentioned that the lines might be plugged with soot. Or even the reservoir cuttin way down on volume. I think I read about that on here years ago. Came up in a post crash investigation. Below is a link to Bendix. Their phone support used to be the best in the industry. In the last year or so it has really gone downhill. They are hard to get ahold of and it seems a few of the old guys are gone. Below is a link to their site. Click on the manuals tab. Good luck

https://b2bendix.com/MX/en/MXN/Products/.../p/5003424