2001 Freightliner fld 120 keeps purging off air every 10 seconds

And you are sure it's purging air? Should be dropping air pressure of it's purging.

 

I would check the Purge Valve on the Air Dryer and check the Braided Air Line from the Governor to the Air Dryer for leaks.

 

Purging where? From the air dryer or from the compressor?

 

The dryer purge signal comes from the governor, which gets air from the wet tank. You will not see any leaks in the wet tank on the dash gauges because there isn't a gauge for the wet tank and the primary and secondary tanks have check vales.

If you are not losing air on the gauges, your left with only 1 thing that could cause excessive purging, an air leak draining the wet tank. This includes the lines to/from the governor, the governor itself, compressor unloader, purge valve, any lines before the check valves to other tanks, hose from the dryer to the tank, dryer check valve, etc. Basically anything that can drain the wet tank when it leaks.

 

Mine was doing the same thing, checked all lines & fittings, replaced governor, unloader valves & purge valve & still didn't fix it. It was the dryer check valve causing the problem.

 

Did you drain your air tanks to make sure they aren't full of water or methyl hydrate or anything? that'll make it cycle.