DD15 constantly building air and purging every 20-30 seconds.

[HotRod]

I know im a little late on this one, but wanted to throw it out there as well. Sometimes the unloader will hang up in the air compressor as well and not completely unload the compressor, so it continues to build air. When this happens the air will continue to leak out of the purge valve on the air dryer, but with the truck running you will not always hear it. Most guys build up air pressure, then shut the truck off and go look for air leaks. by that time the slight residual air has leaked out the purger valve on the air dryer and the only other thing you will see is small leaks like the one you saw at the fitting. Not saying that is the case with this one, but it is good info on these air systems that will save some time. I agree with the others that any leaks you find it is worth fixing. Just my couple cents!!