the air has stopped building up ?

i'm guessing you are talking pre LF 45 ?? as siad remove compressor pipe at compressor and check pressure coming from compressor then just keep checking at each union till you find no pressure

norb
January 2011

The most common fault on daf 45's when the air wont build up is the compressor head gasket/seals,easy to do and quite cheap but check the air dryer/cartridge and apu valve for contamination and the air system for obvious leak(easy to find........you can hear them!!!)

utah
January 2011