Hi my daf 85 builds up air to 10bar then drop to 8bar it does this about six times before the hand brake comes off, then park brake light remains on up to 1 mile before I comes off too.
This is first thing in the morning then the brakes are fine, park brake light is slow to go out ie at junctions but no brake drag.
apu is at fault..either replace or remove pipe at port 25 and free the non return valve ,but generally replace apu ,you may also have a compressor issue which is causing the valve in the apu to stick,make sure if you change the apu that you have the larger canister ,you may have to drill and lower the apu to accomodate larger canister
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