Ken Brown Posted May 14, 2019 Share Posted May 14, 2019 Have 1980 R600 changed back from body truck to Prime mover as was original, having trouble getting air through truck tractor protection valve to trailer. valve is very hard to push in and won't stay in. air supply to trailer hoses through valve is low on BOTH supply and service lines when knob held in. (there is low air coming thru BOTH hoses) Also has a air leak thru Park brake control valve when foot service brake applied with park brake applied any info would be appreciated. Quote Link to comment https://www.bigmacktrucks.com/topic/57188-ole-browny/ Share on other sites More sharing options...
carlotpilot Posted May 14, 2019 Share Posted May 14, 2019 kind of sounds like both the pp1 and pp7 valves need replaced. and checkthe out let hoses for mud dobber gunk Quote Link to comment https://www.bigmacktrucks.com/topic/57188-ole-browny/#findComment-422734 Share on other sites More sharing options...
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