mickwoodie

Sounds like youve had some pretty interesting advice on charging your ac system. if you want to simply check your system, grab the vapour line out of your evaporator with the engine running and the air con off. have someone turn the ac on and feel for the pipe to go cold, will take upto 15 seconds. (should drop to about 5-7 deg celcius, about the temp of a good cold beer). if it goes colder than this or starts to ice up then could be a problem. probably not an over gassing situation tho. more likiely if your compressor clutch is not kicking out it could be a thermostat issue at the evaporator (should be located under the dash on the cab side of the evaporator). in all honesty tho if the system isnot iceing up when your using it and is keeping the cab nice a cool then dont worry about it. its doing its job.

Thanks for the schmatic mate. dont think i explained the problem properly. when the park brake is released the service brake air system pressure drops off (using about 1/3 of the avalible pressure). the park pressure gauge does not drop away as if the system is feeding from the wrong tank. this dosent seem right to me? the brake system hasnt been worked on recently so theres no chance of any lines being crosed over. it could still be some simple fault, i havent worked on on highway trucks since my appretiship many years ago so could be overlooking something simple. cheers for your help.

Hey guys, ive got a late modle metro liner that seems to have abit of an air issue. when the park brake is released it drops the service brake air pressure. im thinking the only spot the two air systems cross over is in the priority valve in the bottom of the air drier? any ideas?