Supply air - Printable Version
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+--- Thread: Supply air (/showthread.php?tid=2534)
RE: Supply air - dannymarilyn - 09-27-2015
(09-26-2015, 09:33 PM)ccjohnson Wrote: I think Richard may be on the right track. Perhaps a stuck PPV is not letting air into the supply system. Not exactly sure where it is located though.OK, I give, what is the PPV?
Danny
RE: Supply air - Richard - 09-27-2015
Pressure Protection Valve. It is a valve that will let air pass slowly but not quickly. So if something catastrophic happens in the supply loops, the valve will not allow the air in the brake system to whoosh out and leave you without the air to stop the coach.
RE: Supply air - Richard - 09-27-2015
Danny, see 77Newell's (Jon) post to start looking for the quarter turn isolation valves.
Mine, on a later model coach are above the rear axle of the coach, between the chassis rails. You need six foot long arms to reach them while laying under the coach. Hah.
Since classic problem solving would seem to connect this event with the coolant change, have you spoken with the technician who did the work to see if he remembers turning any valves?
RE: Supply air - 77newell - 09-28-2015
To clarify Richard's description of the PPV at least as it applies to the one on my coach. The PPV allows flow through the valve whenever the inlet pressure is above a certain value, on my coach it is set at about 67psi. On our coaches it allows air to be used for non-airbrake uses only when above its set point. Therefore, as Richard described, helping to keep the brakes operating normally should an air leak larger than your compressor can make up occur in the non-airbrake parts of the coach compressed air system. If the PPV were not in place, a rupture in the supply line to the 6-pack for example would leak air fast enough that the pressure in the air brake system would drop to the point that your emergency/parking brakes would automatically engage. The PPV prevents that from happening.
RE: Supply air - dannymarilyn - 09-28-2015
(09-28-2015, 06:24 AM)77newell Wrote: To clarify Richard's description of the PPV at least as it applies to the one on my coach. The PPV allows flow through the valve whenever the inlet pressure is above a certain value, on my coach it is set at about 67psi. On our coaches it allows air to be used for non-airbrake uses only when above its set point. Therefore, as Richard described, helping to keep the brakes operating normally should an air leak larger than your compressor can make up occur in the non-airbrake parts of the coach compressed air system. If the PPV were not in place, a rupture in the supply line to the 6-pack for example would leak air fast enough that the pressure in the air brake system would drop to the point that your emergency/parking brakes would automatically engage. The PPV prevents that from happening.
Thanks! That sounds like a candidate for the culprit.
RE: Supply air - dannymarilyn - 09-28-2015
Mechanic pulled manifold with isolation valves (we think maybe?) with some kind of regulator on it. No air flow?
Could this be the supply air problem?
Thanks!
Danny
RE: Supply air - 77newell - 09-29-2015
Danny: couldn't get images to load so I can't tell
RE: Supply air - Ozarkguy - 09-29-2015
77newellDanny: couldn't get images to load so I can't tell
RE: Supply air - Richard - 09-29-2015
No air to the manifold, or no air through the picture that Jimmy attached?
That picture is indeed what we are talking about. In the picture the valves are closed. Is that how they were found? They should be open.
RE: Supply air - 77newell - 10-01-2015
Danny: that picture shows what I have in my 93. The first item on the left is the pressure switch for the low air pressure warning light on the dash. The second item on the left is the PPV. It should pass air once the pressure on the left (inlet from air tank) exceeds 65-75psi, will be closed until then.
Richard is correct in that the two valves need to be open when operating the coach normally.