Draining Air Tanks

[OneRVer]

Hello all, I have three air tanks on my Freightliner chassis. Each have their own drain valve. I have drain all three tanks and my red needle has dropped to 0 psi but my green needle is staying at 60 psi.

What am I missing?

[Gary RVRoamer]

Since this is a Freightliner question and your Triple E is not a Fleetwood product anyway, I moved it to the Freightliner Forum (was in Fleetwood).

My Freightliner doesn't have red and green needles - just front and rear air gauges. Does your red and green correspond to my front and rear air tanks? The front tank has two chambers, hence two drain valves.

[bdpreece]

Try turning the ignition key on and see if the reading on the green drops.

[OneRVer]

Sorry, I missed read the forum. Thank you for moving it.

[OneRVer]

Quote:

Originally Posted by Gary RVRoamer Since this is a Freightliner question and your Triple E is not a Fleetwood product anyway, I moved it to the Freightliner Forum (was in Fleetwood). My Freightliner doesn't have red and green needles - just front and rear air gauges. Does your red and green correspond to my front and rear air tanks? The front tank has two chambers, hence two drain valves.

The red needle is the rear, the green is the front. My gauges are not electrical. I have airlines going straight to the gauge.

[bdpreece]

Gauge may be stuck. Remove the line from the back of gauge and see if it drops.

[Gary RVRoamer]

The front tank supplies the air brakes and 60 psi is about the minimum pressure needed for the brake. I wonder if the system is valved to retain that much pressure even with the drain valves open. The system is usually protected to prevent air loss in the suspension from fully draining the brake air chamber.

[OneRVer]

Quote:

Originally Posted by Gary RVRoamer The front tank supplies the air brakes and 60 psi is about the minimum pressure needed for the brake. I wonder if the system is valved to retain that much pressure even with the drain valves open. The system is usually protected to prevent air loss in the suspension from fully draining the brake air chamber.

Very good point. I was going to remove the air line from the gauge but that would not answer my question. Accept I would know if the needle is stuck or not.

Thank you for all of your replies. When I know for sure I will post back.

[bdpreece]

Since you need to be able to drain off all the air pressure in order to be able to service the air system I doubt that it is designed to hold air pressure no matter what. I thought your question was why does your gauge still show 60 pounds. Probably because the gauge is faulty if you really held the release lines until all the air has escaped.