Air Gauge Needle Question...Green vs Orange

leedowney · 03-07-2010, 07:03 PM

Hey guys. A few quick questions. On my 2000 Journey, there are two air gauge needles. One is green and the other is an orange color. What do these two different color needles represent? I know they show air pressure. They build to around 125 psi then the check valve cuts the pump off. After a few braking stops and a few changes in the road, both needles seem to descend at the same rate. Once they drop to around 105 psi, the pump kicks back on and returns both needles to 125 psi. Is this normal or should the pressure remain at 125? Does this indicate an air leak. I have crawed underneath and with soapy water spray, checked all my valved for leaks and there are none.

Any issues or is this normal?

Thanks.

ernieh · 03-07-2010, 07:31 PM

One is for the primary (rear) and one is for the secondary (front) air tanks. As I recall the max allowable air loss is about 3 lbs. per minute. If you set and release the parking brake several times, you will know which is which.

Hooligan · 03-07-2010, 08:42 PM

leedowney: What you describe is normal, the system should build to 125-130 lbs then cutoff. As pressure drops, the compressor should kick in again by about 85 lbs.
The Air Brake system should be checked before a trip, to be sure it is working correctly. Here is the check procedure.
Motorhome air brake system testing
Always do the check after any work on the system.

It only takes a few minutes. It is important that the parking brake is off before applying heavy pressure to the foot brake or you can damage the system. (wheels chocked)
If pressure drops below +- 45psi, while driving, the rear brakes will come on hard and stay on ..
hope this helps

J Walker · 03-08-2010, 07:53 AM

Mine go up close to 130 psi on the gauges and stay there. I was a little concerned that the compressor was on all the time but Freightliner gave me some assurance that my operation was ok. I have read that others get a range of pressures between cut-on and cut-off.

Stillwater · 03-08-2010, 08:13 AM

It is not possible to have an air system reach 130lbs and stay there. They do not work that way. They fluctuate between 85 min and 130 max. How often do you look at your gauge? If your compressor stayed on all the time then a safety valve will release at 150 lbs. If that failed a compressor is capable of pumping up to 300-400 lbs.or more. Before that happened probably a hose or valve would let go.

leedowney · 03-08-2010, 10:01 AM

Just to put my mind at ease, I just called Freightliner. The tech told me my air system is working just as it should. He said all the tests I've done indicate things are normal. He said, depending on how rough the road I was on and how many times I hit the brakes would result in how quickly those needles drop. He said with the coach just sitting, I should not lose more than 5 lbs of air in 2 minutes. He said the green needle is for the rear tank and the orange needle represents the front tanks. They should always line up on top of each other unless you have an air leak.

Thanks guys for the input. I can rest easy knowing my air system is functioning correctly.

I did ask the tech about J Walkers comment about his pressure going to 130 psi and staying there. He said if the coach was moving, that would seem impossible. The air is escaping as the brakes are being depressed and the air ride is leveling out as you travel down the road.

**Gary RVRoamer** · 03-08-2010, 06:52 PM

Mine doesn't vary much from 125 unless I am actively using the brakes (rare, since the engine brake does a lot of the work). I think my compressor kicks in at about 100 psi too. I've never seen the gauge drop to 85 unless I am dumping air to level the coach when parked.

FWIW, I have two separate gauges for front and rear tanks. I think the gauge configuration is coach-specific and not a Freightliner thing. The coach builder supplies the dashboard.