BAC Forum

General Boards => Technical Support => Topic started by: Forrest King on November 07, 2019, 12:06:04 PM

Title: air gauge
Post by: Forrest King on November 07, 2019, 12:06:04 PM
what do the red an green needles on air gage mean. my green gage bleeds down over night. where should i start looking for a leak?
Title: Re: air gauge
Post by: Mike Shumack on November 07, 2019, 01:00:30 PM
The air system has a "Primary" and "Secondary" side/system. That is done so if air is lost to one "side" (like a hose blows) you will still be able to brake with the air in the other side. The different needles (or gauges, if you have two) will display the air pressure for each side. Usually the Green is the "Primary" side which is rear brakes.

Here's a basic diagram of how it looks (the different color line represent the different sides).

Title: Re: air gauge
Post by: Fred Brooks on November 07, 2019, 01:08:41 PM
   Forrest, the red and green needles on your air gauge represent the air pressure in your primary and secondary air tanks. The red needle is your rear air brakes only. It will move only when the brakes are applied. The green needle is your secondary air tank which is your front brakes, air ride suspension, horn and other accessories, When driving, you will see the green needle go from 120psi down to 90psi and then back up to 120psi. As you drive the coach is constantly leveling itself so it uses air to do that. When the air pressure gets down to 90psi the air compressor on the engine comes on and builds pressure back up to 120psi and you hear the reciever/dryer cycle and purge contaminants from the compressor and dryer.
   Safety system works this way, If the coach has an issue with the air compressor or you start losing air pressure for what ever the issue, you get a warning buzzer and light to alert you at about 70 to 80psi. If this happens, find a place to pull off the road safely. If you don't, when the air pressure gets down to 40psi it starts to apply the park brake. Now you will come to a stop on the road. Turn on your flashers, exit the coach and get away from it. Fred
Title: Re: air gauge
Post by: Jason Worman on November 08, 2019, 04:07:10 PM

Just a follow up question. So my air gauges while parked will slowly decrease, within about two weeks the needles drop to zero. Should I run the engine to air up the system?

Thank you
Jason Worman
Title: Re: air gauge
Post by: Fred Brooks on November 08, 2019, 06:25:22 PM
  Jason, nope. 2 weeks is above normal time. May want to level her if you have hydraulic jacks if you like. Fred