amata1957 Report post Posted July 28, 2020 Took my recently acquired 1999 Foretravel for a short trip to Fort Davis Texas from Odessa Texas. We camped out for three nights and had a great time getting out on the road. On the way back I noticed the air gauge kept dropping to 95 psi and up to 110 psi. It repeated that all the way home. Never going over 110 and never dropping under 95. Not sure if I should be concern or is this normal?.thanks for any feedback. Share this post Link to post Share on other sites
wildebill308 Report post Posted July 28, 2020 Yes, it is normal for your air preshure to varrey. The question is how fast does it change? Does it drop fairly rapidly when you are just sitting with the engine running? Bill Share this post Link to post Share on other sites
jleamont Report post Posted July 28, 2020 Are you referring to the dash mounted air pressure gauge? If so that is for the entire air system, not just the air bags. It shouldn't move while driving without stepping on the brake pedal. Does it pass the air brake system test? Here is an example of a standard test; I would perform these steps and report back your findings to help narrow down what system (if any) is at fault. Test Air Leakage Rate (Static check) With a fully-charged air system (typically 120 psi), turn off the engine, chock the wheels, release (push in) the parking brake button (all vehicles) and time the air pressure drop. After the initial pressure drop, the loss rate should be no more than 2 psi in one minute for single vehicles. Test Air Brake System for Leaks With parking brake, (all vehicles) and trailer air supply button (for combination vehicles) released (pushed in), apply firm pressure to the service brake pedal. Watch the air supply gauge and listen for leaks. After the initial pressure drop, the loss rate for single vehicles should be no more than 3 psi in one minute. If the air loss rate exceeds these figures, have the air system repaired before operating. Test Low Pressure Warning Alarm and/or Signal Turn the key to the on position. Rapidly apply and release the service brake pedal to reduce air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 60 psi in the air tank. If the warning alarm/signal doesn’t work, you could be losing air pressure without knowing it. This could cause the spring brakes to activate suddenly. Only limited braking can be done before the spring brakes come on. Check That the Spring Brakes Come on Automatically. Continue to rapidly apply and release the service brake pedal to further reduce air tank pressure. The parking brake button should pop out when the air pressure falls to the manufacturer’s specification (usually between 20 to 40 psi). This causes the spring brakes to come on. Share this post Link to post Share on other sites
amata1957 Report post Posted July 28, 2020 Yes I am referring to the dash gages . It was going up and down while on the highway and not pressing on brakes.It would hold at 110 for a few seconds then drop to 95, hold for a few seconds and go up again to 110. Thanks for the info on the brake system test. I will try that, Share this post Link to post Share on other sites
richard5933 Report post Posted July 29, 2020 Probably worth having the system checked out. Sounds like you may have a leak in the air system somewhere - could be in the braking system or it could be in the suspension system. Pressure shouldn't drop that quickly. Also, check your manual for the correct cutout pressure on your compressor. Many modern systems will go to about 120-125 before cutting out, so unless yours is an older system designed for a lower pressure you may need a new compressor governor as well. BIG WARNING!!! Before you get under the coach to check for leaks, you need to make certain that the coach is properly supported. One wrong move, one single component failure, or one airline bumped loose and the coach can fall on you. There is not room to live under a coach that falls. The leveling jacks are not intended to support the coach while you're under it. Check the manual for the proper support spots on your coach's chassis and do your homework on proper blocking so you stay safe. Remember - you're not supporting the axles here - you need to support the body so that it doesn't fall on you. Share this post Link to post Share on other sites
rayin Report post Posted July 30, 2020 (edited) How long since the air dryer has been serviced? If the desiccant air dryer filter is bad, and/or purge valve is bad, strange things happen to air pressure.This can cause the air compressor to fail due to exceeding the duty cycle. Edited July 30, 2020 by RayIN Share this post Link to post Share on other sites
