Community Forums

denochs · 10-10-2011, 01:50 PM

Has anyone had the problem with the "Low Air Pressure PSI" light coming on along with the alarm horn? The air bags are up and holding air. Brakes are working fine. Doesn't loose air while sitting with engine off either.

Drove it 20 miles to fuel up and had no problems other than the annoying horne going off constantly.

Could not find a fuse in the step well fuse blocks either.

HELP!!

Dave

denochs · 10-10-2011, 02:17 PM

Will be off line until tomorrow morning. Hopefully, someone comes up with an answer.

Dave

LA-HODAG · 10-10-2011, 05:52 PM

What are your air gauges showing? Unless they show 90 lbs or more in both tanks you should really think twice about driving it. The suspension staying up is not a reliable indicator of a properly functioning air system. Since you were able to release the parking brake you may have sufficient air and just a sensor failure, but the gauges should tell the story. If your gauges read low you should check around the coach while it is running and listen for air escaping. If there is a major leak in the system or a valve is stuck open, you can usually hear it unless it is in the engine compartment. On a prior coach I had a valve stick open in the air dryer and I was unable to build up more than 40lbs of air in high idle. I could hear the air releasing from the dryer. Suggest you check those things and report back.

Fred Cooper · 10-10-2011, 11:11 PM

Sounds like the low air pressure sensor problem I had with my Freightliner chassis. Replaced the sensor and problem went away. On your chassis, I have no idea where the sensor would be located. The Freightliner has it on the frame rail, driver side, front of rear axle. Many Monaco's have the sensor on the bottom of the air brake knob assembly.
Fred

Craig_R · 10-11-2011, 12:54 AM

Quote:

Originally Posted by denochs

Doesn't loose air while sitting with engine off either.

Yes, but does it lose air while sitting with the engine off and the parking brake released? (Don't forget to chock your wheels.

)

When the parking brake is applied there is zero air going to the brake chambers. The parking brakes are applied by very heavy duty springs in each of the rear brake chambers. When you release the parking brake, air pressure is applied to one of the diaphragms inside each of the rear brake chambers causing the spring to compress and release the parking brakes. At that point the emergency side of the brake system is considered to be "charged" with air. If you have a leak in an emergency air line or a blown diaphragm in one of the rear emergency brake chambers it won't make itself evident until the parking brake is released.

Quote:

Originally Posted by denochs

Drove it 20 miles to fuel up and had no problems other than the annoying horne going off constantly.

Did you notice what the air pressure gauge(s) were reading during the trip?

denochs · 10-11-2011, 03:20 PM

Thanks all for the points to check. Also called American Coach tech support. They passed me to Spartan tech support. Spartan said it was AC instrumentation.

The air pressure indicators are holding air with and without the park brake set. Can't hear any leaks either. Pressure is maintained between 90-120.

I have tried all of your suggestions and come to the conclusion it is a sensor on the brake valve assembly. There are three of them. Tomorrow, I will take one of them off and go to a truck parts store here in Daytona. Will replace one at a time until I've tried all three.

Report back tomorrow. Thanks for the ideas.

Dave

Craig_R · 10-11-2011, 09:15 PM

It sounds like you're on the right track Dave. I hope all three sensors are the same part so that you can just keep changing them out until you find the bad one without having to run back and forth to the parts store to get different ones.

Good luck

denochs · 10-12-2011, 05:40 AM

Craig,

They look to be the same and are fairly easy to get to on the front firewall in the genny area.

Heading out now to start working on it.

Dave

denochs · 10-22-2011, 06:21 AM

RVing is such an adventure. Every corner opens the opportunity to climb a hill or decend a valley...

Finally found a new "air pressure sensor" at Lazy Days in the Lakeland FL area. Only a 40 minute drive. But waisted time and $25 for the part none the less. At least thus far.

Spartan (who finally took ownership of the airbrake assembly) now tells me there are two of the same sensors for the low air pressure warning. Finally located it on the inside of the firewall (the other three are on the outside with the air brake assembly) among what seems to be a thousand wiring harnesses. Can't even get a half inch wrench on it.

Spartan tech support said to check the air pressure at one of the supply lines going into the air brake assembly. If it is near what the instruments read he said it is likely the sensor I can't get to. If not, it is likely Fleetwood instrumentation problems.

Any other ideas??

Dave

Craig_R · 10-23-2011, 11:12 AM

Quote:

Originally Posted by denochs

RVing is such an adventure. Every corner opens the opportunity to climb a hill or decend a valley...

Finally found a new "air pressure sensor" at Lazy Days in the Lakeland FL area. Only a 40 minute drive. But waisted time and $25 for the part none the less. At least thus far.

Spartan (who finally took ownership of the airbrake assembly) now tells me there are two of the same sensors for the low air pressure warning. Finally located it on the inside of the firewall (the other three are on the outside with the air brake assembly) among what seems to be a thousand wiring harnesses. Can't even get a half inch wrench on it.

Spartan tech support said to check the air pressure at one of the supply lines going into the air brake assembly. If it is near what the instruments read he said it is likely the sensor I can't get to. If not, it is likely Fleetwood instrumentation problems.

Any other ideas??

Dave

This is starting to sound like one of those jobs for a very small ambidextrous contortionist who has a lot of patience.

All kidding aside Dave, I have no familiarity with the Spartan chassis, only air brake systems in the general sense. What Spartan is telling you sounds correct. You would be measuring a supply line which would essentially the same as measuring the pressure at the tank.

Now having said that, you could try testing the dash air pressure gauge (Fleetwood instrumentation) by using another gauge in it's place and if that reads properly then it would point to the inaccessible sensor. You would still have to change it out but at least you wouldn't have had to work at it quite as hard and be fairly confident that you were doing the right thing.

I hope that made sense.

denochs · 11-04-2011, 05:37 PM

Here we are almost two weeks later with the new sensor still in hand. Started the coach two days ago and the "low air pressure" light and warning horn went off as it used to about 15 seconds after startup. Tried it several times since then and everything seems to be working fine.

Conclusion? Maybe a piece of debris or moisture?? At any rate it was a learning experience. As it turns out the inaccessable sensor on the inside of the firewall was not the "low air pressure" sensor either. There are two of them on the inside of the firewall farther left (facing forward) that are even more inaccessable without taking the carpet up and the side panel where the tranny shift select is mounted.

If anyone has this problem on a Spartan chasis, the sensors are not visible. Once you remove the kick plate to the left of the steering column you can pull the sensor plug off (according to Spartan) to check if the sensor is bad. Depending on the type of sensor (this one is a NC/normally closed sensor) it should be easy to find out which one is bad by following this proceedure. If your sensor is a NO/normally open type you would have to put a jumper in the end of the connector after pulling it out to simulate it closing.

Hope this is some help to others that may experience this problem.

Dave