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Topic: 1998 U-320 Manual Air bag use (Read 804 times) previous topic - next topic

1998 U-320 Manual Air bag use

Hi,

I am getting ready to do rear brakes/air bags on my coach, but I am having issues getting the bags to inflate so I can get my safety blocks inserted.

I was able to get my front bags inflated and blocks inserted, but the rear will not come up manually. I have tried key on/key off, dump and refill, the raise button....  nothing is budging the rear bags. I took the front blocks out, lowered, refilled and now the bags won't go high enough for my blocks.

Also, I noticed that the valve under the water filter (next to the pump) blows air whenever the pump is running. I plugged it, but still nothing.

Is there something I am missing? 

Any insight is appreciated. 

Re: 1998 U-320 Manual Air bag use

Reply #1 –
Greetings!  Need more info.

Has your air system operated normally in the recent past?

Will the coach go to correct ride height with engine running?

Is this "failure to raise" a new problem?

Is the engine running or are you trying to use the HWH aux air compressor to raise the coach?

How much air pressure do you show on dash gauges when trying to raise coach?

Re: 1998 U-320 Manual Air bag use

Reply #2 –
Quote from: madmaxx –
Hi,

I am getting ready to do rear brakes/air bags on my coach, but I am having issues getting the bags to inflate so I can get my safety blocks inserted.

I was able to get my front bags inflated and blocks inserted, but the rear will not come up manually. I have tried key on/key off, dump and refill, the raise button....  nothing is budging the rear bags. I took the front blocks out, lowered, refilled and now the bags won't go high enough for my blocks.

Also, I noticed that the valve under the water filter (next to the pump) blows air whenever the pump is running. I plugged it, but still nothing.

Is there something I am missing? 

Any insight is appreciated. 
How much pressure do you have in your air tanks?  You might have to put engine on high idle or rev it up a bit to keep the pressure up.  The front on mine comes up faster....assume because it weighs less and rear on the down hill side (I am parked on a slope) comes up slowest.

Re: 1998 U-320 Manual Air bag use

Reply #3 –
Sounds like rear fill valves solenoids are non operational if the motor is running

Re: 1998 U-320 Manual Air bag use

Reply #4 –
The coach is new to me, but from the looks of it, the rear bags have been inoperable for some time due to the tire rubs on the top of the fenders.  After it runs for a while the green travel light will come on, but I don't think the rear bags are taking air.

I was using the 12v pump. I wasn't aware that I could raise it with the engine running. I will give that a go..  I checked all of the fuses and they are ok. If it won't raise of engine air, I must have a solenoid activation issue.

Re: 1998 U-320 Manual Air bag use

Reply #5 –
If you are trying to raise with only the hwh compressor, try having the engine running and then it should get the bags inflated enough. If you have someone to help you have then push the raise button while you install the blocks otherwise hold the raise with the engine running after the air pressure reaches 125 hold the raise a little longer then turn off the engine before releasing the raise button.

Re: 1998 U-320 Manual Air bag use

Reply #6 –
Quote from: madmaxx –
I was using the 12v pump. I wasn't aware that I could raise it with the engine running. I will give that a go.

It will be very difficult for the 12v aux compressor to raise the rear of the coach.  Its output is more to make small adjustments and maintain level once parked (and keep slide bladders inflated when parked if you have slides). 

For any significant raising, especially of the rear, you should have the coach engine running to use the engine-powered compressor.

Re: 1998 U-320 Manual Air bag use

Reply #7 –
It worked!!! It is up and on the blocks.  I definitely have an air leak on the rear. One of the lines coming from the air tank that's next to the solenoid block is chattering from a leak. I tried to track it into the cable tray, but it disappears. Gonna have to hit the schematic.

Thanks for the input!!  I have learned something about the coach.  Much appreciated!!!!

Re: 1998 U-320 Manual Air bag use

Reply #8 –
Quote from: madmaxx –
The coach is new to me, but from the looks of it, the rear bags have been inoperable for some time due to the tire rubs on the top of the fenders.  After it runs for a while the green travel light will come on, but I don't think the rear bags are taking air.

I was using the 12v pump. I wasn't aware that I could raise it with the engine running. I will give that a go..  I checked all of the fuses and they are ok. If it won't raise of engine air, I must have a solenoid activation issue.
Evidence of tire rubbing does not necessarily mean the air bags are not working.  Could mean the shocks are bad or somebody moved the coach without waiting for it to raise up to the proper level.

Like other suggested, try it with the engine running and watch your air pressure.  Wait until the tanks are pretty full before you start raising the coach, then keep the RPMs up some when you start raising the coach and monitor the air pressure. 

Unless you have a helper to install the safety blocks, do like Redtractor said and turn the engine off to prevent the coach from returning to travel height.....I rarely have an extra set of hands, so that is what I have to do. 

Re: 1998 U-320 Manual Air bag use

Reply #9 –
Another way to raise is to connect an air compressor to your exterior air fitting (the one that's used to air the coach for a tow). Here's a photo of mine. This rig (97 270) had one in the wet bay compartment and on the other side, same compartment. You don't need the gauge.

Re tire rubbing, most of these old rigs will show some. Due to a bad design, the body will lower right onto the tires.
jor

Re: 1998 U-320 Manual Air bag use

Reply #10 –
I find that when I raise my coach the air pressure drops, I keep pushing the button until the air pressure is back up to 120 psi and
then I turn the engine off and then let go of the the raise button.  It takes a few minutes to raise the coach. My coach will stay up
for days.

Re: 1998 U-320 Manual Air bag use

Reply #11 –
When I park, I let the air out then level

Re: 1998 U-320 Manual Air bag use

Reply #12 –
Quote from: Nigel0434 –
When I park, I let the air out then level

Why?  That's more work for the system than simply lowering the high parts (unless of course you want to start with the entry step as low as possible).

ETA I know other brands which use air for OTR and jacks when parked have you dump the air then level (because the airbags aren't used when parked), but FT's with air leveling are a bit of a different animal.

Re: 1998 U-320 Manual Air bag use

Reply #13 –
I have 2 air gauges on the dash. The upper gauge will go up to 140 psi, the lower gauge will only get to about 115 psi.  I assumed the top gauge is the front system and the bottom gauge is the rear system.

When I looked at the schematic, one gauge is tied to the "front brake left tank" and the other gauge is tied to the "front brake left tank" and the "rear brake right tank".  However, it looks like the one that is "connected" to both is connected to a line that's feeds a check valve which feeds air to the parking brake from both tanks.

Would one of you guys know what these gauges are reading from this system?

Re: 1998 U-320 Manual Air bag use

Reply #14 –
If you take a can of black spray paint and cover the rub area you will know if it is actually rubbing or just a one time event. I have prior rub marks on all four corners. Cheap tell tail indicator.
Scott

Re: 1998 U-320 Manual Air bag use

Reply #15 –
Quote from: jor –
Another way to raise is to connect an air compressor to your exterior air fitting (the one that's used to air the coach for a tow). Here's a photo of mine. This rig (97 270) had one in the wet bay compartment and on the other side, same compartment. You don't need the gauge.

Re tire rubbing, most of these old rigs will show some. Due to a bad design, the body will lower right onto the tires.
jor

Never have noticed this "exterior air fitting". Do all coaches have one...two?  Where to look?  Our 34' is one year newer than JOR but not located in same place.

Re: 1998 U-320 Manual Air bag use

Reply #16 –
Look near the top in your propane compartment.
 

Re: 1998 U-320 Manual Air bag use

Reply #17 –
Quote from: madmaxx –
I have 2 air gauges on the dash. The upper gauge will go up to 140 psi, the lower gauge will only get to about 115 psi.  I assumed the top gauge is the front system and the bottom gauge is the rear system.

When I looked at the schematic, one gauge is tied to the "front brake left tank" and the other gauge is tied to the "front brake left tank" and the "rear brake right tank".  However, it looks like the one that is "connected" to both is connected to a line that's feeds a check valve which feeds air to the parking brake from both tanks.

Would one of you guys know what these gauges are reading from this system?
I pulled up the air schematic for U320 from our Forum Library.  If this is the same as your drawing, then I don't understand your question.  The air lines from the two brake tanks (mounted in front end of coach) are clearly marked.  They both go directly to the PIE (Pressure Interface Module) without taking any detours.  Do not be confused by air lines which (on the schematic) cross, but do not interconnect.  Actual interconnections are marked by a little circle or half circle symbol.

https://www.foreforums.com/index.php?action=media;sa=media;in=3301

As to which dash gauge is "Front" and which is "Rear" I can't answer that.  They are electronic - no air line to trace.  Your Owners Manual should tell you which is which, unless it was written by a idiot.

At the exact time that your engine air compressor unloads (the dryer purges) both dash air gauges should read the same pressure.  If they do not, then there is a malfunction somewhere in the system.  Since 140psi is higher then normal, and 115psi is lower than normal, I suspect the PIE may be failing.  This is not uncommon.  Search the Forum for pertinent info.  Here is one link to get you started:

Rear air pressure gauge