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zzjea · 06-05-2014, 08:56 PM

We are camping right now and I noticed from my TPMS that the inside dual on one side was about 8# lower than the other tires. So I hooked up the air hose from the front connection with the engine running and tried to air it up but it would not fill the tire but had air in the hose. So I checked the dash guages and they never got to full capacity. The jacks are down and the pop off valve on the air system never went off after at least 10 min. of engine running.

Is there something preventing the air system to fully function if the jacks are down? We are level now and I would like to keep the jacks down as we will be here for a few more days. I never had this issue when the tires are down and the jacks are up.

Any ideas what might be happening?

I will try to get a stand alone compressor to fill the tire in the meantime.

John

luckyd · 06-05-2014, 08:59 PM

Normally your onboard air system will only go to 90 psi.
If you are looking for more you will need a compressor.

RickO · 06-05-2014, 09:06 PM

Quote:

Originally Posted by luckyd

Normally your onboard air system will only go to 90 psi.
If you are looking for more you will need a compressor.

Hmmm.... Do you mean for his particular National DP or for DPs in general. I think it's common for on board compressors to exceed 90 psi. Mine cuts off at 120#... But with the cycling of the compressor, it can take some doing to get those last few pounds into the tire.

I don't know about the impact the jacks being down impacts this particular unit but some of our experts will be along soon to help out I'm sure.

Good luck

Rick

zzjea · 06-05-2014, 09:13 PM

Quote:

Originally Posted by luckyd

Normally your onboard air system will only go to 90 psi.
If you are looking for more you will need a compressor.

My dash gauges (front air and rear air) normally show 125# when engine is running and about 100# when sitting for a day or more. Is this pressure different than that which goes thru the air hose system from one of the tanks?

RickO · 06-05-2014, 09:33 PM

Quote:

Originally Posted by zzjea

My dash gauges (front air and rear air) normally show 125# when engine is running and about 100# when sitting for a day or more. Is this pressure different than that which goes thru the air hose system from one of the tanks?

No. It's the same, but once you begin to inflate a tire to ~100# or so the tank quickly looses that high pressure and the compressor needs to cycle again. This can be time consuming but it does eventually work.

Rick

zzjea · 06-06-2014, 01:57 PM

I aired up the tires with a portable compressor. I still could not get the air gauges on the dash to come all the way up while on the jacks. Hope all works properly when I lower the jacks when we leave in a few days.

John

zzjea · 06-07-2014, 04:44 PM

Well, I raised the jacks and the gauges still would not come up to 125# and stayed at 100#. I ran the rear duals driver side onto some boards to raise the coach a little on that side. Later I started the engine and the right front ride height valve started dumping air like there was no valve. So I called a mobile RV tech and they came out a few hours later.

Well, they could not find a problem and the dash gauges came up to 125#. Go figure. Everything seems to work now that the coach is on the ground for a while. He said that with the jacks down and the axles up but drooping, the ride height valves would dump air thinking that it was too high. Had not thought about that but makes sense.

Cost me $75 but we have more peace of mind now especially the DW and you know what happens if the DW is not happy.....

Another strange thing happened today or sometime since we left last Sunday.

The front windshields shifted about over an inch toward the driver's side at the top and left a gap on each side. I discovered this as I was washing some tree grime off the roof and cleaned the front windshield. I think it will stay in place until I get home and get a glass place to reseal it. I will put tape over the gap until we get home to keep water out. Can't help but think it is related to the air pressure and ride height issues.

John