fredhgross

On Board Compressed Air System

19 posts in this topic

We are new coach owners and are gathering equipment necessary to perform routine maintenance.

Question: Is it permissible to use my coach's air brake compressed air system to top off tire pressure?

Fredhgross

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Hi Fred,

Welcome to FMCA !

There is a convenience air connection on many of the coaches, so list the make of your chassis and coach manufacturer for the group.

There is always a catch 22 though. Some of those connections have a limited air pressure of 65lbs. because of a PPV(preset pressure valve) between the 120lb. tank and the connection.

Rich.

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Mine has a connection in front for air hose and the rear for toad brakes. Was going to equip with air hose for the tires but now maybe I should check if air is limited to that outlet.

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As suggested, check with your chassis maker/coach maker for the location of the air chuck and if possible, find out the "style" of the chuck (there are three different styles of connectors. Or just stop by an auto parts house and match up connectors to the chuck. If no chuck, there may be a plenum with block-off plugs where you can easily install an air chuck.

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On our 98 Windsor we had an air chuck in the front by the Gen Set. I checked it once and found no pressure. I was told that it was a connection for when you have to have the coach towed and the wrecker can connect the coach to the wrecker the same as we do our Toad. Any thoughts out there, true/false?

Herman

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Herman,

Very unusual for the one mounted on the front to not have pressure. If there was check valve in the line, then it would be for maintaining pressure in the coach system by feeding air from the tow truck. So I say False.

One does not want the pressure to drop to a point where the park brakes come on.

Without a check valve in the connection at the front one could use it for an air source and still reverse feed the air tanks to maintain at least 65lbs. of air in the system. If your 98 coach was setup that way, its was setup very different them most.

My set up allows for air to be pumped into the system at a point on the air dryer and that point could be adapted to a high pressure supply point.

Rich.

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Ray, you have been around air brake systems for some time. So I think with your skill sets, a high pressure feed could be introduced into the high pressure feed so it could be used for airing up the larger tires.

A 1/4in. line would be a little limiting to flow rate, but a lot easier to run then larger lines in most cases. Then equipped with an adjustable regulator would make it very handy indeed.

Most coach air pumps have a capacity of 15 to 18 CFM.

Not something I would suggest for those not real familiar with air system setups though.

Rich.

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New to the wonderful world of diesel...

Our new-to-us '04 Fleetwood Revolution 40C (Cummins 8.3 ISC on Freightliner XCR) has an air chuck attached to a manifold in the frontmost left outside cabinet. I haven't yet checked to see what sort of pressure is available there. The dealer suggested that the purpose of this connection was to add air to the system if needed for towing if the coach were disabled, and not as a source of compressed air for, say, inflating tires. However, the Freightliner manual specifically says, "air the suspension through the Schrader valve on the air dryer." So I guess I'll have to check the air chuck to see if it will deliver enough pressure for tires and if not, carry my little auxiliary compressor.

The manual also states that "Freightliner neither recommends nor approves tapping into the vehicle air brake system nor operating a towed vehicle ... by means of the vehicle braking system." Just sayin'.

--Tim

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I have a air outlet in the driver side front electrical department.There is also a shut off valve under the fender well right where the device is plumbed through the compartment so be aware.

One problem I have found is if you need more than 105 lbs force its snail pace slow and after 110 forget it.

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Herman, yes the fitting in front of your motor home is for towing. The tow driver can hook up air to air your motor home for towing. I have a 1999 Dynasty and it has a air chuck in the front left compartment for use to air up things like tires. It will go to 120 lbs if needed.

I have never seen one with a regulator so most will go to the set pressure of the compressor.

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Just bought a 150 PSI compressor from Amazon shipped to my RV site 110 bucks......got too many tires to worry about gas stations or online systems,,,,,,car tires/motorcycle tires....(both on trailer) trailer tires and of course bus tires.....

Seems like the best way to go.....for me anyway.

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I find the on board air supply to not have sufficient pressure and that the hose connection is not as easy to use as the small contractor air compressor I carry. Just my preference.

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The main problem with using the onboard compressor is it doesn’t start till the pressure drops to about 80-85 pounds. If you are trying to put more than that in-- say trying to get to 105 you will be letting air out of the tire if the tank pressure is lower. The way to get around this is to go pump the brakes till the pressure drops and the compressor kicks in. When your gage gets to more than what is in the tire you can add air. This works till the pressure again drops below what is in the tire and you have to repeat the process. I did see a nifty little tool on You Tube to make this easier. They made one with a gage to show the pressure in the line and when it got to low there is a valve to release air until the compressor kicks in. This saves running back and forth to check the line pressure and to bleed it down to start the compressor.

I am looking for parts to build one for myself. I did make a fitting to add air to the system with out starting the engine, like they do when towing. As it was mentioned there are several kinds of air fittings. The coach takes an “automotive style” fitting. Most air chucks you run into are “industrial type” These are the ones on your air compressor and air tools.

I built an adapter to go from auto to industrial. I also safety wired a spare air fitting to the air line just incase I ever need one and the tow truck doesn’t have one. I have looked at several coaches and they had one in that location.

Bill

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I use the onboard air tap to top off my tires all the time, when needed. Carry 110 in the front tires, and tops off with no problem. I wouldn't want to start from zero pressure to fill a tire, but works fine for daily maintenance. I carry a small portable for the car, bicycle, etc.

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I had the same concerns and just picked up a small compressor for $150 from Northern Tool that has a 150lb pressure setting.

Most compressors stop at 120lb so I think getting to 110lbs would be much slower.

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Tried using the onboard air on my old front tires (they took 120 psi). After an hour of trying I gave up and used another small compressor. Then I bought a Coleman 120 V tank unit. Works fine and I don't have to run the 435 hp main engine to do it.

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Hi Deen,

I'm surprised you're running that much pressure in your front tires. Is that what the tire manufacturers chart indicates for the load you're carrying or are you going off the manufacturers sticker? You may be rattling you and your passengers teeth for no good reason.

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Herman, yes the fitting in front of your motor home is for towing. The tow driver can hook up air to air your motor home for towing. I have a 1999 Dynasty and it has a air chuck in the front left compartment for use to air up things like tires. It will go to 120 lbs if needed.

I have never seen one with a regulator so most will go to the set pressure of the compressor.

On the side raidiator Monaco coaches the air governor is generaly located on the passenger side rear frame, a little deal withg 3 small air lines going to it with a plastic cap that looks like a mex hat on the adjustment screw turn the screw CC wise to increase the pressure or Clock wise to decrease, I have my governor set at 120 psi but a lot of folks like 130 psi and you can safely do that on a Monaco coach and dont see why not on the other chasses it would depend on the set pressure of the relief valve or better known a the pressure sensing valve.

A U tube explaning the air Governor.

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