How Do I Operate Tag Axle Suspension?

Topic: How Do I Operate Tag Axle Suspension? (Read 2252 times) previous topic - next topic

How Do I Operate Tag Axle Suspension?

May 16, 2017, 02:09:29 am

Hello All,

So one of my Reno list items for my new '86 Grand Villa 3300 GVF SBI is to figure out how to work the Air Suspension for the tag axle.

Right now the air pressure gauges on the dash reads 0 PSI. The manual says I shouldn't drive it with less than 3PSI.

The only problem is the two switches on the dash don't appear to do anything and I can't find anything in the manual about it's operation.

Under the left side of the coach, one of the storage bays has an air pressure hose. I assume that goes to whatever air pressure tank is used to fill the Air Bags for the Tag Axle.

But I've found no switches for the Air Hose either.

Nothing that would indicate how to turn on the Air Pressure system to either fill or lower the Tag Axles or use the air hose.

Any ideas? Does the engine need to be on? Does the generator need to be on? Where should I look for the on switch for the air system? Do the left and right "Raise/Lower" Switches for the tag axles control everything? If so, how do I work them?

Sorry for all the newby questions. Thanks!

Also, let me know if pictures of anything would be helpful.

Re: How Do I Operate Tag Axle Suspension?

Reply #1 – May 16, 2017, 08:19:40 am

Quote from: AKATheAlchemist – May 16, 2017, 02:09:29 am

Also, let me know if pictures of anything would be helpful.

Photos are ALWAYS helpful when you ask questions. Worth a thousand words, as they say.

You have a less common chassis, and there will not be as many members available with first-hand knowledge of your particular systems. BUT, we have some really smart people on this Forum, and once they SEE what you are working on, they will probably be able to figure it out!

Re: How Do I Operate Tag Axle Suspension?

Reply #2 – May 16, 2017, 08:40:45 am

Follow the air hose and see if it leads to the compressor and lines to the tag bags. I will bet that someplace on the dash there are switches that allow the bags to be filled. If you find little solenoids in the hoses, clean up the wires and maybe remove any tie tape wrap and see if any of the color is still there. If you get lucky the wires will appear under the dash .
Next step is to make a 40ft test lead and test light .. I stick my( 2bulb ) test light under a wiper blade and start checking for continuity at the dash . Batterys off.

Re: How Do I Operate Tag Axle Suspension?

Reply #3 – May 16, 2017, 06:33:22 pm

Okay I added pictures to the original post. couldn't figure out how to add them to a reply.

First pic is Driver side air bag. looks okay.

Second pic is passenger side air bag. Looks badly busted.

Third pic is the dash controls.

Fourth and fifth pics are the instructions from the manual

sixth pic is of what I assume is the air pressure tank. Though I'm not sure on that.

Re: How Do I Operate Tag Axle Suspension?

Reply #4 – May 16, 2017, 06:37:07 pm

Quote from: AKATheAlchemist – May 16, 2017, 06:33:22 pm

Okay I added pictures to the original post. couldn't figure out how to add them to a reply.

Either use "Preview Post" at the bottom when creating a new post, which puts you into the full editor, or (globally) change your profile to not use the quick editor (I think it's in "Look and Layout".

Re: How Do I Operate Tag Axle Suspension?

Reply #5 – May 16, 2017, 07:07:02 pm

Quote from: Michelle – May 16, 2017, 06:37:07 pm

Either use "Preview Post" at the bottom when creating a new post, which puts you into the full editor...

Thanks!

Re: How Do I Operate Tag Axle Suspension?

Reply #6 – May 16, 2017, 07:08:18 pm

Okay so in this post:
air bag replacement parts info

I found a discussion on replacing the airbags. They mentioned these were a good fit for replacing the airbags in the coaches that have air suspension all around. Would they word for my tag axle? I have leaf springs everywhere else.

AS9448 by CONTITECH - CONTITECH AIR SPRING 64286/1R11-150/8563

Re: How Do I Operate Tag Axle Suspension?

Reply #7 – May 16, 2017, 07:15:16 pm

Quote from: AKATheAlchemist – May 16, 2017, 06:33:22 pm

sixth pic is of what I assume is the air pressure tank. Though I'm not sure on that.

It would REALLY be helpful if you had a air system schematic. I don't suppose you saw one in any of the paperwork or manuals that came with the coach? Two of the most useful tools you can have when working on these old coaches are the air system and the 12 volt electrical system schematics. Without them, trouble shooting is really difficult. Not impossible...but difficult.

As suggested above by Mike, you will need to figure out how the air is routed around your coach. Basically, there is a air pump somewhere on the coach. It may be electrical (12 volt), or it may be mechanically driven off the engine. Pressure from the pump will go to one or more pressure tanks. It may pass through a "air drier" on the way to the tank...or not. From the tank (or tanks) it will be piped to anything that uses air pressure to operate.

Without knowing anything about your system, I would guess air goes from the pump, to a tank, and then up to the control panel on your dash. When you operate the two valves on the control panel you will pump up or deflate the air bags. The two needles on the gauge will show the air pressure in the bags.

Obviously, you will have to replace the damaged bag. You might be able to find a part number on the "good" bag. Until you do that, the whole tag axle suspension will be useless. After you get the bag replaced, then you can proceed with figuring out how the system works.

In the meantime, you might call FOT and see if they can provide you with a air system and electrical schematic.

Re: How Do I Operate Tag Axle Suspension?

Reply #8 – May 16, 2017, 08:54:35 pm

I foreget if you have air brakes or not. If so the compressor will be the front belt and hung under the crankshaft of the engine. IMHO. This will fill an air tank or two/ These wil have cables leading to the edge of the coach and able to to be tugged daily to remove air/water.

If you have juice brakes the air compressor will be 12 volts and mounted closer to the air tank or direct drive the air bags. This system does not require a tank and may not have one . The dash controls look like air valves and not electrical switches. Tip the dash up and have a peek.

Re: How Do I Operate Tag Axle Suspension?

Reply #9 – May 16, 2017, 08:55:06 pm

Unlikely that you will find the part number sticker on the bag. When you look at the rubber bellow you will see the manufacturers name and then in a small oval you will see a number stamped. That is the bellows number. Then you need to look at the top and bottom plate for diameter and layout of bolts/fittings. When you look up the bag in the book you use the bellows number and there will be several with that bellows and different top and bottom plates. You match up what you have based on that. I recommend that you take the whole bag with you if you haven't done it before and let the parts person do it. Also use a truck shop that deals in airbags a lot. Some parts guys won't even ask what it's out of. You can tell them the truth or tell them it's off a lift axle on some home made farm trailer.

I don't know how your system is set up. I would look for your compressor and see if there are any tanks. You could pull the panel with the adjusters and see if the air lines from the delivery side to the airbags will hold air. As well you can see if there is any air supply to it. There are 12 volt air compressors you could install and run line to the supply side.

Re: How Do I Operate Tag Axle Suspension?

Reply #10 – May 16, 2017, 09:50:50 pm

Your 6th photo certainly looks like a air pressure tank. The little valve on the bottom is probably a water (condensate) drain.

I'm guessing the air hose you found in the storage bay does lead to the air tank. If it has a female quick connect fitting, it was probably used as a "tire filler" hose. Most of the later coaches have a hose like this. If it does go to the air tank, you can also use it to put air into the tank. You just need a double male quick connect adapter, and a portable compressor. If you can get a little air pressure built up in the tank, then you can play around with the tag axle control panel, and see what is working and what's not.

Re: How Do I Operate Tag Axle Suspension?

Reply #11 – May 16, 2017, 10:33:33 pm

I wouldn't buy another air bag until you try to put some air in it. It might be that way from driving the coach without any air in it. It might just pump up fine. There must be a compressor somewhere on the coach - and it's apparently not working. It might be a 12 volt unit (first guess) or engine mounted.

Re: How Do I Operate Tag Axle Suspension?

Reply #12 – May 16, 2017, 10:45:25 pm

Those are Williams Air Control valves. They are push/pull. They were used for many years on the

Bostrom air ride seats in large trucks. Go to the back of the valves and open the 'in' fittings to see

if you have air pressure to your valves, if you do retighten those supply lines. Next loosen the lines

that go out to the air bags. Press each valve down and see if the air flows through. If both have air

flowing through, tighten the fittings. Then follow the air through to the bags. If the lines look good,

then go to the bags. Loosen the air lines to them and have some one push in on the air valve and if

you have air to the bags you should be good to go. It takes a good amount of air to fill the bags and

will not happen by just hitting the valve, it will take a little while to fill them both, be patient and watch

the gauge.

Good luck on your project .

Carter-

Re: How Do I Operate Tag Axle Suspension?

Reply #13 – May 17, 2017, 01:51:54 am

From the pictures, one air bag is totally ruptured. has to locate the air compressor if it is still there and powered and operating, first and foremost.

Re: How Do I Operate Tag Axle Suspension?

Reply #14 – May 17, 2017, 07:29:05 am

I can't tell by the pic if that bag is ruptured. It might just be folded up in itself. It's happened to my big truck when working on it at times. Add air and it pops back in place.

Re: How Do I Operate Tag Axle Suspension?

Reply #15 – May 17, 2017, 08:50:25 pm

There is a12 volt compresser I think that it's mounted under the coach either near the tag axle or might be in the area of the step well

Re: How Do I Operate Tag Axle Suspension?

Reply #16 – May 19, 2017, 04:31:30 pm

Okay, So I crawled under to have a look around and lifted the dash.

Picture 1 is something mounted next to the pressure tank. I assume that's the compressor.

Picture 2 is another view of what I think is the compressor. You can see the pressure tank in the top half of the picture.

Picture 3 is the back side of the pressure tank.

Picture 4 is another unknown gizmo that looks like it might be connected to the pressure system somehow.

The dash definitely has air hoses hooked up to the to the valves. I'm not getting pressure to them. But I can't figure out how to turn the compressor on. There are no switches for it anywhere in the coach that I can find. It doesn't seem to turn on when I turn the engine on.

Any ideas how I can turn the compressor on?

Re: How Do I Operate Tag Axle Suspension?

Reply #17 – May 19, 2017, 05:36:43 pm

Does the thing that you think is a compressor have any electric wires attached to it? Anything that looks like a power supply wire?

If you can find a place on it that looks like the power connection, you could try powering it with a long jumper wire off the battery.

That doesn't look like any air compressor I've ever seen, but that doesn't mean anything.

The other doohickie is some kind of valve or regulator. Need a better photo of the top of it (where hoses connect) to make a guess.

Re: How Do I Operate Tag Axle Suspension?

Reply #18 – May 19, 2017, 05:50:07 pm

I started a little Google search. I think I may on the trail of something at least similar to what you have. The thing next to the air tank may actually be a booster for the tag axel brakes. Does your tag axle have brakes? Try looking through the thread linked below, and check out the photos. See if any of it looks close to what you have.

Hydraulic Tag Axle Brake Information - iRV2 Forums

Re: How Do I Operate Tag Axle Suspension?

Reply #19 – May 19, 2017, 06:20:44 pm

In your first post, you had photos of excerpts from a instruction sheet of some kind. Do you have any kind of manual for the tag axle? I think I found parts of a manual with the same info pages as shown in your initial post. Page 22 shows a diagram of a belt driven air compressor. You may have one of these compressors "hidden" in your coach somewhere. Look in all the storage bays and under the coach.

http://truckroadservice.com/barth_attachments/7421043732_Neway_Suspension_Maintenance_Files.pdf

Re: How Do I Operate Tag Axle Suspension?

Reply #20 – May 20, 2017, 01:36:01 am

Pic 1& 2 looks like a vacuum booster for the brake system.

Pic 3 I am clueless on, kind of looks like the reserve air tank?

Pic 4 Looks like an inline fuel pressure regulator.

Carter-

Re: How Do I Operate Tag Axle Suspension?

Reply #21 – May 20, 2017, 08:47:34 am

Quote from: Texas Guy – May 20, 2017, 01:36:01 am

Pic 4 Looks like an inline fuel pressure regulator.

I think it might actually be a Syncronyzer relay valve (transducer). See the photo on the page I linked in reply #18.

Re: How Do I Operate Tag Axle Suspension?

Reply #22 – May 20, 2017, 09:44:30 am

Quote from: Texas Guy – May 20, 2017, 01:36:01 am

Pic 1& 2 looks like a vacuum booster for the brake system.

Pic 3 I am clueless on, kind of looks like the reserve air tank?

Pic 4 Looks like an inline fuel pressure regulator.

Carter-

Carter,
I think you are getting close to what is there. I believe this is what used to be called a Hydrovac brake system and all the parts are part of the brake system. in picture 4 you can see hydraulic brake lines at the frame.
Disclaimer, I could be wrong

Re: How Do I Operate Tag Axle Suspension?

Reply #23 – May 20, 2017, 09:49:37 am

X 2 the declaimer.

Carter-

Re: How Do I Operate Tag Axle Suspension?

Reply #24 – May 20, 2017, 10:21:43 am

Quote from: AKATheAlchemist – May 19, 2017, 04:31:30 pm

The dash definitely has air hoses hooked up to the to the valves. I'm not getting pressure to them. But I can't figure out how to turn the compressor on. There are no switches for it anywhere in the coach that I can find. It doesn't seem to turn on when I turn the engine on.

Any ideas how I can turn the compressor on?

I would try to identify the hose that is the supply and trace it back to the compressor. It could be anywhere, include just behind the front bumper. I'm going to guess it's an electric powered compressor and not engine mounted. Foretravel seems to like the high end Thomas brand so it might look like this: Thomas 12 volt Compressor

I will give my guess on how it might be controlled: Main power comes to it through the ignition (no sense running the compressor when parked). There is an automatic pressure switch that turns it on when pressure is below a set point (say 75 psi) and turns it off at a higher set point (say 100 psi).

I doubt there is a dash ON/OFF switch but look for a fuse for it. Maybe you already know this, but if you coach is like other Foretravels the dash will lift up and expose the wiring along with fuses. A fuse identification diagram will be attached to bottom side of the dash cover. There will not be a lever or handle to lift up the dash - just start pulling up (gently) on the overhanging edge; it hinges on the long side closest to the windshield.

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