Working on the airbag system.

[Flysoncloud]

So today I started digging more and poking around with the old volt meter. In the cabinet, curb side bed room, full bed. I find this box with a switch.

This switch will turn the compressor on when everything is hooked up. Behind the box I found the pump and pressure switch and also a solenoid.

The solenoid was energizing as soon as I hooked up the battery causing my 12v @ almost 1 amp draw. I looked though the book and found the hot wire on the solenoid starts at the fuse panel in the dash. It is just hooked to a constant power supply without a fuse.

Once I pulled this wire from the solenoid my power draw went away. Also the switch no longer worked when the wire was unhooked. My book says that the pressure switch is set for 85 pounds and should shut off at 100 pounds. I have 65 psi in the tank.

The pressure switch remained close the whole time regardless of power.

So now I wonder what is wrong here. Why is the a additional switch for the compressor? Why is the solenoid getting constant power? Could it be because my pressure switch is bad and won't open? Ahhhh the fun of a new project.





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[bkahler]

With the components you have in place your wiring should be something similar to the attached sketch.


If you ask me your pressure switch is probably bad or miss-wired inside.


Brad

[Smartstream]

Originally Posted by Flysoncloud

So today I started digging more and poking around with the old volt meter. In the cabinet, curb side bed room, full bed. I find this box with a switch.

This switch will turn the compressor on when everything is hooked up. Behind the box I found the pump and pressure switch and also a solenoid.

The solenoid was energizing as soon as I hooked up the battery causing my 12v @ almost 1 amp draw. I looked though the book and found the hot wire on the solenoid starts at the fuse panel in the dash. It is just hooked to a constant power supply without a fuse.

Once I pulled this wire from the solenoid my power draw went away. Also the switch no longer worked when the wire was unhooked. My book says that the pressure switch is set for 85 pounds and should shut off at 100 pounds. I have 65 psi in the tank.

The pressure switch remained close the whole time regardless of power.

So now I wonder what is wrong here. Why is the a additional switch for the compressor? Why is the solenoid getting constant power? Could it be because my pressure switch is bad and won't open? Ahhhh the fun of a new project.



Attachment 262967Attachment 262968Attachment 262969


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By the hot wire on the solenoid are you referring to the switched wire or the solenoid energizing relay wire? The switched wire should be hot through a fuse but should draw no current until the relay is energized to close the contacts. The solenoid relay should only be energized when the ignition switch is on.

The contacts on the pressure switch should be closed until the tank pressure reaches or exceeds 100 psi. The pressure switch should be the last switch before the compressor.

It the toggle switch turns on the compressor I would think the problem is in the solenoid or its wiring. If you run the compressor with the toggle switch will the pressure switch open at 100 psi and turn off the compressor? If yes then the pressure switch is fine.

[mayco]

You could clean that all up with one of these...
http://www.amazon.com/Viair-90110-Pr.../dp/B000FQ1HM4

Im real happy with mine so far.

Mke

[Flysoncloud]

Originally Posted by mayco

You could clean that all up with one of these...
http://www.amazon.com/Viair-90110-Pr.../dp/B000FQ1HM4

Im real happy with mine so far.

Mke

I like clean!


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[Flysoncloud]

In the first picture you can see a wire that is unhooked. That wire comes off a constant hot spade from the fuse box. It goes to the little stud on the side of the solenoid that is on the right side in the picture. When that wire is attached the solenoid closes and causes the amp draw. I did not let the pressure in the tank get over 65 pounds until I knew for sure what the max pressure was. I have not traced any other wires back. I am guessing one of them goes to a keyed hot fuse in the box.
I did find the theory of operations and how it should be wired in my book. Mine looks nothing like it at all. I will have the coach at the house on Tuesday and dig a little deeper. I did get a new solenoid so I will put that in too. Kicking around the idea of the part posted earlier and just cleaning the whole thing up.
I wonder if the PO put the switch in so he could air up the tank to fill other things like mattresses or such. Without needing to turn on the key.


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[Smartstream]

Originally Posted by Flysoncloud

In the first picture you can see a wire that is unhooked. That wire comes off a constant hot spade from the fuse box. It goes to the little stud on the side of the solenoid that is on the right side in the picture. When that wire is attached the solenoid closes and causes the amp draw. I did not let the pressure in the tank get over 65 pounds until I knew for sure what the max pressure was. I have not traced any other wires back. I am guessing one of them goes to a keyed hot fuse in the box.
I did find the theory of operations and how it should be wired in my book. Mine looks nothing like it at all. I will have the coach at the house on Tuesday and dig a little deeper. I did get a new solenoid so I will put that in too. Kicking around the idea of the part posted earlier and just cleaning the whole thing up.
I wonder if the PO put the switch in so he could air up the tank to fill other things like mattresses or such. Without needing to turn on the key.


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The small stud on the front of the solenoid is the coil that operates the solenoid, you should hear a click when that wire is connected. That wire should only be hot when the ignition switch is on. The large terminals on the side of the solenoid carry the heavy load, one side is always hot and the other side is only hot when the coil is energized. This is the wire that goes to the pressure switch and ultimately the compressor.

Myself and many others on this site run the heavy load wire from the battery through a fuse to the solenoid. Airstream originally ran this wire from the dash fuse block to the pressure switch but it is such a heavy load that it caused many problems. An ignition switch controlled wire has no problem with the 1 amp draw of the solenoid coil.

If you move the dash end of the yellow wire you disconnected to an ignition switch controlled fuse and insure that solenoid is functioning properly you should be OK.

[bkahler]

Originally Posted by Smartstream

The small stud on the front of the solenoid is the coil that operates the solenoid, you should hear a click when that wire is connected. That wire should only be hot when the ignition switch is on.

It should only be hot when the ignition is on AND the pressure switch is closed. The pressure switch should be in series with the wire coming from the fuse block and the contact in the pressure switch should energize the solenoid. If the pressure switch is installed in series with the contact of the solenoid going to the compressor the high current draw will eventually damage the pressure switch contacts.

The large terminals on the side of the solenoid carry the heavy load, one side is always hot and the other side is only hot when the coil is energized. This is the wire that goes to the pressure switch and ultimately the compressor.

The pressure switch should not be in this circuit. See comment above.

Myself and many others on this site run the heavy load wire from the battery through a fuse to the solenoid. Airstream originally ran this wire from the dash fuse block to the pressure switch but it is such a heavy load that it caused many problems. An ignition switch controlled wire has no problem with the 1 amp draw of the solenoid coil.

This is definitely a highly recommended modification. The sketch I attached previously shows this configuration.

If you move the dash end of the yellow wire you disconnected to an ignition switch controlled fuse and insure that solenoid is functioning properly you should be OK.

[Smartstream]

Originally Posted by bkahler

It should only be hot when the ignition is on AND the pressure switch is closed. The pressure switch should be in series with the wire coming from the fuse block and the contact in the pressure switch should energize the solenoid. If the pressure switch is installed in series with the contact of the solenoid going to the compressor the high current draw will eventually damage the pressure switch contacts.



The pressure switch should not be in this circuit. See comment above.



This is definitely a highly recommended modification. The sketch I attached previously shows this configuration.

I agree that the pressure switch can be ahead of the solenoid coil and that is a good suggestion. That being said I don't recall seeing many problems with the pressure switch as they do have pretty heavy contacts. The problem has always been the entire load going through the ignition switch and fuse block on the dash.

Brad I do have to take issue with your sketch. If you energize the toggle switch you bypass the pressure switch and the compressor will run until something fails from over pressure or you flip the toggle switch. Bottom line is the components must be rated to carry the intended load, both current and pressure and the safeties located so that they cannot be bypassed.

[bkahler]

Originally Posted by Smartstream

I agree that the pressure switch can be ahead of the solenoid coil and that is a good suggestion. That being said I don't recall seeing many problems with the pressure switch as they do have pretty heavy contacts. The problem has always been the entire load going through the ignition switch and fuse block on the dash.

Brad I do have to take issue with your sketch. If you energize the toggle switch you bypass the pressure switch and the compressor will run until something fails from over pressure or you flip the toggle switch. Bottom line is the components must be rated to carry the intended load, both current and pressure and the safeties located so that they cannot be bypassed.

Good catch Dan

I originally drew the sketch to show how the pressure switch controls the solenoid and then added the switch as an after thought without thinking it through. The revised sketch shows how the switch should be. Also the sketch does not show inline fuses, etc. I mainly wanted to show the flow of current for the solenoid, pressure switch and pump.



The problem I've seen with using pressure switches to start and stop high current loads, especially in DC circuits is the lower the voltage the higher the current and with the long wire run coming from the fuse block the way Airstream originally did it meant there was a LOT of current passing through the pressure switch due to the voltage drop along that long yellow wire. Since the pressure switch is what was starting and stopping the pump that would create a pretty good arc on the contacts each time it started and stopped.

My back ground is instrumentation and controls so to me switch contacts like those in pressure switches are used for controlling devices such as solenoids, not heavy current loads like pumps.

[Smartstream]

Originally Posted by bkahler

Good catch Dan

I originally drew the sketch to show how the pressure switch controls the solenoid and then added the switch as an after thought without thinking it through. The revised sketch shows how the switch should be. Also the sketch does not show inline fuses, etc. I mainly wanted to show the flow of current for the solenoid, pressure switch and pump.

Attachment 262997

The problem I've seen with using pressure switches to start and stop high current loads, especially in DC circuits is the lower the voltage the higher the current and with the long wire run coming from the fuse block the way Airstream originally did it meant there was a LOT of current passing through the pressure switch due to the voltage drop along that long yellow wire. Since the pressure switch is what was starting and stopping the pump that would create a pretty good arc on the contacts each time it started and stopped.

My back ground is instrumentation and controls so to me switch contacts like those in pressure switches are used for controlling devices such as solenoids, not heavy current loads like pumps.

I understand it is Sunday and our brains need time to catch up. I wonder if the Viair set up Mayco linked to is set up with the pressure switch before or after the solenoid.

Back to Flysoncloud's original question I think somebody attempted to improve the system with the addition of the solenoid in the first picture. The first problem is energizing the solenoid coil continuously. I wonder if the solenoid has failed. Also curious where they sourced the load current (black wire) for the solenoid. It looks like the original Square D pressure switch in the back without the cover but I don't recognize the round device in the middle. It should be a relatively simple fix once he chases down the wiring.

[bkahler]

Originally Posted by Smartstream

I understand it is Sunday and our brains need time to catch up.

I'll take any excuse I can get!

I wonder if the Viair set up Mayco linked to is set up with the pressure switch before or after the solenoid.

My guess is the pressure switch is in line with pump motor. That's a cheaper design to implement.

Back to Flysoncloud's original question I think somebody attempted to improve the system with the addition of the solenoid in the first picture. The first problem is energizing the solenoid coil continuously. I wonder if the solenoid has failed. Also curious where they sourced the load current (black wire) for the solenoid. It looks like the original Square D pressure switch in the back without the cover but I don't recognize the round device in the middle. It should be a relatively simple fix once he chases down the wiring.

I think all of the components are as delivered from Airstream. The 86 345 that I dismantled had a very similar arrangement for the pump control. Looking at the mounting bracket it sure looks like something Airstream would do.

Assuming this 345 has an air pressure gauge in the dash I would say that round device is a pressure transducer. That 345 I had also had a pressure gauge in the dash and a transducer like the one in the picture.

As far as what the problem is that's hard to say without seeing a wiring diagram of how it's actually wired right now. Trying to sort out the wires from the pictures isn't easy but it looks like at least one of the yellow wires from the pressure switch is disconnected. I think it's been jury rigged to get the compressor to run.

If Flysoncloud could create a sketch of the current wiring I'm sure we can point out what needs to go where to make it work properly.

[Smartstream]

Originally Posted by bkahler

I'll take any excuse I can get!



My guess is the pressure switch is in line with pump motor. That's a cheaper design to implement.



I think all of the components are as delivered from Airstream. The 86 345 that I dismantled had a very similar arrangement for the pump control. Looking at the mounting bracket it sure looks like something Airstream would do.

Assuming this 345 has an air pressure gauge in the dash I would say that round device is a pressure transducer. That 345 I had also had a pressure gauge in the dash and a transducer like the one in the picture.

As far as what the problem is that's hard to say without seeing a wiring diagram of how it's actually wired right now. Trying to sort out the wires from the pictures isn't easy but it looks like at least one of the yellow wires from the pressure switch is disconnected. I think it's been jury rigged to get the compressor to run.

If Flysoncloud could create a sketch of the current wiring I'm sure we can point out what needs to go where to make it work properly.

Interesting, what year was your 34.5? On the early 280's and 310's I have seen the compressor is powered by a 20 amp fuse on the dash with no relay or solenoid. Also my dash gauge is mechanical with a 1/16th plastic tube running from the bags up the right frame rail to the dash. Mine shows bag pressure rather then tank pressure. You can watch the needle bounce as you go over bumps. Also pressure goes up several psi s the holding tanks fill up. I wonder if the changes came on the newer rigs or bigger rigs?

[bkahler]

Originally Posted by Smartstream

Interesting, what year was your 34.5? On the early 280's and 310's I have seen the compressor is powered by a 20 amp fuse on the dash with no relay or solenoid. Also my dash gauge is mechanical with a 1/16th plastic tube running from the bags up the right frame rail to the dash. Mine shows bag pressure rather then tank pressure. You can watch the needle bounce as you go over bumps. Also pressure goes up several psi s the holding tanks fill up. I wonder if the changes came on the newer rigs or bigger rigs?

The 345 was a 1986 model. My old 84 310 didn't have a pressure gauge and was wired like you described with a yellow wire running from the fuse block back to the pressure switch.

It wouldn't surprise me if changes were phased in over various models over various years. Nothing else Airstream did made any sense so why should this!

[Flysoncloud]

I went to get the Moho today and the truck battery was dead again. I get a good draw from something on the battery fuse in the dash. I can pull the fuse and the draw goes away. I am going to guess that it is something to do with the whole airbag set up. More on that later.

This is my best drawing so far. When I got home from the lot I plugged in the yellow wire that seemed to kill the system and nothing happened. I went in and started taking voltage measurements and boom it started running. Ran to about 85 pounds and shut off. With the switch on everything ran fine. With the switch off nothing ran. At 85psi the compressor shut off and the contacts were open. Once the contacts opened my amp draw went way down but I still have a voltage/amp thief. When I pull the radio fuse all of my draw goes away on the amps side but I still have a 12 v draw with not enough amps to measure and no light using a test light. Something still isn't correct as this all will run without the key on.


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[Flysoncloud]

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[Flysoncloud]

Radio fuse in

Radio fuse out





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[bkahler]

Your diagram pretty much matches what I would expect to see for a compressor installation.

I redrew your sketch to show things a little more clearly.


I can think of three possibilities as to why it seems to be erratic. The pressure switch contacts could be going bad which I don't think is the case since the pressure switch is not wired on the high current side feeding the compressor motor. It's also possible the pressure switch is just failing inside and not registering pressure properly.

Second, The circuit breaker (You list it as a relay) could be going bad and third, the solenoid is going bad. Or one other possibility is a loose wire somewhere.

Based on your symptoms and your wiring my diagram I would consider the solenoid to be the most likely culprit.

The reason you were getting a 1 amp draw previously is the pressure switch was closed calling for the compressor to start which energized the solenoid. However with the toggle switch in the off position the compressor can't run. Whoever installed the toggle switch apparently wanted to make sure the compressor wouldn't run unless they wanted it to but they failed to take into account the solenoid would still be energized if the pressure switch was closed.

An easy fix would be to move the toggle switch to the left side of the pressure switch which is where it should be anyway and run the ignition hot signal from the fuse block directly to the pressure switch.




Also, the white wire that comes from the pressure transducer should head to the dash for an air pressure gauge. The white wire likely will not have a voltage reading or if it does it will be a low reading.


Brad

[Flysoncloud]

I have a low pressure buzzer in the dash somewhere so I will guess that the white wire goes to it since I do not have a gauge in the dash. There is a gauge in the rear curb side hatch. If I understand you correctly I can pull the switch and attach those wires then put the switch in the yellow wire that is always hot? Then move that wire to a spade on the fuse block that is only hot when the key is on?


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[Smartstream]

I agree with Brad with one exception, the control feed from the dash fuse block needs to be controlled by the ignition switch. Other then testing there is no need to run the compressor to inflate the air bags unless the engine is running and you are moving the coach.

I can't guess at the amp rating of the toggle switch but most over the counter switches like that won't carry the amperage of the compressor. Your sketch shows it to be in series with the compressor and I would start checking there.

Referring to Brad's sketch the upper circuit would be the control circuit and should never see more than 1 or 2 amps. The lower circuit would be the load and will carry the approximately 20 amps of the compressor. Because you are drawing 1 amp with the solenoid coil wire connected the pressure switch contacts must be good. With that wire connected use your test light to check the load terminals on both sides of the solenoid, relay/circuit breaker and the toggle switch, they all must be hot for the compressor to run. If they are all hot and still no joy look for loose connections and the compressor ground.

With the cover off the pressure switch you can see the contacts and watch the paddles open and close as the switch operates. You can even operate it manually if you want. By the way if you do get a dirty contact just switch to another pair, you have several spares.

I'm not sure if your radio fuse has any thing to do with the problem unless there are strange things happening in the fuse box. Looking at the dash wiring in these rigs anything is possible.