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Old 05-22-2016, 08:06 AM   #1
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Working on the airbag system.

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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Old 05-22-2016, 11:32 AM   #2
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With the components you have in place your wiring should be something similar to the attached sketch.
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ID:	262977

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


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Old 05-22-2016, 12:51 PM   #3
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Quote:
Originally Posted by Flysoncloud View Post
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.
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Old 05-22-2016, 01:05 PM   #4
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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
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Old 05-22-2016, 01:16 PM   #5
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Originally Posted by mayco View Post
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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Old 05-22-2016, 01:29 PM   #6
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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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Old 05-22-2016, 02:15 PM   #7
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Quote:
Originally Posted by Flysoncloud View Post
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.
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Old 05-22-2016, 02:21 PM   #8
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Quote:
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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.
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.

Quote:
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.

Quote:
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.

Quote:
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.
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Old 05-22-2016, 02:58 PM   #9
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Quote:
Originally Posted by bkahler View Post
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.
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Old 05-22-2016, 04:02 PM   #10
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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.

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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.
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Old 05-22-2016, 05:47 PM   #11
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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.
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Old 05-22-2016, 07:07 PM   #12
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I understand it is Sunday and our brains need time to catch up.
I'll take any excuse I can get!

Quote:
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.

Quote:
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.
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Old 05-22-2016, 09:25 PM   #13
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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?
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Old 05-23-2016, 05:10 AM   #14
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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!
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