On-Board-Air 12V wiring question

alex00 · Feb 5, 2014

I wanted to bounce an idea off the group, trying to make sure my logic is sound.

I have the Viair Constant Duty On Board Air system. Compressor, tank, pressure switch, gauge and system on/off switch.

The typical wiring per the instructions is to run ignition switched power to the system on/off switch. Run power from the system on/off switch to the pressure switch, and 12V fused power from the battery to the pressure switch. From the pressure switch to the compressor, as well as a ground to the chassis. This is all well and good, and I can easily run this configuration.

However, my Ram has the upfitter switches on the dash. Each switch is ignition controlled, and provides fused, relayed power out of a plug in the engine compartment. What I want to do is jumper both the positive leads on the Viair pressure switch, and provide all the power from the one positive lead from the upfitter switch. My thinking is that as long as I have ignition switched and full relay power going to both leads of the pressure switch, it won't care that it came from one lead.

This is the pressure switch:

This is the Viair Wiring Diagram:

This is what I want to do:

If you can think of a better way please let me know. Thank you!

ETA: I called Viair, and they weren't completely sure. They thought it would work, but had never run across this scenario.

cookie · Feb 5, 2014

The only problem I see with your proposed wiring is that the wire from your outfitter switch may not be big enough. Also the contacts on the switch may not handle what is thrown at them when the compressor is turned on.
The large wire to the relay is what powers the Viair. The small wire is what activates the relay.
I would go with the wiring recommended by Viair.

Peace
Dave

jdamude · Feb 5, 2014

alex00 said:
I wanted to bounce an idea off the group, trying to make sure my logic is sound.

I have the Viair Constant Duty On Board Air system. Compressor, tank, pressure switch, gauge and system on/off switch.

The typical wiring per the instructions is to run ignition switched power to the system on/off switch. Run power from the system on/off switch to the pressure switch, and 12V fused power from the battery to the pressure switch. From the pressure switch to the compressor, as well as a ground to the chassis. This is all well and good, and I can easily run this configuration.

However, my Ram has the upfitter switches on the dash. Each switch is ignition controlled, and provides fused, relayed power out of a plug in the engine compartment. What I want to do is jumper both the positive leads on the Viair pressure switch, and provide all the power from the one positive lead from the upfitter switch. My thinking is that as long as I have ignition switched and full relay power going to both leads of the pressure switch, it won't care that it came from one lead.

This is the pressure switch:
View attachment 28353

This is the Viair Wiring Diagram:
View attachment 28354

This is what I want to do:
View attachment 28355

If you can think of a better way please let me know. Thank you!

ETA: I called Viair, and they weren't completely sure. They thought it would work, but had never run across this scenario.

I did the same with my system on a Ford F250. On the Ford up fitter switches there are two 25 amp switches and two 10 amp switches. We used one of the 25 amp switches. You will need to identify which one of your switches will carry the amperage required.

alex00 · Feb 5, 2014

jdamude said:
I did the same with my system on a Ford F250. On the Ford up fitter switches there are two 25 amp switches and two 10 amp switches. We used one of the 25 amp switches. You will need to identify which one of your switches will carry the amperage required.

Jeff, per the Ram upfitter diagram, I have two 40 amp, two 25 amp and one 20 amp fused wires. All power lead out wires are 12 awg. The Viair provides a 30 amp fuse. Would you hook to the 25 amp switch without Viair's 30 amp fuse, or hook to the 40 amp switch and put the 30 amp in-line?

cookie said:
The only problem I see with your proposed wiring is that the wire from your outfitter switch may not be big enough. Also the contacts on the switch may not handle what is thrown at them when the compressor is turned on.
The large wire to the relay is what powers the Viair. The small wire is what activates the relay.
I would go with the wiring recommended by Viair.

Peace
Dave

Dave, the wire provided by Viair with the inline fuse is 12 awg, fused for 30 amps. The Ram's output wire is 12 awg, and fused for either 25 or 40 amps, depending on which position. I know what you mean about the contacts of the switches, but this isn't the normal switch setup. The dash switch powers a relay, which sends power to the accessory of your choice. Assuming the Ram give full 40/25 switch protected amps, I take it that jumping the switch and power lead is OK to do?

Thank you both, I really appreciate the quick replies.

emm4273610re · Feb 6, 2014

First I must say very nice truck. Almost ready to make a move for one myself. My question is what model air system are you using? Are you planning for aftermarket bags for the suspension? I am unsure to wait for the factory air suspension or install aftermarket bags like I have now. Where are you mounting the tank and such? More details on your install would be great if you could. Thanks

alex00 · Feb 6, 2014

emm4273610re said:
First I must say very nice truck. Almost ready to make a move for one myself. My question is what model air system are you using? Are you planning for aftermarket bags for the suspension? I am unsure to wait for the factory air suspension or install aftermarket bags like I have now. Where are you mounting the tank and such? More details on your install would be great if you could. Thanks

Thank you. I am using the Viair constant duty (model 10007). It uses the 450C compressor with a 100% duty cycle. I have the Firestone bags (part 2560) that shipped this morning. I plan to mount the tank on the underside of the bed, passenger side, forward of the axle. There are two unused threaded holes that accept M12 1.25 threaded bolts. I will make a 10"x22" plate to hold the tank and compressor. I was planning to do the work this weekend, but the rain is here, and my truck won't fit in the garage because of some boxes. I will post up pictures as soon as I finish the install. Feel free to PM me, if I forget to post them in a week or so.

I was going to wait for the factory air suspension. I learned from DesertThumper that they wouldn't be produced until mid-April at the soonest. That would put a delivery date on a new order at July. There is no way I was going to wait any longer for just air bags. I was under the impression the ride would be smoother because they lose some leaf springs and make up the difference with the bags. Truth be told the ride right now is very smooth. Coming from an '05 Ram Dually, this thing floats like a Cadillac. I can't tell you whether to wait or not, but to me, the bags were not worth waiting for.

On-Board-Air 12V wiring question

alex00

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cookie

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jdamude

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alex00

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emm4273610re

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alex00

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