Fummins ac compressor issues cont'd - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 3 (permalink) Old 05-31-2019, 02:39 AM Thread Starter
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Fummins ac compressor issues cont'd

Hey everyone,

So I posted on here before about my ac woes. I've been messing with this off and on for about 2 months. I'm kind of at my wits end, I think maybe I'm looking in the wrong place.

Here's the deal.
New compressor, accumulator, condenser, and lines when I installed the cummins.
In the process of trying to figure out why the compressor wont turn on I replaced both the ac clutch cycling switch and dual pressure switch, first with autozone parts, then I thought maybe it was bad sensors so I got oem ford. Still nothing.
I even found though this whole process with evac and recharge 5 or 6 times that my orifice tube was clogged. That fixed my pressures. They're about 70psi static and with the compressor on its 35-40 and about 170 at 70ish degrees.
If I jump the red/yel to the tan/lt.grn at the dual pressure switch the clutch will engage and get cold.
I've confirmed I have 14v on the violet at the clutch switch, and when its plugged in I have 14v at the dual pressure switch. I also checked that the blk/yel was getting a good ground.

So this has me thinking maybe something else I'm overlooking is causing it. I've heard the electronic fan clutch is somehow tied into the ac program so it comes on with the ac command. Could a fan issue cause the compressor to not kick on?

Can anyone explain to me the purpose of the second tan/lt.grn wire on the dual pressure switch? It shows to be switched to ground but the schematic says its "ac press switch input"
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post #2 of 3 (permalink) Old 05-31-2019, 02:45 AM Thread Starter
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03 f450 6.0 truck
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post #3 of 3 (permalink) Old 05-31-2019, 08:13 PM
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Re: Fummins ac compressor issues cont'd

Ok first off should have continued in the thread u already started to make it easier for people in the future to find info.
So looking at the diagram if u are jumping pin 1 to pin 4 like u say then the problem is at the switch either it is not reading the pressure from the system(ie something wrong with the valve the switch screws into) or something is wrong with the switch its self. The violet wire feeds thru the cycling switch to the red/yellow wire(pin1 dual pressure switch) then out of switch on pin4 tan/lt grn then to the computer. so with u jumping says the computer will turn it on if the dual pressure switch is working right. so u need to focus on figuring out why the dual pressure switch is open when it should be closed.

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