Truck PCM A/C wiring
05-20-2010, 05:53 PM
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Truck PCM A/C wiring I have an F-body accessory set and compressor on an LM7 using a 2001 Silverado PCM.
I remember reading a previous post discussing the trucks using a different pressure switch setup than the f-body. I have spent the last few hours searching for this thread again but for the life of me can not find it.
I will be having lines made this weekend and need to confirm if I can use the single pressure switch setup like on the f-body or if something else must be done.
I remember reading a previous post discussing the trucks using a different pressure switch setup than the f-body. I have spent the last few hours searching for this thread again but for the life of me can not find it.
I will be having lines made this weekend and need to confirm if I can use the single pressure switch setup like on the f-body or if something else must be done.
05-20-2010, 06:41 PM
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I actually just found that post using a couple more creative search terms.
I really dont understand how the truck PCM uses no pressure sensor at all.
I have a truck A/C line section sitting right here and it surely has a pressure sensor in it. I also have a stock harness which also has a pressure sensor plug and wiring.
I really dont understand how the truck PCM uses no pressure sensor at all.
I have a truck A/C line section sitting right here and it surely has a pressure sensor in it. I also have a stock harness which also has a pressure sensor plug and wiring.
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05-20-2010, 11:55 PM
#8
The F-Body pressure sensor reports the exact pressure back to the PCM. On the trucks they use an older style setup which has a pressure switch. On those the PCM has no idea what the actual pressure is, just that the low side of the system has over 25? psi IIRC can`t remember the exact pressure.
05-24-2010, 11:18 AM
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G-body
So what what sensor(s) should I tell my A/C guy to install in the lines? The truck system shows two pressure sensors but from what it looks like in the thirdgen thread only one of them is necessary, but which one?
He gave me a general G/M pressure switch part#, but he is accustomed to setting up systems without PCM control of any kind. I am usually more than willing to do some digging on these type of things but I am working on a very limited time frame.
So what what sensor(s) should I tell my A/C guy to install in the lines? The truck system shows two pressure sensors but from what it looks like in the thirdgen thread only one of them is necessary, but which one?
He gave me a general G/M pressure switch part#, but he is accustomed to setting up systems without PCM control of any kind. I am usually more than willing to do some digging on these type of things but I am working on a very limited time frame.
05-24-2010, 01:03 PM
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I just spoke with a tech at scoggin dickey.
He said there was no need for either of the high side sensors. He said grounds those pins should be enough for the PCM to operate of just the low side(accumulator) switch. He was also confident that both the truck and f-body systems use the same sensor in this position, but the 3 pin version drives an external HVAC module in some systems.
Does any of that sound right?
He said there was no need for either of the high side sensors. He said grounds those pins should be enough for the PCM to operate of just the low side(accumulator) switch. He was also confident that both the truck and f-body systems use the same sensor in this position, but the 3 pin version drives an external HVAC module in some systems.
Does any of that sound right?
05-24-2010, 11:40 PM
#16
On a 2001 there are 3 pressure sensors.
1. A/C high pressure recirculation switch. Only used for the recirculation you don`t need this.
2. A/C high pressure switch. Just keeps the A/C pressure below the max safe level if theres a problem. Not needed, if the system goes over pressure on the high side theres a mechanical overpressure valve that will blow off freon.
3. A/C low pressure switch. You will need this one. it cycles the compressor to keep the low pressure side from freezing solid and icing.
1. A/C high pressure recirculation switch. Only used for the recirculation you don`t need this.
2. A/C high pressure switch. Just keeps the A/C pressure below the max safe level if theres a problem. Not needed, if the system goes over pressure on the high side theres a mechanical overpressure valve that will blow off freon.
3. A/C low pressure switch. You will need this one. it cycles the compressor to keep the low pressure side from freezing solid and icing.
05-29-2010, 05:32 PM
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I wired everything as show in the thirdgen.org diagram.
The PCM is not grounding pin 43 with 12+ at pin 17.
I think this may have to do with the need to ground (or give 12+) to the high side pressure switch PCM input.
Looking at PCM diagram it looks like this may be pin 55 on the C2 connector. It is labeled as CYC SW IN and shows (----->to A/C system).
Can anyone confirm if this is the right pin and if it needs ground or 12+?
The PCM is not grounding pin 43 with 12+ at pin 17.
I think this may have to do with the need to ground (or give 12+) to the high side pressure switch PCM input.
Looking at PCM diagram it looks like this may be pin 55 on the C2 connector. It is labeled as CYC SW IN and shows (----->to A/C system).
Can anyone confirm if this is the right pin and if it needs ground or 12+?
