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A/C 3rd Gen Controls / 4th Gen Compressor

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A/C 3rd Gen Controls / 4th Gen Compressor

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Old 06-28-2011, 11:16 PM
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A/C 3rd Gen Controls / 4th Gen Compressor

Hey guys, I am struggling with my LS1 A/C compressor wiring and need a little direction. From my searches I see a lot of guys using the 4th Gen controls with the 4th Gen A/C compressor. For my setup I am wanting to mantain the stock 3rd Gen controls with the LS1 compressor.

Dryer is the stock 3rd Gen and I will be using the Hawks conversion lines for connection of it to the LS1 compressor.
http://www.hawksthirdgenparts.com/ls...passkit-1.aspx
As per Hawks website:
"*Note: You will use the stock 3rd Gen preasure switch on the dryer, but on the high side which is the small metal line you must use a 4th Gen preasure switch which is a 3 wire connector." I will be replacing the high side pressure switch with the 4th Gen 3 wire unit.

Where I run into questions are;

1) Can I connect the 4th Gen 3 wire high side pressure switch into my 3rd Gen controls? Are two of the three wires used to replace the stock 2 wire A/C High Pressure cutout switch, with the third wire to be used to provide 12 V to DK GRN wire to the LS1 PCM, Red R17? (AC Request Signal)

My thought is this input to the LS1 PCM would signal PCM to increase idle due to the compressor running.


2) Can I operate the 4th Gen A/C Compressor without a relay as is done with the stock 3rd Gen A/C compressor connection? In review of the 4th Gen wiring, it utilizes a relay for the A/C compressor control.


Here is the stock 3rd Gen controls wiring with my comments added as to what I am planning. Has anyone connected the A/C compressor in this manner or am I way off course?

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Here is the 4th Gen wiring schematic from Clymers manual.
Name:  4thGen_HVAC.jpg
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Old 06-29-2011, 11:42 AM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

1) The 4th gen switch (actually a 3-wire sensor) doesn't bolt onto the thirdgen line. Needs to be the older style 3-wire sensor (found in older cars such as 1990 grand am) if wanting the PCM to control the a/c. The 4th gen switch uses different threads than the threads on the thirdgen high pressure line. You may be able to put the 4th gen sensor on the line but I wouldn't trust it. If using the 3-wire sensor, an a/c request signal sent to the PCM from the thirdgen controls would be needed and a 2-wire switch wouldn't be needed. However, I recommend just using the thirdgen low pressure cycling switch instead since even in a junkyard the grand am sensor is rare to find and isn't cheap new.

2) Yes. The compressor can be wired to cycle just as it does on the thirdgen setup. Just use the low pressure switch that is mounted on the side of the accumulator. One wire goes to your thirdgen controls(or even could work with 4th gen controls) and the other wire goes to the power wire on the compressor. PCM does not need to control the compressor.

Last edited by Firebat; 06-30-2011 at 12:38 AM.
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Old 06-29-2011, 11:42 PM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

Sounds much simpler than I thought...

Is there any concerns of operating the A/C without the 3rd Gen A/C High Pressure switch?

If I want to add the A/C running status to the LS1 PCM to elevate the engine idle when the A/C is running, is this done by feeding 12V to 1) AC Request, or 2) Clutch Status?
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Old 06-29-2011, 11:47 PM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

I just put a fourth gen compressor on my car with all the third gen stuff. Used hawks lines and no high pressure switch. It works but the fan does not come on and the high side goes through the roof plus does not idle up. I am wanting to send 12 volts to the pcm from the third gen controls to i beleive pin 18 on the red connecter which is the request signal and i think it will run the fans and idle it up. Has anyone done this?
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Old 06-29-2011, 11:51 PM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

Yeah that is another concern.

When the stock 3rd Gen A/C is running, it kicks in the fans.
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Old 11-21-2013, 09:39 PM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

So which wiring method did you end up using?
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Old 11-21-2013, 10:20 PM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

According to me, There is minor physical change between A/C 3rd Gen Controls and 4th Gen Compressor.A/C 3rd Gen Controls give less service in comparison to 4th Gen Compressor. Proper Research On this Control, Then Selected Which one is better.
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Old 11-21-2013, 11:24 PM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

Originally Posted by anrique View Post
According to me, There is minor physical change between A/C 3rd Gen Controls and 4th Gen Compressor.A/C 3rd Gen Controls give less service in comparison to 4th Gen Compressor. Proper Research On this Control, Then Selected Which one is better.
Believe me I've done a lot of research. I Haven't found much info on the pros/cons of either wiring style on here to make a decision. A lot of posts, but not many post on how they liked the route they took in regards to performance, etc.
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Old 11-22-2013, 08:07 AM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

Sorry man, I never did complete the A/C install. Had the compressor mounted and wired but with the T roofs providing sufficient cabin cooling, never felt a need to complete the install. (The joys of our Canadian climate... enjoy the warmth of the sun when you can.)

With now moving primarily towards performance, I have removed the A/C compressor and gone with an A/C delete heater box.

The biggest issue I was running into was the sensors and operations mentioned. A discussion with Hawks may be your best route.
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Old 11-22-2013, 12:16 PM
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Re: A/C 3rd Gen Controls / 4th Gen Compressor

Originally Posted by HP52TA View Post
Sorry man, I never did complete the A/C install. Had the compressor mounted and wired but with the T roofs providing sufficient cabin cooling, never felt a need to complete the install. (The joys of our Canadian climate... enjoy the warmth of the sun when you can.)

With now moving primarily towards performance, I have removed the A/C compressor and gone with an A/C delete heater box.

The biggest issue I was running into was the sensors and operations mentioned. A discussion with Hawks may be your best route.
Thanks for the updates. Obviously it's not going to be a huge necessity but I would like to have a good working AC system even in a convertible. I've been in the same boat before, getting a plan together and posting about it and then go a totally different direction.

Heck Ive even thought a AC delet box would look a lot cleaner under the hood!

Last edited by kycellrepair; 11-22-2013 at 10:35 PM.
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