Can you give us a little more to go on?
What PCM
What calibration
What AC compressor
What wiring did you use?

Things like that

 

Can you give us a little more to go on?
What PCM
What calibration
What AC compressor
What wiring did you use?

Things like that

I am considering the LS swap in my 95 Impala. I see you did the LS7 in your wagon. Just curious but what kind of gas mileage do you get with 525 horsepower in the wagon?
Also, the LS I’m considering is the L9H 6.2. What accessory brackets do you think I may need? A/C, power steering and alternator? I certainly appreciate any insight you can give me since you are familiar with doing a swap. Thanks, Jerry.

 

Using a Holley terminator x max. I just ran their harness as standalone for the engine and left everything else as far as the car's harness there. The entire a/c system is factory. I charged it with the machine and used a jumper to run the compressor and it works fine. Just need to know how to get the digital control in the car to kick on the compressor. I'm thinking there has to be a way to fool it into thinking it's connected to a running engine.

 

Well, I see the only thing your ECU can do is shut of AC over a certain throttle angle, nothing else.

The stock Buick system , when the control head requests the clutch, 12 volts comes out of D14 on the control to the low pressure switch on the Drier ( green wire)
If pressure is high enough, the 12 volt signal goes down the blue 214 wire to PCM plug C2 terminal 1

IF the PCM conditions are met
RPM
TPS
Temp
AC pressure
Steering pressure
few other things

then the PCM grounds C4 terminal 8 which pulls in the compressor relay and away we go.

So, in the simplest terms , if you took a relay and put 85 on the blue wire coming out of the drier low pressure switch , ground 86 , ground 30 , connect 87 to the old PCM wire that was on C4 terminal 8 it would work.

Problem is,
The fans would not come on automatically. You need air across the condenser even if the water temp is normal.
Also the system pressure is not monitored and the compressor would keep running if the pressure went sky high.

There are trinary pressure switches you can add to the system for protection and fan operation based on pressures.

You can also wire the throttle based Terminator control wire into the relay circuit so , at least the clutch can shut off at large throttle openings.

I will try and dig up some of my notes.
My swap was 8 years ago and I am a little fuzzy

 

Notes would be helpful. Sometimes without being able to look at a diagram my head spins. It seems to me like I ought to be able to somehow tell the control unit all those things are okay and just send everything on through.

 

Do you have a factory service manual ?
You really need one .

What compessor did you use?

It seems to me like I ought to be able to somehow tell the control unit all those things are okay and just send everything on through.

You are missing the point .
The AC control makes a simple 12 volt "on" "request" to the original LT1 PCM .
It was the now gone PCM that looked at , assessed perimeters.
If it decided it was time to turn on the clutch, it grounds a wire so the AC clutch relay comes on.

You don't have anything in the car anymore that watch system pressures.
From what I read on your Holley , it can only turn on or off the AC based on throttle position.

This is why you will have to add a Trinary switch

https://www.compressorworks.com/Upload/Four%20Seasons/documents/Tech%20Tips/English/4S%20365%20TRINARY%20SWITCHES.PDF

This video is not exactly how I would wire one but it gives you some basic info

You can likely find a switch that will replace the original pressure transducer near the rad support because you have nothing in the car anymore to use that info.
I personally welded a new boss so I could keep the transducer because I will in future have need for that data.

Hard to know someones knowledge and abilities over the internet.
Basically, you need to convert the 12v "on" coming through the firewall to a ground to the AC clutch relay.
In that circuit, you need to add the trinary switch to protect the system from high pressure.;
The other two wires on the trinary will be wired to ground the fan relay so the fans come on with pressure rise to 250 psi

 

Gotcha, so basically take the signal from the control unit and then wire a standalone a/c harness thereby bypassing the pcm? I think you're right about needing the manual. I've been getting by with a friend at a shop who has alldata.

 

You can probably just get away with a less efficient set up if you don't mind some running fan drag at speed. I've been running my 85 mustang that way for years. The factory efi computer only controls the cut out relay as in under load similar to yours. The AC demand goes thru that relay to the pressure cycling switch then on to the compressor. When i used a 134 conversion system with new compressor and etc, the it added a high side switch to add in series. My fans come on, I have ability to run two different ways, either in parallel with the compressor, or i can have them come one as soon as AC demand is selected. Though fan isn't need at speeds, it still works fine. Eventually i'll wire in the PCM's fan control which will know when to turn off the fans. Right now they are just coolant temp activated. The stock PCM didn't have the fan IC installed like later model mustangs. I soldered in the missing components and now just need to one day finish the wiring to the fans..

 

Mileage, hard to say
The only time I paid attention was one trip with some terror rides mixed in
High teens.
It might be better now as I am always tinkering.
In town, lead foot, lumpy cam, I don't even want to know
Fuel gauge appears to be directly connected to the throttle pedal.

Accessories, unfortunately mine is a bit of a one off with corvette parts but custom AC mounting with it ahead of the main drive pulleys.

If you can weld and machine, I would be happy to share what I did.
Far from a " obtain parts, bolt on " deal.

 

Yes Sir, I am curious to see how you did your accessories setup. Thank you. I appreciate your knowledge.
Originally, I was going to do the 96 LT4 330 hp. swap. I have the LT-4 from a 1996 Gran Sport Vette with 90,000 miles on it. Simply because it’s a direct bolt in. As time goes on and the LS series have become more power and more popular. I’m thinking the LS would be a better choice than the 96 LT4. I’m not looking for 500 horses because my car is a highway car not a race car. I drive over 500 miles a week up and down I-35 between Kansas and Texas. After lots of research, I decided on the 2011 L9H, L94 series and 6L80. Before I invest in the engine and transmission. I want to make sure I can get all the accessories and ecm planned out. I’m also thinking the 6L80 transmission with probably a stand alone computer. I don’t want the 4L60 any more. It’s time for 200 more horsepower and 2 more gears. My 95 Impala is sporting 338,000 miles on it and it’s getting tired. My gas mileage is down to around 15.8 mpg. I believe it’s time for an implant. My LT-1 and 4L60 have never been apart. I do regular transmission fluid and engine oil changes on time.
Thanks, Jerry
I would be glad to give you my e-mail