FJ LS swap AC wiring

[BrisFJ60]

We've swapped a LS into son's cruiser with 4L60e. We are using FJ AC components and GM

compressor and had hoses modified. We can get the compressor to run by going from switch directly out to high pressure switch and into compressor wiring. The GM wiring harness omitted the AC / ECM wiring.

Is there any reason to run this wiring through the FJ amp? If so, why and how?

Any help will be greatly appreciated, thanks!

 

[LA Z]

It can be done, and it would give you an extra layer of protection.
If you run your ac without the 60s AC amplifier, wired as you described
AC button to low pressure switch ( you wrote high pressure, but I assume you talking about the switch by the evaporator ) to AC compressor clutch, would work but…..

You would have the compressor clutch full current going through the AC button and the pressure switch,
not the best idea. ( these were not designed to do that ) You should at least wire up a relay to trigger the clutch.
Also by not using the amplifier your low temperature cutout ( preventing the icing on your evaporator by utilizing the temperature sensor ) is not working.

The AC amplifier contains a relay to run the compressor clutch and wired for the low temperature cutout.
Wiring the amp. might seem a lot but I think it’s worth the time.

 

[BrisFJ60]

Great info LA Z. How would we go about wiring in the amp then out to the relay?

 

[LA Z]

I don’t have the wiring diagram for the AC amp. available right now, but I’ll get back to you with it tomorrow.
It would be a few extra wires for the temperature sensor and ignition coil, ( these are wired into the amp. in the factory wiring harness ) but I think it’s fairly easy.

 

[BrisFJ60]

That will be great. But, we are running an LS .... Not one coil, but 8

 

[dbbowen]

Are you running gen3 or gen 4 LS? You really need to bypass the fj60 amplifier completely for it to properly work. Its old technology and you really want to have your GM Computer controlling the entire AC System instead of kind of hodgepodging it together with the toyota stuff. Using the toyota amp is kind of unsafe because it does not have a high pressure switch in the system, so if you overpressure it will just dump the freon out of the relief valve on the compressor, and your GM computer wont be getting any information of the state of the AC for the rest of the operation like fans and WOT fan cut off and AC Idle speed increase.

If you are running a gen3 motor, youll need the proper PCM that has the IAC drivers to run the Air conditioning, then the rest is just wiring and having a high pressure transducer on your high pressure line. It seems like a lot but its really pretty easy to get it to work.

Ive got it all listed out at the link below for a Gen3 motor. If you do your wiring exactly like that, and follow the way i did it, then have a tuner turn the AC request to ANALOG, you can watch the function of the AC button being pressed, the computer telling the motor to idle up, the pressure transducer reading the ac pressure, and the computer telling the fans to turn on all in that order on the computer in HP Tuners. Its pretty neat

How to LS Swap a FJ60 or FJ62. Quick and dirty guide for regular folks wanting to do an engine swap in their driveway.

https://www.speedwaymotors.com/Speedway-Double-Pass-Aluminum-Radiator-Chevy,23864.html Part # 917340 This is what I got. It is a double pass and the single is like $179 or there abouts. At the bottom has the links to the shroud kits. Keep in mind this does not have a trans cooler. I prefer an...

forum.ih8mud.com

 

[BrisFJ60]

The engine is a build but primarily a Gen 3.

 

[BrisFJ60]

We put a high pressure switch in the line.

 

[dbbowen]

I just edited my post, but ill post the edit here:

Are you running gen3 or gen 4 LS? You really need to bypass the fj60 amplifier completely for it to properly work. Its old technology and you really want to have your GM Computer controlling the entire AC System instead of kind of hodgepodging it together with the toyota stuff. Using the toyota amp is kind of unsafe because it does not have a high pressure switch in the system, so if you overpressure it will just dump the freon out of the relief valve on the compressor, and your GM computer wont be getting any information of the state of the AC for the rest of the operation like fans and WOT fan cut off and AC Idle speed increase.

If you are running a gen3 motor, youll need the proper PCM that has the IAC drivers to run the Air conditioning, then the rest is just wiring and having a high pressure transducer on your high pressure line. It seems like a lot but its really pretty easy to get it to work.

Ive got it all listed out at the link below for a Gen3 motor. If you do your wiring exactly like that, and follow the way i did it, then have a tuner turn the AC request to ANALOG, you can watch the function of the AC button being pressed, the computer telling the motor to idle up, the pressure transducer reading the ac pressure, and the computer telling the fans to turn on all in that order on the computer in HP Tuners. Its pretty neat

How to LS Swap a FJ60 or FJ62. Quick and dirty guide for regular folks wanting to do an engine swap in their driveway.

https://www.speedwaymotors.com/Speedway-Double-Pass-Aluminum-Radiator-Chevy,23864.html Part # 917340 This is what I got. It is a double pass and the single is like $179 or there abouts. At the bottom has the links to the shroud kits. Keep in mind this does not have a trans cooler. I prefer an...

forum.ih8mud.com

 

[BrisFJ60]

Great info, thanks very much!

 

[dbbowen]

Great info, thanks very much!

Sure thing, if you go to the first page of that thread, theres a table of contents that is hyperlinked to the rest of the posts for easy navigation with a lot of other LS Swap topics and stuff

 

[BrisFJ60]

Son's swap is nicely completed, a very clean install. He did a body off restoration simultaneously as he waited for the Advance Adapters kit for connection to the Toyota transfer case. He also completely rebuilt the t case.

 

[dbbowen]

Son's swap is nicely completed, a very clean install. He did a body off restoration simultaneously as he waited for the Advance Adapters kit for connection to the Toyota transfer case. He also completely rebuilt the t case.

Nice thats awesome to see!

 

[BrisFJ60]

He upgraded the suspension with OME and a 6" lift. That lift made alignment more difficult and his tuner advised that he return the shackles to stock height, which we did. This made all the difference in the world and handles much better. It still has plenty of lift / clearance. 99.9% of his use is as a daily driver and not off road. The stock 6 was strong but a super gas hog. This LS sucks gas but doubles what the stock drivetrain offered.

The engine builder (friend of his) put a mild cam upgrade in and the 4L60e was freshened up. This thing sounds great and goes waaay too fast in my opinion.....but I'm an old man with a GX 470 and 4cyl 5speed GM Sonoma.

 

[adman02]

Are you running gen3 or gen 4 LS? You really need to bypass the fj60 amplifier completely for it to properly work. Its old technology and you really want to have your GM Computer controlling the entire AC System instead of kind of hodgepodging it together with the toyota stuff. Using the toyota amp is kind of unsafe because it does not have a high pressure switch in the system, so if you overpressure it will just dump the freon out of the relief valve on the compressor, and your GM computer wont be getting any information of the state of the AC for the rest of the operation like fans and WOT fan cut off and AC Idle speed increase.

If you are running a gen3 motor, youll need the proper PCM that has the IAC drivers to run the Air conditioning, then the rest is just wiring and having a high pressure transducer on your high pressure line. It seems like a lot but its really pretty easy to get it to work.

Ive got it all listed out at the link below for a Gen3 motor. If you do your wiring exactly like that, and follow the way i did it, then have a tuner turn the AC request to ANALOG, you can watch the function of the AC button being pressed, the computer telling the motor to idle up, the pressure transducer reading the ac pressure, and the computer telling the fans to turn on all in that order on the computer in HP Tuners. Its pretty neat

Apologies to OP for the hijack - @dbbowen does any of this still apply if running a mechanical fan on a Gen 3 motor?

 

[dbbowen]

Apologies to OP for the hijack - @dbbowen does any of this still apply if running a mechanical fan on a Gen 3 motor?

I think it would be mostly the same, you just wouldn’t connect up an e fan. Turning the fan on is the last thing in the chain of command in the AC sequence.

Off the top of my head if you wired everything up like in my thread and just didn’t do the fan portion and let your mechanical fan work like normal, the computer would just control idle up and cut AC at WOT.

I haven’t installed an LS with a mechanical fan, but just watching it in HP tuners in theory it would work just fine

 

[BrisFJ60]

Son's is running a mechanical fan.