V8 swap ac question.

[AcroSteve]

I'm completely abandoning the factory AC amplifier and just using the ac switch and the low pressure switch but I haven't noticed anyone mention the thermostat in the ac evaporator.

Is there any preferred method when changing a 60 over to GM v8? I believe there are 3 wires on the t-stat. Just find the NC pair and use them and run in series with the LP switch?

Thanks.

 

[BurntToast]

Not sure if you can just add it in the circuit.

The A/C Amp Thread

forum.ih8mud.com

Some good info in there about removing the 60s rpm limiter. I think if you do that you can use the amp as is?

 

[tmxmotorsports]

I'm completely abandoning the factory AC amplifier and just using the ac switch and the low pressure switch but I haven't noticed anyone mention the thermostat in the ac evaporator.

Is there any preferred method when changing a 60 over to GM v8? I believe there are 3 wires on the t-stat. Just find the NC pair and use them and run in series with the LP switch?

Thanks.

Use the ac amplifier it's easy.

 

[AcroSteve]

Not sure if you can just add it in the circuit.

The A/C Amp Thread

forum.ih8mud.com

Some good info in there about removing the 60s rpm limiter. I think if you do that you can use the amp as is?

Amp is in a state of disfunction anyway. It has been bypassed for some time now.

 

[AcroSteve]

Use the ac amplifier it's easy.

Well, there's something wrong with mine already, and I'm not buying one just to have it.

 

[tmxmotorsports]

Amp is in a state of disfunction anyway. It has been bypassed for some time now.

I may have one.

 

[tmxmotorsports]

You need it to control the ac system

 

[AcroSteve]

I may have one.

I'm not sure the benefits with a more powerful v8. Besides, the ac switch goes through the v8 computer controller. It's handling the clutch duties.

I'm just looking for compressor protection and avoiding potential freeze ups.

 

[AcroSteve]

You need it to control the ac system

Not sure that I do.
maybe I'm not thinking of something you have specific knowledge of.

May I ask why I would need it?

 

[tmxmotorsports]

I'm not sure the benefits with a more powerful v8. Besides, the ac switch goes through the v8 computer controller. It's handling the clutch duties.

I'm just looking for compressor protection and avoiding potential freeze ups.

That's what it does

 

[AcroSteve]

That's what it does

But it's overkill, what with the vsv and speed sensing stuff.

Without the factory tach, it won't know the engine speed. And without a vsv, it won't idle the engine up.

I guess I'm answering my questions myself. In all my experiences with ac systems on various caterpillar construction equipment, there's a hot wire that passes through some switches before it energizes the compressor clutch. Those switches usually being at least a low pressure switch. But in some cases a high pressure switch also. My primary question was the oem thermostat, as it's been many long years since I worked on those previously mentioned systems.

Surely we can limit our conversation to that specific component.

Remembering now, when I installed the heater/ac box, the end of the thermostat was close, but not touching the evaporator. Should it actually be in contact with it for proper function? And how does it function? Is it simply a set of NO / NC contacts?

 

[BurntToast]

I used this to house those pressure sensors

LS Swap Receiver Drier with GM A/C Pressure Transducer

Complete LS Swap A/C Receiver Drier with GM Pressure Transducer for your LS Swap. Get your A/C working just like a LS equipped vehicle! No more stalling!

bp-automotive.com

Hi lo cutoff in line with the clutch, the other sensor goes to the ECU for idle up. The AC Amp still provides the evap protection

 

[tmxmotorsports]

The Amp once modified will not use the tach function also will not idle up the gm ecm will idle up slightly when it feels the load.and there isn't a high pressure switch only low and the thermo coupling

 

[tmxmotorsports]

I used this to house those pressure sensors

LS Swap Receiver Drier with GM A/C Pressure Transducer

Complete LS Swap A/C Receiver Drier with GM Pressure Transducer for your LS Swap. Get your A/C working just like a LS equipped vehicle! No more stalling!

bp-automotive.com

Hi lo cutoff in line with the clutch, the other sensor goes to the ECU for idle up. The AC Amp still provides the evap protection

I haven't used this

 

[dbbowen]

If you are using a Gen3 LS Based motor you can just run it all through the GM computer. This doesnt work on gen4 or LT FYI


The Gen 3 system doesnt use a temp switch, it uses the low pressure switch to sense the pressure dropping and cuts the compressor. The AC System should cycle on and off during its operation based on high and low freon pressure using a low pressure switch and a high pressure transducer on the high pressure line near the compressor. Theres multiple ways to get this to work honestly.

Youll need a few things to get it to work.

-proper PCM with IAC Drivers
-High pressure transducer or high pressure switch (depending on which pcm AC Request criteria you use in your tune, analog or analog cycling)
-Low pressure switch in your evaporator
-if you have electric fans, a wire from the wiring harness of your Efans that allows an external on/off switch


The rest is just wiring it. Youll bypass the land cruiser amplifier and control the whole AC System through the GM PCM. If you do it right it will cycle the ac on and off based on pressure, bump your idle up when you press the AC button on your dash, protect against high/low pressure spikes, cut the compressor at WOT, and if you have Efans, cut your fans on and off during cycling and if the compressor isnt on.

 

[tmxmotorsports]

If you are using a Gen3 LS Based motor you can just run it all through the GM computer. This doesnt work on gen4 or LT FYI


The Gen 3 system doesnt use a temp switch, it uses the low pressure switch to sense the pressure dropping and cuts the compressor. The AC System should cycle on and off during its operation based on high and low freon pressure using a low pressure switch and a high pressure transducer on the high pressure line near the compressor. Theres multiple ways to get this to work honestly.

Youll need a few things to get it to work.

-proper PCM with IAC Drivers
-High pressure transducer or high pressure switch (depending on which pcm AC Request criteria you use in your tune, 12v or 12v cycling)
-Low pressure switch in your evaporator
-if you have electric fans, a wire from the wiring harness of your Efans that allows an external on/off switch


The rest is just wiring it. Youll bypass the land cruiser amplifier and control the whole AC System through the GM PCM. If you do it right it will cycle the ac on and off based on pressure, bump your idle up when you press the AC button on your dash, protect against high/low pressure spikes, cut the compressor at WOT, and if you have Efans, cut your fans on and off during cycling and if the compressor isnt on.

I need to start doing my own engine harness so many functions get bypassed by my current harness guy.

 

[dbbowen]

I need to start doing my own engine harness so many functions get bypassed by my current harness guy.

Man, yeah i had to add pretty much all of this to my painless harness. The only company i know that includes the high pressure transducer wiring is BP Automotive for the LS stuff.

The AC Request is in most harnesses, but youll have to do the low pressure switch wiring. To completely bypass the amplifier, you can wire the gm pcm pinout for low pressure switch straight to ground. Then wire your toyota low pressure to a relay and the other side of the relay to the black/white wire from the AC Amp connector for compressor +. The coil side will get ground from the gm pcm pin 43 of the green connector.

Transducer is just wired like factory to the PCM

This is how i did it. I just put the relay behind the glove box. In your tune you need to set the AC Request criteria to Analog.

I will say. My evaporator does still freeze though. If you do it this way i dont think youll have the anti freezing protection like the factory GM low pressure switch since i just put my low pressure switch GM Pinout straight to ground. My evaporator has only freezed twice on me and it was both at about 3 hours into a road trip with the AC on full blast the whole time. In the circuit i made, im using the low pressure switch to control the compressor. There are a few other ways to set this up and it still work.

I think the fix for my setup would be to add a gm low pressure switch somewhere on mine and wire the ground for the pcm to it but im too lazy to get around to it. I mainly did my AC the way its set up now because the FJ60 in factory setup doesnt have a high pressure cut off switch. It will literally shoot freon out the back of the compressor if the pressure gets too high, trust me hahah

 

[tmxmotorsports]

Using the ac amplifier is pretty straightforward/ easy you loose idle up and ac compressor wide open throttle no freezing up and it cycles as normal that said engine still idles up a little but hasn't been an issue.

 

[dbbowen]

Using the ac amplifier is pretty straightforward/ easy you loose idle up and ac compressor wide open throttle no freezing up and it cycles as normal that said engine still idles up a little but hasn't been an issue.

when i used the ac amp i had issues with high pressure spikes and it would burp freon out of the compressor, that being said, i might have messed something up my first go round haha

 

[AcroSteve]

If you are using a Gen3 LS Based motor you can just run it all through the GM computer. This doesnt work on gen4 or LT FYI

Well, I'm using an L8T. So most of the rest of that post doesn't apply.

My harness connects to the gm ac compressor. I'm not sure, but I think there is also a high pressure switch on the back of tge compressor(I'm out of town). And just a signal wire for ac activation that comes from the chassis. I'll be doing a variation on your schematic. But it's rather similar.

I'm not sure how the ecm was programed to react to the ac, but I do have a tuner program(hp tuner) to access it, but haven't gotten my feet wet with any of that yet. And I'm still a day or 100 before I'll have it drivable.