The A/C Amp Thread (2 Viewers)

[jebb]

Excellent post

 

[BurntToast]

Trying to get the AC sorted on my 88 FJ62. I am knee deep in my dash and have some questions. After a lot of study I have a plan, but still some questions. If you look at my notes (see pictures below), the current set up bypasses the AC Amp, by wiring the AC switch directly to the AC clutch. It currently does not have the thermistor or pressure switch active. The proposed set up is to wire the output of the AC Amp directly to the AC clutch (original set up on a FJ62 goes through the ECU). Then add a high pressure switch to the ground side of the GM Compressor. That much is straightforward, but is it correct? Also, the Ignition wire to the AC Amp (the Black/white wire) is missing. While cleaning up the harness, I found an "unused" (post swap) Black/white 10Ga wire. Can I use that one? View attachment 3605683View attachment 3605684View attachment 3605685

I am in the same boat, and was thinking along the lines you had there. BP has a nice drier with the pressure sensor for the GM computer to idle up and the binary for compressor protection

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

 

[Richfj60]

I am in the same boat, and was thinking along the lines you had there. BP has a nice drier with the pressure sensor for the GM computer to idle up and the binary for compressor protection

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

From what I read, only select ECUs take the on/off signal from the button. I unfortunately do not have one of those ECUs. So, I won't have Idle up, but that hasn't been an issue in the past.

 

[BurntToast]

From what I read, only select ECUs take the on/off signal from the button. I unfortunately do not have one of those ECUs. So, I won't have Idle up, but that hasn't been an issue in the past.

My assumption was (good or bad) was that the pressure tap to most computers dealt with the idle up. Which ECM are you running?

 

[Richfj60]

My assumption was (good or bad) was that the pressure tap to most computers dealt with the idle up. Which ECM are you runnin My PCM is 12586242 and isn't on the list that accepts a physical AC on request. So I have to control my AC the old fashioned way. No idle up. And physically wired to the binary switch

My assumption was (good or bad) was that the pressure tap to most computers dealt with the idle up. Which ECM are you running?

My PCM is 12586242 and isn't on the list that accepts a physical AC on request. So I have to control my AC the old fashioned way. No idle up. And physically wired to the binary switch. The physical request is the blue on/off button.

 

[BurntToast]

My PCM is 12586242 and isn't on the list that accepts a physical AC on request. So I have to control my AC the old fashioned way. No idle up. And physically wired to the binary switch. The physical request is the blue on/off button.

Ah for some reason I assumed you had a newer setup

 

[Richfj60]

Ah for some reason I assumed you had a newer setup

2004 L59 5.3. The newer PCM is the issue. My understanding is that if the LC doesn’t have a digital on/off signal to the PCM, it won’t work. I’m no expert, just learning by necessity. If you learn something else, let me know

 

[Richfj60]

Update. Some success, more questions....I hooked up the ignition wire to the spade terminal on the AC Amp. Turned on the key and pushed the blue button and had power to the wire that goes to the AC compressor. Unfortunately it didn't shut down when a turned off the blue button. Note- All of the wires were not hooked up the AC Amp, there was a ground and another wire- I think it was the on/off button. Maybe the default is that the AC is on? Is the switch internal to the AC amp? The good news is that I am getting power through the AC amp to the wire that goes to the compressor, bad news is that it won't shut off.

 

[TrickyT]

Update. Some success, more questions....I hooked up the ignition wire to the spade terminal on the AC Amp. Turned on the key and pushed the blue button and had power to the wire that goes to the AC compressor. Unfortunately it didn't shut down when a turned off the blue button. Note- All of the wires were not hooked up the AC Amp, there was a ground and another wire- I think it was the on/off button. Maybe the default is that the AC is on? Is the switch internal to the AC amp? The good news is that I am getting power through the AC amp to the wire that goes to the compressor, bad news is that it won't shut off.

It may be good for you to go back at look at the first few posts in this thread. The purpose of the Ignition terminal on the A/C amp in the FJ62 is to inhibit the compressor from engaging during engine start-up. That's because of the feeble 150HP produced by the "mighty" 3FE. ("Mighty" compared to the 125HP 2F in the FJ60.) A 300+ HP Vortec could care less about the A/C compressor engaging or not during start-up. So the "1) prevent compressor from engaging during engine start-up" discussed in Post #1 does not really apply after a V8 swap. More importantly, in your situation, the A/C amp will inhibit the compressor from running if the evaporator thermistor thinks thinks the evaporator coils are getting close to freezing. This is still an important function of the A/C amp in your post-swap vehicle. If you hook up your compressor, pressure switch, and thermistor as shown in the FJ62 wiring diagram in Post #3 and just leave the Ignition spade lug on the A/C amp disconnected you should be good to go.

 

[Richfj60]

It may be good for you to go back at look at the first few posts in this thread. The purpose of the Ignition terminal on the A/C amp in the FJ62 is to inhibit the compressor from engaging during engine start-up. That's because of the feeble 150HP produced by the "mighty" 3FE. ("Mighty" compared to the 125HP 2F in the FJ60.) A 300+ HP Vortec could care less about the A/C compressor engaging or not during start-up. So the "1) prevent compressor from engaging during engine start-up" discussed in Post #1 does not really apply after a V8 swap. More importantly, in your situation, the A/C amp will inhibit the compressor from running if the evaporator thermistor thinks thinks the evaporator coils are getting close to freezing. This is still an important function of the A/C amp in your post-swap vehicle. If you hook up your compressor, pressure switch, and thermistor as shown in the wiring FJ62 diagram in Post #3 and just leave the Ignition spade lug on the A/C amp disconnected you should be good to go.

Thanks TrickT so much information that it’s hard to keep it all straight. I’ll disconnect the spade and see if it works. Thank you very much!!!

 

[TrickyT]

Thanks TrickT so much information that it’s hard to keep it all straight. I’ll disconnect the spade and see if it works. Thank you very much!!!

You still need the original FJ62 wiring attached to the A/C Amp: i.e., the blue dash switch, the compressor clutch, the pressure switch, and the thermistor. Everything except the ignition wire from the FJ62 ECU.

 

[Richfj60]

You still need the original FJ62 wiring attached to the A/C Amp: i.e., the blue dash switch, the compressor clutch, the pressure switch, and the thermistor. Everything except the ignition wire from the FJ62 ECU.

When I was tracing out the lines, I found the AC Comp clutch wire went to the plug for the ECU. The wire to/from the AC Amp was in another location. I pulled the wire out of the ECU plug and was going to connect it to the pigtail to/from the AC amp. That way I'd be bypassing the plug and the output of the amp would go directly to the compressor clutch. It looks like someone tried to play with the wiring before me, but I've replaced the low press switch and thermistor when I rebuild my evaporator box. Hopefully it all works now and can function properly. I intend to add a high press switch on the ground side of the compressor for added protection.

 

[884runner]

The blue knob on my AC amp is missing and a PO has a wire coming out of that hole and grounded it to the body under the dash. I am not an EE, so does this make any sense? I don't know if that maximizes the knob or minimizes the knob or makes the amp not work at all? Just wondering if anyone knows since new amps are not readily available.

 

[TrickyT]

The blue knob on my AC amp is missing and a PO has a wire coming out of that hole and grounded it to the body under the dash. I am not an EE, so does this make any sense? I don't know if that maximizes the knob or minimizes the knob or makes the amp not work at all? Just wondering if anyone knows since new amps are not readily available.

Impossible to know the answer without first determining where the blue wire connects to on the circuit board.

 

[884runner]

Impossible to know the answer without first determining where the blue wire connects to on the circuit board.

That makes sense. I wasn’t home when I sent the message and before I read this thread I didn’t know the board could be pulled out etc. The ground wire goes to the center spool of copper (clutch?). Is there a good reason why a PO would want to run a ground to there? I also seem to have the same board as in post #25 being maybe the first version of these. The knob doesn’t seem to protrude from the cover, maybe on purpose. Also based on your marks for the red dial mine may be set too cold? I think my main problem with my ac may be trash in the system so I’m going to take it apart and clean it out. Everything is new except the condenser and low pressure switch and the hoses. I’m going to get a new low pressure switch and clean everything out and reassemble. But that wire coming out of the amplifier never looked right to me.

 

[TrickyT]

That makes sense. I wasn’t home when I sent the message and before I read this thread I didn’t know the board could be pulled out etc. The ground wire goes to the center spool of copper (clutch?). Is there a good reason why a PO would want to run a ground to there? I also seem to have the same board as in post #25 being maybe the first version of these. The knob doesn’t seem to protrude from the cover, maybe on purpose. Also based on your marks for the red dial mine may be set too cold? I think my main problem with my ac may be trash in the system so I’m going to take it apart and clean it out. Everything is new except the condenser and low pressure switch and the hoses. I’m going to get a new low pressure switch and clean everything out and reassemble. But that wire coming out of the amplifier never looked right to me.

View attachment 3897552

View attachment 3897553

With that wire in place the clutch on the A/C compressor will be engaged whenever the A/C dash switch is on, as long as there's enough Freon in the system. (The wire effectively by-passes most of the circuitry on the board so that the relay open and closes based on the position of the dash switch.)

 

[884runner]

With that wire in place the clutch on the A/C compressor will be engaged whenever the A/C dash switch is on, as long as there's enough Freon in the system. (The wire effectively by-passes most of the circuitry on the board so that the relay open and closes based on the position of the dash switch.)

Wow, Thanks for the help. I will probably disconnect that wire from ground and try to run the board as intended and go from there.

 

[TrickyT]

Wow, Thanks for the help. I will probably disconnect that wire from ground and try to run the board as intended and go from there.

Happy to help. I think it would be good to disconnect that added wire if you can as it bypasses the temperature sensor located near the evaporator. That sensor is designed to shut off the compressor when the evap coils get close to freezing over, so without that protection the compressor will just keep running as long as the dash switch in on. Clearly the PO was trying to fix some problem with the A/C system, but the bypass wire didn't address the real problem and is only a makeshift solution to avoid troubleshooting the basic issue.

 

[884runner]

Happy to help. I think it would be good to disconnect that added wire if you can as it bypasses the temperature sensor located near the evaporator. That sensor is designed to shut off the compressor when the evap coils get close to freezing over, so without that protection the compressor will just keep running as long as the dash switch in on. Clearly the PO was trying to fix some problem with the A/C system, but the bypass wire didn't address the real problem and is only a makeshift solution to avoid troubleshooting the basic issue.

Thanks again. One last question, would it also bypass the low pressure switch? Or would that switch still be able to turn off the compressor even with this?

 

[TrickyT]

Thanks again. One last question, would it also bypass the low pressure switch? Or would that switch still be able to turn off the compressor even with this?

Nope; doesn't bypass the low pressure switch.