The A/C Amp Thread (3 Viewers)

[TrickyT]

You don't need the idle-up VSV connected for the A/C to operate, so leaving it disconnected is fine.

Does your aftermarket ECU use +12v on its idle-up input circuit to speed up engine RPMs? If so then you can just connect this idle-up circuit to the same wire that goes from the A/C Amp to the compressor clutch (the wire on connector pin #7 in the FJ60 schematic shown in post #3 above). If the ECU uses a different voltage to increase RPMs, then you need to figure out what it expects. But 9-to-1 odds says it's +12v.

 

[60 toy ota]

yes I was planning on just putting the compressor wire to the eco for idle up.
So if the VSV circuit is open circuit the amplifier should function with the pressure switch and the thermistor connected.
I just wanted to know if it would need anything in the VSV circuit.

Nope, vsv is output only. You're good

 

[Misery86]

You don't need the idle-up VSV connected for the A/C to operate, so leaving it disconnected is fine.

Does your aftermarket ECU use +12v on its idle-up input circuit to speed up engine RPMs? If so then you can just connect this idle-up circuit to the same wire that goes from the A/C Amp to the compressor clutch (the wire on connector pin #7 in the FJ60 schematic shown in post #3 above). If the ECU uses a different voltage to increase RPMs, then you need to figure out what it expects. But 9-to-1 odds says it's +12v.

I was planning on using the Clutch Output from the amplifier to go to my ECU as a AC Request. Then Get the ECU to control the AC Clutch as it will know when I am Wide open throttle. It will also control the idle.

That's the plan.

Thank you

 

[Hamachi]

The resistor removal worked like a charm. I have a Dakota Digital tach signal generator tied into the original coil signal and it did not work. Clipped the resistor and the compressor fired right up.

Do you know if you have Needed to install a high pressure switch?

 

[MrFitzie]

Do you know if you have Needed to install a high pressure switch?

If you clip the resistor and use the Toyota A/C compressor clutch signal wire to your compressor the compressor clutch will engage (assuming the other safety checks like the Toyota low pressure switch sees appropriate pressures).

If you want to incorporate a high pressure switch for additional piece of mind you would need to figure out how it fits for your setup.

I have my LS swap working direct from Toyota A/C clutch signal to the GM compressor and it works, but I am noticing a slight dip on the RPM on initial A/C request (no dip during cycling) so I am in the process redoing the wiring to let the GM ecu control the compressor like a factory GM setup so it will handle the initial idle-up and I will be using the high pressure switch as part of the circuit because my GM compressor has one installed on the back of it.

 

[bush]

Do you know if you have Needed to install a high pressure switch?

Cant remember. I had the LS ac lines and spliced them into the 60 lines. So if there was a switch close to the compressor with wiring in the OG harness, it was retained but i dug through my pics and cant see if there is a switch there or not.

 

[bush]

If you clip the resistor and use the Toyota A/C compressor clutch signal wire to your compressor the compressor clutch will engage (assuming the other safety checks like the Toyota low pressure switch sees appropriate pressures).

If you want to incorporate a high pressure switch for additional piece of mind you would need to figure out how it fits for your setup.

I have my LS swap working direct from Toyota A/C clutch signal to the GM compressor and it works, but I am noticing a slight dip on the RPM so I am in the process redoing the wiring to let the GM ecu control the compressor like a factory GM setup so it will handle the idle-up and I will be using the high pressure switch as part of the circuit because my GM compressor has one installed on the back of it.

I did wire the signal to turn on the compressor into the ECM also so it would handle the throttle control.

 

[MrFitzie]

I did wire the signal to turn on the compressor into the ECM also so it would handle the throttle control.

I did this as well, but the initial idle up takes 5-15s and from HP Tuners I can see that 5-15s corresponds to the "ac request" signal going to Yes to the "ac clutch engaged" Yes. This only happens when you first turn the AC on not as it cycles. So its a pretty minor annoyance, but I want to incorporate the high pressure switch anyway and have some free time on my hands these days...

Edited my post above to note the idle up delay is only on initial A/C request, not cycling.

 

[Hamachi]

I did wire the signal to turn on the compressor into the ECM also so it would handle the throttle control.

Did you connect the AC dash switch button wire to the 5.3 relay then to the AC compressor clutch?
I have everything up and running except my Derale dual fan does not come on when I turn the AC on. It only comes on when the engine temp signals it to come on.

 

[bush]

Did you connect the AC dash switch button wire to the 5.3 relay then to the AC compressor clutch?
I have everything up and running except my Derale dual fan does not come on when I turn the AC on. It only comes on when the engine temp signals it to come on.

I think so but I cant exactly remember how I did it. Had it all captured for reference but I included all my wiring diagrams when I sold it.

 

[Spike Strip]

Just adding this information here (from another site) :

Toyota Land Cruiser FJ60 A/C System
When I bought my FJ60 the A/C was blowing really cold air. I mean freezing air. I didn't think too much of it until one hot day I had the A/C on in stop and go traffic. Suddenly the A/C air was warmer, and shortly after I smelled burning lining. The A/C compressor had jammed solid, and the clutch on the compressor axle was just spinning and burning. A new compressor cost me $350, along with a $20 receiver/drier and $500 to have Gary's Auto install these, flush the R12 from the system, convert fittings to R134A, and refill with R134A. This is a pretty big outlay so I decided to check and make sure that the electronic control systems were operating correctly. They were not - the A/C compressor was never disengaging if the A/C button on the dash was depressed. A quick check in the manual shows the schematic of the control circuit:

The logic is provided by the "A/C Amplifier" at the bottom of the schematic. This is a small PCB inside a plastic case located just under the passenger side dashboard. The 9 pins on the PCB are as follows:

Pin	Function
1	NC
2	V+ 12VDC from A/C switch
3	V+ 12VDC switched by low pressure A/C - off if pressure less than 2.1
4	Idle up VSV (output)
5	Ignition coil signal (input)
6	Chassis ground
7	Compressor magnetic clutch (output)
8	Evaporator Thermistor (input)
9	NC

The pins can easily be seen on a front view of the amplifier board:

The blue knob protrudes through the plastic housing and is used to adjust the engine RPM at which the A/C amplifier will cut off the compressor on low idle, and also engage the compressor after idle-up is accomplished with the VSV. The red knob adjusts the temperature at the evaporator at which the compressor will be turned off to avoid evaporator freezing (factory target is about 34F). By attaching a voltmeter between pins 6 and 8, you can monitor the voltage drop across the thermistor. On mine, the voltage ranges from about 1.5V (80F ambient) to around 2.1V at 32F when the evaporator begins to freeze. By measuring this I could see that the thermistor was properly measuring the temperature of the evaporator. But the compressor just stayed engaged at all times, even after freezing occurred. I adjusted the red knob and was able to switch the VSV on/off as the amplifier attempted to turn off the system, but the clutch never disengaged - pin 7 remained high telling the compressor to run. Left as is, this would burn out my new compressor. I pulled the amplifier all the way out and examined it more closely. Lo and behold here is what I found on the reverse side of the PCB:

Somebody had modified the board, adding a jumper (circled in yellow above). The jumper connects the collector of the switching transistor to V+, engaging the clutch relay (middle of the PCB) at all times. I removed the jumper and the system began to work somewhat as intended, cycling the clutch. Here's what the back of the PCB should look like, without the jumper:

Since I had disturbed the red and blue knobs, I needed a procedure to adjust them. Here's what I came up with, since the manual doesn't tell you how to adjust the red knob:

1. Turn the blue knob fully CCW, and set the red knob to midway.
2. Run the engine with doors closed, windows up, and A/C on recirculate, low fan speed. If the compressor does not engage, slowly turn the red knob CW until you hear idle up (engine RPM goes to 900 or so) and the compressor engages.
3. Open the hood, and look at the lines going to the compressor. The compressor should disengage before the return line begins to form frost on the outside. Turn the red knob CCW to disengage the clutch when the temperature is still too high to form frost. This may take patience while you adjust a bit at a time, wait for a few cycles, and adjust again.
4. Once the red knob is set OK, turn the blue knob CW a bit at a time, listening for the compressor cycling. The compressor should engage a moment or two after the idle-up happens. Keep advancing the blue knob to reduce this delay until the compressor kicks in just after the idle-up.
5. Close up and replace everything you took off to get at the A/C amplifier.

Toyota Land Cruiser FJ60 Air Conditioning

 

[FJ60 guy]

View attachment 2496127

Thought I'd throw this in for reference.'
I just realized someone else already posted this schematic.

 

[klinetime574]

My A/C has been freezing up. I replaced the amplifier many moons ago and never paid attention the the red knob. Ever since moving to Illinois from Texas my A/C hasn’t worked as well. Sounds like I need to try this red knob. Thanks for sharing this info

 

[FJ60 guy]

Is the thermistor built into the evaporator or separate. Did you have to buy a thermistor? if so what did you use and where did you mount it?

 

[coultl]

Thank you for this! I was about to add a resistor in line with my thermistor because it’s cutting out too early. Now I know I just need to adjust the red pot!

 

[Richfj60]

Hi All,
Resurrecting an old thread because i would like to fix how my AC is wired up. I have an LS 5.3 conversion in my 88 FJ62. I have tried to decipher all of this info, but struggling. My Compressor clutch is currently wired directly to the AC on/off button, bypassing the AC Amp. The system was freezing up and has not been ideal. So, I'd like to fix. Anyway, my question is this- If I want to rewire and get functioning properly, should I bring the compressor clutch to the Pin 7 location and take Pin 2 to the on/off switch? I can't tell, but I do not see a tach connection. I think the Thermistor is still wired up. Is there anything else to get it connected to the LS?? I don't see mention of the resistor for the 62.

 

[FJ60Cam]

Hi All,
Resurrecting an old thread because i would like to fix how my AC is wired up. I have an LS 5.3 conversion in my 88 FJ62. I have tried to decipher all of this info, but struggling. My Compressor clutch is currently wired directly to the AC on/off button, bypassing the AC Amp. The system was freezing up and has not been ideal. So, I'd like to fix. Anyway, my question is this- If I want to rewire and get functioning properly, should I bring the compressor clutch to the Pin 7 location and take Pin 2 to the on/off switch? I can't tell, but I do not see a tach connection. I think the Thermistor is still wired up. Is there anything else to get it connected to the LS?? I don't see mention of the resistor for the 62.

An FJ62 amp does not require modification to work. If you can return the wiring back to factory and use the old compressor clutch wire to the GM compressor (and add a ground, if needed), then it should work as originally designed.

 

[Richfj60]

An FJ62 amp does not require modification to work. If you can return the wiring back to factory and use the old compressor clutch wire to the GM compressor (and add a ground, if needed), then it should work as originally designed.

Thanks Cam!!! Now just need to figure out where they bypassed the old wiring. It looks like it's intact except for the wire that goes directly to the on off switch. I wonder why they bypassed it all. Mysteries of a 62 built by a PO.

 

[BigHighBlue]

Glad to have found this thread. Recently my A/C quit blowing as cold as it once did so I took it to the local shop to have it looked at and recharged. They evacuated and refilled the system. According to them when they went to test the system the compressor wouldn't turn on. I find this very suspicious since it was turning on fine before I dropped it off and from what I understand it would have needed to be on to recharge. According to them they did some diagnostics and determined that it was the A/C Amplifier that was faulty. They verified this by swapping with another 60 they had in the shop and according to them it worked great. So, they found a used one that they wanted to charge me $375 for!!!!! I took my truck back and am now trying to go through the FSM to verify operation of all of the other parts before shelling out the cash for a new amp. Thanks to everyone on here for the knowledge and leg work to provide the excellent intel!

 

[Spike Strip]

@BigHighBlue

Contact @Engineer8000 He can fix your A/C Amp board (Service he offers) and has the components to do so.

Emissions Computer 89550-60130

I spent some time in the shop reverse engineering this module and drew up the schematics for the different functions. It has two proprietary ICs on it, one that handles RPM and one that handles the speed sensor and temperature sensor. These turn various transistors on and off to perform the...

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