Question about an AC Amplifier- 83 FJ60

[John Staton]

So looks like mine has a problem. I have read about this part and as I understand it, its main job it to engage and disengage the compressor clutch based on the idle speed. I was considering just bypassing it until I get another one and was wondering if there would be any problems in doing this. Will my compressor still cycle on and off like is should so it doesn't freeze up. Is that controlled by something else?

 

[FJ40Jim]

The AC amplifier is a small computer that turns on & off the compressor and the AC idle up solenoid using inputs from temp, pressure, RPM, etc.

By passing it will result in a compressor that is on constantly, no cycling based on temp input.

 

[John Staton]

The AC amplifier is a small computer that turns on & off the compressor and the AC idle up solenoid using inputs from temp, pressure, RPM, etc.

By passing it will result in a compressor that is on constantly, no cycling based on temp input.

so short term solution only is what you are saying??

 

[FJ40Jim]

Yes, very short term. On a humid day the evaporator will freeze in in 10-15minutes, then the system will need shut off for a while to let the ice melt and restore airflow through the evap.

 

[Bama4door]

The AC amplifier is a small computer that turns on & off the compressor and the AC idle up solenoid using inputs from temp, pressure, RPM, etc.

By passing it will result in a compressor that is on constantly, no cycling based on temp input.

Is the amplifier still an available part from Toyota or even aftermarket?

 

[FJ40Jim]

Amplifier is a 88650-60020 . Long discontinued.
Cruiserparts.net shows used ones available for a reasonable price.

 

[John Staton]

Amplifier is a 88650-60020 . Long discontinued.
Cruiserparts.net shows used ones available for a reasonable price.

I hate that website...is there no way to do a search?? How much is it listed for?? I am curious. I found one from someone who is parting out and it looks almost identical but has a different part number than the one that come off of mine...it is pictured below, mine is in the beginning of the post:

 

[boots4]

On mine I bypassed the idle function (kills the blue knob function) and left the temp part intact. It cycles the compressor based on temperature based on the setting of that red knob on the board. I did this because I did an engine swap and don't have the idle signal for the board to process. There is a thread in the 60 section that tells you which resistor to remove and that's what I followed.

 

[FJ40Jim]

Cruiserparts.com listing

 

[John Staton]

On mine I bypassed the idle function (kills the blue knob function) and left the temp part intact. It cycles the compressor based on temperature based on the setting of that red knob on the board. I did this because I did an engine swap and don't have the idle signal for the board to process. There is a thread in the 60 section that tells you which resistor to remove and that's what I followed.

Thanks...I will search for it.

 

[FJACS]

Thanks...I will search for it.

What diagnosis lead to determining the amplifier is faulty?

 

[tmxmotorsports]

What diagnosis lead to determining the amplifier is faulty?

Did you make sure there areno blown fuses in your other thread your compressor was working then it stopped.

 

[John Staton]

Did you make sure there areno blown fuses in your other thread your compressor was working then it stopped.

honestly, I have it at a shop. The air was blowing when the compressor stopped working...I heard it stop while I was driving and watched the temp start going up on the gauge I have stuck in the vent. I know the shop hooked the compressor up direct and it worked. As far as fuses go, I am assuming the one that runs the blower runs the compressor too?

 

[tmxmotorsports]

honestly, I have it at a shop. The air was blowing when the compressor stopped working...I heard it stop while I was driving and watched the temp start going up on the gauge I have stuck in the vent. I know the shop hooked the compressor up direct and it worked. As far as fuses go, I am assuming the one that runs the blower runs the compressor too?

Yes

 

[John Staton]

Yes

Ok, thanks...that what I thought and rules out the fuse.

 

[Dr. John]

Well.....No.....The blower circuit is fused separately from the amplifier /compressor clutch circuit. If the blower works but no compressor engagement, check the 10 amp AC fuse in the fuse panel (Upper right hand corner of attached schematic). Jumper the yellow and black/white wires at the amplifier plug, to bypass the amplifier. If the compressor clutch still doesn't engage, the problem is not the amplifier.

 

[tmxmotorsports]

When i said yes ment yes fused separate

 

[sims]

On mine I bypassed the idle function (kills the blue knob function) and left the temp part intact. It cycles the compressor based on temperature based on the setting of that red knob on the board. I did this because I did an engine swap and don't have the idle signal for the board to process. There is a thread in the 60 section that tells you which resistor to remove and that's what I followed.

Your solution made me think that in order to replace the amplifier one could possibly use a universal thermostatic control switch to cycle the compressor and kick in the fast idle solenoid. Has anyone tried this? My amplifier is intermittent and I'm redoing my A/C and I figure I may go with the thermostat. I'll see what's involved in the evaporator. I'll look for the resistor thread.

SimS

 

[FJACS]

Here’s a good 101 on how various inputs are used to control the compressor.

https://www.factoryairtemp.com/Upload/Factory%20Air/documents/Tech%20Tips/FA4S%20358%20AC%20AMPLIFIER-BELT%20LOCK%20CONTROLLER.PDF

As our trucks get older and these continue to fail, finding a newer retrofit might be worth investigating.

 

[John Staton]

Here’s a good 101 on how various inputs are used to control the compressor.

https://www.factoryairtemp.com/Upload/Factory%20Air/documents/Tech%20Tips/FA4S%20358%20AC%20AMPLIFIER-BELT%20LOCK%20CONTROLLER.PDF

As our trucks get older and these continue to fail, finding a newer retrofit might be worth investigating.

Yeah, if anyone has maybe done something different maybe they will share. I picked up a couple of extra ones from folks parting out so I would have a spare.