Question about an AC Amplifier- 83 FJ60 (1 Viewer)

[John Staton]

Just to close this one out....I could not see any obvious problems with amy AC amplifier and it was diagnosed as a bad AC amplifier by a process of elimination. I want ahead and picked up 2 from folks that were parting out trucks for $50 buck a piece. It was swapped and AC is running great again. Charged it with dye so if I do have a leak I will know where it is...but back to blowing cold again.

 

[John Staton]

Blowing cold but I have a questions about tuning the AC amplifier. My AC will cool down to where it should. I have a thermometer stuck in one of the vents so I can monitor how cold the air is coming out. Sometimes when I come to a stop I notice the temperature of the air start to rise. If I sit there long enough I have seen it go from the 40s to the 60s before I start moving. I assume that maybe the idle is telling the compressor to sit tight until I start rolling again and get the idle up. I dont have any issues with my idle when I am at a stop...AC or no AC. It idles how it should around 650-700. I am pretty sure this is what is going on as when I was out last night and saw it happening I revved up the engine a bit and the temp made a 180 and started getting colder again.

So my question- is the nob on the top of the AC amplifier that sticks out a way to fine tune this behavior?? Can I turn it one way and keep this from happening at every stop??

 

[tmxmotorsports]

You maybe able to adjust by tge knob i have a 62 when i turn on the ac the truck idles up doesn't stay the same

 

[John Staton]

what is the effect of turning the AC amplifier nob clockwise and counterclockwise?? I am desmogged and replaced it and even though I am blowing cold when driving, the compressor seems to stop when I am stopped causing the temp to rise until I get going again.

 

[Thornton Melon]

what is the effect of turning the AC amplifier nob clockwise and counterclockwise?? I am desmogged and replaced it and even though I am blowing cold when driving, the compressor seems to stop when I am stopped causing the temp to rise until I get going again.

I was just messing with this today.
I do not have an ac idle up attached to my carb and the compressor was a little too eager to kick off at idle which is around 650.
I did lower the knob, towards low, a bit and then would blip the throttle after. After a quick “blip” the compressor would engage. I raised the knob towards the high as much as I could to where a little throttle would kick on the compressor. I then drove it around for about 20 mins with great cooling affects. I had never felt so nice at a light. No freezing. And it’s hot and humid in Dallas today.

 

[John Staton]

I was just messing with this today.
I do not have an ac idle up attached to my carb and the compressor was a little too eager to kick off at idle which is around 650.
I did lower the knob, towards low, a bit and then would blip the throttle after. After a quick “blip” the compressor would engage. I raised the knob towards the high as much as I could to where a little throttle would kick on the compressor. I then drove it around for about 20 mins with great cooling affects. I had never felt so nice at a light. No freezing. And it’s hot and humid in Dallas today.

so you turned the nob clockwise? I think that is what I read from another post to make it kick on at a lower RPM

 

[Thornton Melon]

Yes, I believe clockwise is correct. There should be a “high”/“low” mark on the casing. Clockwise being low to the best of my recollection.

 

[Gretsch]

Not to hi-jack here, but is the AC amplifier the sort of part that could be simply re-created somehow by maybe an electronics shop or something? Seems like this is pretty low tech compared to todays standards, someone who knew what they were doing could re-create something like this without too much trouble or expense. I am not that person so maybe I am way off here. If specialty parts like these (or say the emissions control board) could be recreated, I know I would feel better about the feasibility of keeping my stock truck on the road for years to come. Most folks would simply move on to a engine transplant to be able to maintain these trucks more easily. But since these trucks are relatively low tech to begin with, wondered about how hard it would be to recreate these sorts of specialty parts in an effort to keep the stockers on the road.

 

[Thornton Melon]

This was part of my reading last night as I tried to understand why my ac wasn’t working anymore. (Turns our that aftermarket tach still needs to plug into the original system for the ac amplifier to supply power to the compressor)
But this post was incredibly interesting and incredibly over my head.

The A/C Amp Thread

This thread is all about FJ60/FJ62 A/C amplifiers. You know, that little black box that mounts on the evaporator case behind the glove box. There are plenty of other threads concerning A/C amps and I thought about adding to those, but in the end decided that the information here breaks enough...

forum.ih8mud.com

 

[cps432]

Has anyone thought to replace the capacitors in the old failed units? Caps tend to last a decade or so depending on how they’re constructed. They cost pennies. It’s a worthy experiment. Heck, you can de-solder them and test them out of the circuit to see if they’re in tolerance. It looks like everything else on that board should last indefinitely other than the caps. Resistors sometimes fail but not as often.

 

[Gretsch]

This was part of my reading last night as I tried to understand why my ac wasn’t working anymore. (Turns our that aftermarket tach still needs to plug into the original system for the ac amplifier to supply power to the compressor)
But this post was incredibly interesting and incredibly over my head.

The A/C Amp Thread

This thread is all about FJ60/FJ62 A/C amplifiers. You know, that little black box that mounts on the evaporator case behind the glove box. There are plenty of other threads concerning A/C amps and I thought about adding to those, but in the end decided that the information here breaks enough...

forum.ih8mud.com

Well as usual someone on Mud has already done something I was thinking.

So with that thread maybe you could just take the schematic to an EE and have him build one. Great info and thanks for sharing.