24V AC Amplifier

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Interesting to note, this a/c amplifier does not have an "idle up" function. How is that handled with the diesels, or is it not required? The idle up is handled by the ECU in the FJ62, no VSV required.
 
This picture that you posted, it looks like the plug is wired like an FJ60, except for that Y/B wire in #8 position.

1647022614848.webp


1647022806364.webp
 
My 4 cylinder diesel idles roughly, as in shakes the truck, so I increase the idle rpm with the hand throttle. When the ac kicks in the rpm's drop a bit so I adjust by hand again. Since my ac is currently controlled only by a dash switch, this manual method is no big deal.
 
Here's some pics of the connector + wiring diagram from the FSM.

I may need to do some more digging, it looks like the as-built harness color(s) do not match up with the codes in the FSM or I do not understand the FSM codes.

Harness:
1. Black
2. White/black
3. Black/white
4. Yellow/black
5. White/blue

6. [empty]
7. Yellow
8. Yellow/green
9. Blue/black

PXL_20220315_002739986_2.jpg


PXL_20220315_020134194_2.jpg


PXL_20220315_020147596_2.jpg
 
Last edited:
Typically the fj60 connector is numbered like this

1647350808826.png


Your harness sort of matches up with the FJ60 harness for the AC amp. The AC amp sub harness connects to another connector (#4 on this diagram) maybe you can make some sense of the wiring from the wire colors there.
1647351196063.png
 
Last edited:
Looking good @Engineer8000! I've had a dynamic last few months but looking forward to getting back on this project shortly. What do you think are the chances of you having a clone of the 24V amp (or one of your sample/demo amps) available soon?
 
jblueridge said:
My 4 cylinder diesel idles roughly, as in shakes the truck, so I increase the idle rpm with the hand throttle. When the ac kicks in the rpm's drop a bit so I adjust by hand again. Since my ac is currently controlled only by a dash switch, this manual method is no big deal.
Click to expand...
@jblueridge are you just manually switching the AC compressor clutch to the 10A supply that is supposed to be feeding the AC amp? How much do you have to manually cycle it on/off to keep the expansion valve or evaporator from freezing up?

and @Engineer8000 per your question about idle-up, it looks like in both my manual and the pic you've got that the signal to the clutch is also what triggers the idle up. I haven't gone searching to see if I have a VSV anywhere to accomplish this, but my guess is not.

Foolishly when I had the evap assembly out to rebuild it, I should have traced the harness to the thermistor and pressure switch 🙄.
 
Last edited:
Well I spent the afternoon tracing harnesses and I'm not yet sure what to think.

I have a button for A/C in my climate cluster, but no obvious 'volume control' similar to what @Engineer8000 demonstrated in the analysis video. It's a pain in the ass to get that cluster out further, but I think the temperature control slider is only mechanical if I remember correctly. I can try to dig into that further. The button has three leads coming from it, and I can't tell if it's supposed to be illuminated when the AC is on to justify that third lead.

The obvious-seeming place to plug the compressor clutch into is part of a much larger harness in the engine bay, and I haven't been able to trace that connector back to anything under the dash yet. There is another harness that goes to the engine bay from the AC stuff and currently they aren't connected to anything. One goes to the driver side and is a bit short to get to the clutch but it could, but strangely it's a 2 position harness and I don't know what the other position would be used for. The other harness end goes up near the +ve side of the 24V battery bank, and it's also currently just floating. There is a fuse in the dash labeled AC, so presumably the AC system should be pulling from that rather than some direct battery connection. The purpose of this is also pretty unclear. It is certainly possible that these two harnesses are swapped in orientation and supposed to be for a 2F instead of a 2H, and it's not certain to me that this whole AC harness isn't it's own island in the harness system - so far I haven't been able to find any power on it. I do see another random spot on the main engine bay harness that would connect to the AC harness if the orientation was swapped, so I guess I'll have to chase that down and see where it goes.

There are another three connectors in the area near the evaporator, and I just finally found one that is connected to the AC fuse.

I wonder would I find idle-up VSV functionality on a 2H?

Will continue tracing this nest tomorrow.

PXL_20220702_022914980_2.webp

PXL_20220702_023610879_2.webp



PXL_20220702_024039061_2.webp
 
Yes I just ran a power wire from a fuse tap to a toggle switch in the dash. I don’t know why a generic toggle was there when I bought the truck. I took the PO’s switch out and replaced it with a 20 amp model. Continued the wire from switch through firewall and down to the one wire ac clutch. I flipped it off every 15 or 20 minutes and let the fan begin to blow warm before repeating.
 
I don't think that dash control is set up for the "volume" control. It should have a slide pot like this connected to the temperature control. You can get around this by jumpering the volume pot input, fooling the amp that it is set on max.

ac control.webp
 
I remember that the wiring that goes into my ac amp is slightly different than what the manual shows. Some of the wire colors are different. Also, the single wire that goes to the clutch has cloth braided insulation. That might have been installed by the killer mechanic who installed a new compressor for me.

1656757220614.webp
 
Interesting. After considering overnight I think this is starting to make sense.

My dash is a bit a mix of a the standard 24V HJ60 vehicle harness, as well as some things from a donor FJ60. In hindsight my HJ60 likely did not have any of the evaporator assembly, and so when I moved that over from the FJ60 I likely moved the AC sub-harness which I think I can now see is an independent chunk (and connects up to connector 4 in your BJ/HJ 70 wiring diagram). I think I now understand where that comes from the stock harness. That would explain why the engine bay part of the AC harness is not correct for my engine layout - this is an FJ60 AC harness, not an HJ60 AC harness. That would also explain why the AC amp connector appears to be formatted for the FJ60 12V AC amp instead of the 24V AC amps that you've got samples of.

I was also under the impression that the temperature slider was only an actuator "cable" that went to the valve on the heater hose just inside the engine bay. If it also has a slide pot on it, how does the heater valve get bypassed when in AC mode? As I recall those rigid cable things make it a heck of a job to get that control panel in/out.
 
Engineer8000 said:
Ok. I have two 24v AC amplifiers on the shelf.
Click to expand...
I know this is lik3 4 years later, but have you one of these 24v amplifiers laying around?
 
You must log in or register to reply here.

Share this page

Back
Top Bottom