AC amplifier not working (1 Viewer)

[Dazed]

For my Isuzu diesel swap, I replaced the original FJ60 AC amplifier with one from an FJ62, as the diesel doesnt have/need a tach sensor and the 62 amplifier doesnt need one to operate. With the system all connected, the clutch is still not engaging. On further diagnosis I have found:

Things that make sense:
- signal from AC switch at pin 2 is good at 12V.
- signal from pressure switch at pin 3 is good at 12V
- pins 5 and 6 are confirmed connected to ground (I actually removed pin 5 for my application, but that will not affect anything here)
- thermistor is measuring about 1.2k or 1.3k (I cant remember which) when the vehicle is off. measured between pin8/9 and 6 of the connector to the amplifier
- wire from pin 7 to compressor is a short circuit (aka is connected and true)
- ignition signal is at 12V
- I can force the relay to switch - relay works

Things that don't make sense:
- pin 7 to compressor clutch is at 0V.
- Voltage on the base of the transistor that is acting as a switch for the relay is at 0V. This NPN transistor needs a "high" voltage to turn "on" and then connect its collector and emitter together to cause the relay to switch
- Voltage at output of Toshiba pins 4 and 6 is 0.15V.

Things to note but I do not know if they are correct or not:
- The voltage at the Toshiba pin3 side of the 110k resistor at connector pin 9 is 0V. This seems like it should not be, but I dont know why I think that.
- Voltage at the Toshiba side of the 1.1k resistor near connector pin 8 is at 2.02V.
- Other side of 300 ohm resistor in series with connector pin 2 is 5.86V
- Voltage at Toshiba pin 1 is 2.96V

Questions that I have:
- Issue is either the opamp or the thermistor (but I could reasonable be convinced otherwise too).
- Why would the opamp not be outputting a high voltage from its pins 4 and 6?
- Has anyone ever had an issue with the Toshiba opamp going bad? The Toshiba part looks to be an ASIC and there are no datasheets on it. I might be able to find one at the junkyard.
- Could the thermistor be the issue?

Does anyone have any thoughts about what could be going wrong? I could put a jumper between pins 2 (AC switch) and 7 (compressor clutch) but I would rather not, as I dont want to freeze my evaporator.

On a side note, I think that the opamp is actually a dual or triple comparator.

thanks for the help!
Dazed

 

[langsen]

Maybe you have this hooked up right already, but just to be sure, the ignition signal at pin A should be +12 volts only while the starter is engaged and not while the vehicle is running.

EDIT: I'm not 100% sure of this actually. On the HJ60 AC amplifier there is a connection to the starter that disengages the AC clutch while cranking. Not sure if it is the same on the FJ62 amplifier.

 

[bj40green]

The Toshiba T2333 is a DUAL COMPARATOR IC. This means that when all conditions are valid the outputs 4 and/or 6 are high or low and activate the transistor and thus the relay.
There are many reasons why it doesn't work, so I edited your diagram with the basic voltages.

It can be as easy as the transistor is defective or one of the 8K2 resistors is open or has a bad solder connection.
Other possibility is a bad capacitor with a short to ground.
Can you post close up pictures from component and circuit side?

Rudi

 

[Dazed]

Maybe you have this hooked up right already, but just to be sure, the ignition signal at pin A should be +12 volts only while the starter is engaged and not while the vehicle is running.

EDIT: I'm not 100% sure of this actually. On the HJ60 AC amplifier there is a connection to the starter that disengages the AC clutch while cranking. Not sure if it is the same on the FJ62 amplifier.

This looks to be the issue. I pull the connector after the truck was started and the AC clutch engaged. I also checked the wiring diagram for an FJ62 and it confirmed this. Thanks for the help! Now I need to figure out where to get the signal from: either the column or at the starter...

 

[FJ60Cam]

I just talked to Tom about this, as I used a 62 amp with my V8 swap since I couldn't get the ECU tach signal to trigger the 60 amp.

As langsen mentioned, the +12v to the spade terminal should not be constant. It should only see it while starting (starter solenoid).This interrupts the clutch while starting to reduce drag. So if it is connected all the time, it will never engage.

That connection is not required for AC operation, only for the starting interruption. (I believe this connection is actually in the 60 harness, but I haven't verified it yet.) Try disconnecting it and see if that fixes it.

 

[bj40green]

Here is my theory.
Part 1.
Pin 3 get's 6V from the 8K2 / 8K2 divider. This is a reference voltage. That same 6V goes to connector pin 9 and comes back at pin 8 which goes to pin 2 and 7. Now 3=H and 2=H so pin 4=H. If 2=L then 4=L.

Part 2.
Pin 8=H when key is in start position. When pin 7=H then 6=L preventing the A/C to run when cranking the engine.
Once pin 7=L then pin 6=H and allows the A/C to run.

I can't find the datasheet for this IC but I think that the top is an AND gate and the bottom a NOR gate. Just speculating from your schematic.

Rudi

 

[Dazed]

The Toshiba T2333 is a DUAL COMPARATOR IC. This means that when all conditions are valid the outputs 4 and/or 6 are high or low and activate the transistor and thus the relay.
There are many reasons why it doesn't work, so I edited your diagram with the basic voltages.
View attachment 1056319

It can be as easy as the transistor is defective or one of the 8K2 resistors is open or has a bad solder connection.
Other possibility is a bad capacitor with a short to ground.
Can you post close up pictures from component and circuit side?

Rudi

A note on your voltages after the AC switch 300 ohm in line resistor that goes into Toshiba pin 9. I do not think that they are correct due to the potential divider (300 ohm with 56k||6.2k, which has a gain of just less than 1) created by the line coming from connector pin 8, as that line on the other side of the 56k||6.2k is not at ground and has additional resistance. I am being too lazy to actually go do the maths on it though, especially as I measured it at 5.86V. The notes that you have as 6V will indeed be half of the voltage on Toshiba pin 9, but I would expect it to be about 3V as Toshiba pin 9 is at about 6V. I did measure Toshiba pin 1 to be 2.96V.

 

[Dazed]

Would there be any issues to the compressor clutch if I let it be engaged during engine start? Or would the only drawback be that there is extra strain on the starter?

 

[FJ60Cam]

This looks to be the issue. I pull the connector after the truck was started and the AC clutch engaged. I also checked the wiring diagram for an FJ62 and it confirmed this. Thanks for the help! Now I need to figure out where to get the signal from: either the column or at the starter...

Check out this wire for the +12 while starting. It is the same plug, same color, and same location on both the 60 & 62 harnesses.

62 harness...

 

[FJ60Cam]

Would there be any issues to the compressor clutch if I let it be engaged during engine start? Or would the only drawback be that there is extra strain on the starter?

It's just extra strain. You can always turn off the fan or push the blue button while starting. But I have a hunch the signal is right there waiting to be plugged in.

 

[Dazed]

I will go look for that plug. Part of the confusion for me is that the wire to the compressor clutch is also black-white but it much thinner. I am also colorblind and have gotten the Black-white and black-light blue wires confused in the past. Off to go check!

 

[Dazed]

Check out this wire for the +12 while starting. It is the same plug, same color, and same location on both the 60 & 62 harnesses.

View attachment 1056489

Well that was a a quick find. I undid that connector and then attached the appropriate end to the AC amplifier and it worked. I wonder if the other end is still connected to START or is it floating now. Either way, I am going to try to wrap it in tape so that nothing inadvertently contacts it.

Thanks for the help everyone!!!!

 

[FJ60Cam]

Did you test for 12v while starting? Or could you tell that the clutch was not engaged while starting?

The harnesses look identical, and the plug opening on the 62 amp cover is even shaped for that, so I figured it must be the same wire.

 

[FJ60Cam]

Not sure if I should spill the beans or not, but Tom (@TrickyT) has my 60 amp and is mapping it out like he did in the drawing above. We were curious if the tach signal/rpm requirements (blue knob) could be easily bypassed to function like the 62 amp.

Also, the 60 has an adjustable thermister cut-out (red knob), so in theory you might get the air degree or two colder without freezing the evaporator. I'm getting slightly higher temps than I did before.

If successful, this will be a huge benefit to the cruiser community since more and more people
are swapping motors and want working AC. (No pressure Tom!)

 

[TrickyT]

The A/C amp from the FJ60 uses a different integrated circuit than the FJ60. It's a Nippon Denso SE012 and I haven't been able to find a datasheet that describes it. As with the FJ62, it's likely a dual comparator because it needs to sense the input voltage across the thermistor relative to a reference voltage to decide when to shut down the compressor to prevent the system from freezing. This same IC is also used to sense engine RPM. It should be possible to disable the RPM sense circuitry and then use the FJ60 amp after a motor swap. The only downside would be that the compressor clutch doesn't get disengaged when the engine is being started, but you could handle that manually by switching off the A/C during startup. I'm in the process of tracing out the FJ60 amp circuitry, but lack of knowledge of details of the SE012 IC makes for some challenges when it comes to deciding how to disable the RPM circuit. (Sure hope I don't burn up Cam's amp in the process! )

 

[FJ60Cam]

...(Sure hope I don't burn up Cam's amp in the process! )

I hope that is nervous laughter and not evil laughter

Just kidding. I have cold air now, so no worries.

I just went and checked mine, and I am NOT getting the +12 while starting at either side of this connector. I don't see getting the motivation anytime soon to run the wire from the starter (or find one in the truck), so I manually disable it with the blue button. Or not. I forget half the time and the engine doesn't seem to care.

 

[Dazed]

I hope that is nervous laughter and not evil laughter

Just kidding. I have cold air now, so no worries.

I just went and checked mine, and I am NOT getting the +12 while starting at either side of this connector. I don't see getting the motivation anytime soon to run the wire from the starter (or find one in the truck), so I manually disable it with the blue button. Or not. I forget half the time and the engine doesn't seem to care.

View attachment 1056624

Cam
you're right. I just checked mine and didnt get +12V either. I also do not see myself having the motivation either. I have a gigantic starter for the diesel that I am sure can handle the AC clutch.

 

[GarethsSixty]

if your determined to use the toyota amplifier thats fine, Mine was screwed up, so i just bought one of these from china, set the switch off @2C and on @ 3degC, wired a relay into the clutch line to cut the circuit whilst cranking and it works great, with the benfit of displaying the evap temps.

was like $5aud. The thermister has a differnent temp vs resistance curve so i used the thermistor provided

 

[Dazed]

if your determined to use the toyota amplifier thats fine, .......

what is the link to buying this, do you know? A friend may be interested for another application.

 

[GarethsSixty]

http://www.ebay.com.au/itm/Temperat...45?pt=LH_DefaultDomain_15&hash=item58b6f1fdf1

i purchased a few so i can utilise them for an intercooler and condenser fan, they seem to work quite well