Factory ECU - A/C pins do what?

[1JZ-Rolla]

Ok bit more research, from the Supra TSRM, it suggests "testing" the mag clutch function by bridging the A/C pin and E1 at the ECU and checking for 12v, which suggests that the original ECU expected to see a ground signal from the amplifier on that A/C pin yeah?

So are you saying that from your jap diagrams, the JZX100 VVTi ECU expects to see 12 volts instead?


Cheers
Phil

[dumbass]

cool
ive done heaps and never worry bout runnign it thru ecu
i run a relay
only problem some air con guys tell me is that some compressors dont like hi rpm
but ive never seen one explode due to hi rpm

[dumbass]

i think originally u would have had 12v on ac wire when its on
but maybe u need a ground going by the diags
but its easy to check
just ground the ac wire thru a 1k resitor

[1JZ-Rolla]

Yep, that makes sense, will check tomorrow.

Your bypass setup running without ECU intervention via a relay instead, would that mean the idle-up function doesn't work anymore either?

[dumbass]

I think if u get the ac wire correct input it will idle up

[The Witzl]

If u bypass with the relay like dumass suggests, I think u will lose functionality such as the ecu cutting the compressor off when you flatten the throttle, or if rpm drops too low, etc.

[dumbass]

sometimes u have to fit a relay because if this was a customers car
he would have to charge him 1000 bucks extra for the air con
because he has spent 2 days to get it to work properly,
no one these days wants to pay a shop to figure things out

[1JZ-Rolla]

Didn't get enough time for a thorough test today, but did get under the car to pull the 3 pin plug on the aircon compressor. Tried to trigger the magnetic clutch by bridging the wire to 12V, but no response, possibly because I used a test light and therefore it couldn't pull enough current?

Also hooked up the test light to the wire from the ECU (or Mag clutch relay rather) while switching the aircon on and off at the dash. When switching ON, test light illuminates only for a moment, then nothing till you cycle it back on and off again. Perhaps an issue with the compressor RPM signal?

[dumbass]

If the old ac had compressor rpm signal then u need to hook it back up
If its hard u might need to trick ac amplifier
Without looking at setup it's hard to say

Also don't worry bout the mag clutch wire for now
If u have wrong signals or no signal in to ecu
U won't get a signal out
So u have to concentrate on the ac signal in terminal
Or othe ac2 and the other one

[1JZ-Rolla]

Its still the same compressor as before, I switched it to the new motor. New loom has this connected from the engine loom to the body loom plugs. Might need to check for continuity to the AC Amplifier, if I can find a pinout diagram that says which pin is which.

Will sort out the ECU trigger side of things first, especially since the idle up business is backwards. Hopefully have time while there's enough light outside tomorrow. THanks

[1JZ-Rolla]

Ok, so had a chance to test the wiring between the A/C amplifier and ECU today


From the original car (JZA70) A/C Amplifier loom to ECU:

A/C OFF - 0 volts (but open circuit, not grounded)
A/C ON - 12 volts output to ECU AC1 pin


From the JZX100 VVTi ECU to the Mag Clutch relay (ACMG pin)

A/C OFF - 0 volts (open circuit, not grounded)
A/C ON - 12 volts


AC2 pin has nothing connected at the ECU, since the car's A/C amplifier doesn't have an output for this



A russian diagram I found for the VVTi 1JZ suggests that the voltage from the A/C amplifier should be the reverse of the above, which could explain the idle-up being backwards. But the rest of it I can't get my head around...........

[EDIT]One more thing, the car's mag clutch relay must be triggered by Ground, not 12V, because when I backprobe the ACMG pin on the ecu with a test-light connected to the chassis, the compressor starts.


Cheers
Phil

[dumbass]

well cut the acmg wire that goes to the ac mag clutch relay
ground it or give it 12v and see which one makes clutch click in
i could solve your problem but yr too far away heheheh
is one of those problems which takes ages and sometimes simple thinking

[1JZ-Rolla]

Edited above dumbass, thanks for the quick response. Had the same thought as you were typing that I guess, and did exactly that. mag relay is triggered by GND not 12V. How to interpret that for the AC1 wiring i'm not sure.........

appreciate your assistance, and that normally someone would have to fill your pocket with cash for something like this in a workshop

Cheers
Phil

[dumbass]

what i do is measure the wire when its not cnnected to anything
like the acmg wire so since its an output
if u measure it not connected to ecu u get 12vs when air con switch is on
this is caue u measre 12v thru relay so if u ground it then it turns on

so with the ac1 wire dont connect it to anyhting but the ecu end since its an input
measure wire and most cases what ever u measure u need to put the opposite
and when testing always use a resistor to make sure u dont hard ground it and stuff things

basically start at acmg and work your way backwards
and sometimes u need to trick things
its all trial and error and takes years of wiring to learn only half the stuff thats out there heheheh

[1JZ-Rolla]

That makes sense thanks.

Would a test light be enough resistance (10ohms) for what you describe above (so as to not hard ground it)?