Factory ECU - A/C pins do what?

[1JZ-Rolla]

By george I think we've got it!

ECU AC1 pin is 12v with nothing connected. bridge it to GND and the engine idles up, and the compressor switches on, just as prescribed


Just need to use a relay now to convert the 12v output from the A/C amplifier to GND instead, and baby jesus will be happy LOL


THanks mate for the pointers, much appreciated.

[dumbass]

cool
when diagnosing its best to work backwards as its easier to understand
good your getting there

[masterofsinanju]

Nothing to do with air con, but I think I spotted your Supra last week on Canberra Ave. I was in a bus a got a good view. It's a nice looking bit of kit.

Thanks to both of you for the aircon electrics debugging, tucked away for future reference.

[1JZ-Rolla]

Sounds about right Master, I'd be heading that way to/from work.
Cheers
Phil

[Z2TT]

You might find that the A/C Amplifier is not able to supply enough current through the wire to trigger a relay. In this case you need to use this wire to trigger a transistor to forward another 12v source to your relay.

The 2 wires from the A/C Speed sensor off the compressor goto the Grey Square plug on the jza70 near the fusebox, from this plug you can wire them into the appropriate wires into the vvti engines plug, or 2 wires that you know are unused. Trace those wires to the under dash plugs and then wire them into the wires that goto your jza70 a/c amp for the speed sensor for the compressor.

[1JZ-Rolla]

Um......... isn't the point of a relay to be able to switch a larger current from a much smaller current? anyways, will know soon Thanks for the pointer.

[dumbass]

can be used to change polarity also

[1JZ-Rolla]

Yep, in this case will only use a 4 pin micro relay wired like this:

pin 30 - GND
pin 87 - ECU AC1 pin
pin 85 - AC Amplifier output (12V)
pin 86 - GND

[1JZ-Rolla]

It works! woohoo!

Thanks for your help guys.

[dumbass]

so the other terminals didn't matter

just the acmg and the ac1?

[1JZ-Rolla]

Only the AC1 pin signal had to be changed from 12v ON to GND ON. Strange that toyota changed their logic in only a matter of a few years hey, but I guess they are known for mechanical interchangeability, while their wiring is completely nonsensical from model to model in many cases

ACMG remains unchanged - it now ouputs a ground to the mag clutch relay as it should.

Perhaps the internal circuitry in the ECU simply completes the circuit between AC1 and ACMG when conditions are within parameters?

[dumbass]

it could also be the ecu manufacturer changed
i still have issues tryign to understand what the small symbol means under the terminal label on the ecu diagrams
in the diags where u have the long ecu square with the terminals around it inside the ecu square under the terminals there
is symbols where they r pulled to ground and pulled to 12vs thru resistors and also 5vs thru resistors
once u work that out u understand what signal it means
i use a special test light that tells me voltage at the wires and i can put differnet voltages at the wire quickly
for testing so what takes people hours or weeks to go thru things takes me few hours or even less

[midnight_purple_GA70]

glad this thread came up now... can see it being of use to me soon enough