JZA80 Supra aircon issue

[nexx]

Hi guys, looking for a bit of help with my aircon...

First, some background.
I've put a 2JZ-GTE from a JZS147 Aristo in my JZA80 Supra and I've wired the car up with a ViPEC loom and made an adapter to the stock ecu, I then continuity tested everything to make sure it's all correct.
The engine ran and idled fine but has no balancer or water pump currently so for now I'm not running it. Some of the dash is also not in the car. The ECU is an Aristo item.

So herein lies the issue:

My climate control panel is all lit and appears to be working, the AC button turns on and off and I have ~11.94v at the Aircon magnetic clutch relay trigger (ACMG pin) when the ignition is on, also (worryingly though) when the aircon switch is on or off.

I've looked through wilbo's wiki and the wiring diagram here http://wilbo666.pbworks.com/f/JZA80%...505%203-50.png
It shows that the A/C magnetic clutch relay is low side driven (trigger pulled to ground) by the ACMG pin at the ECU.

I connected the ACMG trigger to battery ground up at the ecu side of the connector near the fusebox with a spare piece of wire, and sure enough, the relay triggers. Makes sense.
Now, when the AC is off, I get 0v at the AC request pin on the ecu, when the AC is on I get ~3v at the AC pin and at orange connector IJ1 pin 31.

The description of the AC pin from wilbo's wiki "This pin is connected to battery voltage to request that the AC be turned ON." makes me think I have an issue with a bad earth? maybe because the dash isn't fully connected? because I figure I need 12v at the AC request pin. I connected 12v to the AC request pin briefly but from the awkward position inside the car couldn't tell if the relay triggered and couldn't get a multimeter to the ACMG wire.

After talking to wilbo, he said that the MGC pin at the AC ecu (which runs to the AC request pin) pulls to ground when the AC is on. Which makes sense because a lot of people bypass this straight to the ACMG trigger.

Is this because the engine isn't running? and therefore the AC ecu sees no signal from either the tach or the compressor speed sensor and therefore refuses to output 12v on the AC request pin and then pull it to ground? that or a bad ground are all I can think of.

Sincere thanks for any help!

[Daddio]

Have you got the system gassed? The clutch wont get an engage signal unless the pressure switch senses pressure in the system. (Similarly if the system is over pressure, the clutch signal will be cut)
It may be worth temporarily bridging the high and low pressure switches to test?

[nexx]

It's gassed (didn't disconnect the compressor from the system when I switched from GE to GTE... BUT, the SSR and IG+ pins aren't connected (the connector is just sitting loose in the bay). Where's the pressure switch located?

[dumbass]

i can sort it out for some folding stuff
if u get stuck
think i saw this car out at capalaba way the other week

[nexx]

i can sort it out for some folding stuff
if u get stuck
think i saw this car out at capalaba way the other week

Haha nah mate, I wish! but 5 minutes down the road literally! Too many damn people were copying off my car before I had to pull it off the road and sell the wheels etc , they say imitation is the sincerest form of flattery; shame the other guy who's car is almost identical drives like a complete idiot! I'm thinking it's lack of tach, compressor or pressure switch signal that's causing the issue but I'll know by Saturday night! Might have to give you a call if it's still playing up no dramas at all, I'll make sure to look after you. Cheers!

[dumbass]

I've done about 20 2js into surpass so heaps around in Australia
Even an l98 into one

[Daddio]

Nexx...pressure switches are in the hard line on the chassis rail I think...low pressure switch and high pressure switch can be temporarily 'bridged' to test, but am not 100% sure on the RPM signal being needed.

[dumbass]

That's cool
I normally don't work on cars from forums because of certain things heheheh

[wilbo666]

The description of the AC pin from wilbo's wiki "This pin is connected to battery voltage to request that the AC be turned ON." makes me think I have an issue with a bad earth? maybe because the dash isn't fully connected? because I figure I need 12v at the AC request pin. I connected 12v to the AC request pin briefly but from the awkward position inside the car couldn't tell if the relay triggered and couldn't get a multimeter to the ACMG wire.

After talking to wilbo, he said that the MGC pin at the AC ecu (which runs to the AC request pin) pulls to ground when the AC is on. Which makes sense because a lot of people bypass this straight to the ACMG trigger.

Sorry, my wiki was incorrect. I'm sure that the JZA80 climate ECU connects it's AC demand pin to Ground, not Battery voltage to request the AC comes on. I've updated my wiki.

I'll need to check JZS147 however...I recall hearing people having issues when swapping JZS147 engine ECUs for JZA80 engine ECUs in regards to AC...?

Cheers
Wilbo

[nexx]

Sorry, my wiki was incorrect. I'm sure that the JZA80 climate ECU connects it's AC demand pin to Ground, not Battery voltage to request the AC comes on. I've updated my wiki.

I'll need to check JZS147 however...I recall hearing people having issues when swapping JZS147 engine ECUs for JZA80 engine ECUs in regards to AC...?

Cheers
Wilbo

I think you're right there, I've definitely read the same. The relay trigger still pulls to ground but I'm fairly sure the AC demand is 12v. Unfortunately I don't know anyone with a JZS147 or I'd check for you.
Going to put the motor back together tomorrow and I'll update then. Fairly safe at this point to assume that it's because it's not running and the AC ecu isn't happy to engage the clutch.