Jump to content
SAU Community

Recommended Posts

Hello everyone,

I want to thank you for any info in advance. I have searched the forum but need help finding the answer. I Have an R33 Gtst and swapped it to an RB25det NEO with NEO ECU. For the swap, I used a wringing specialties harness, and it has come together prefect only issue is the AC does not work now. I did keep all of the R33 AC components. I noticed that the R34 has a two-wire AC pressure switch, and the R33 has a four-AC wire pressure switch. Has anyone else done this or know the fix?

Link to comment
https://www.sau.com.au/forums/topic/484330-neo-swapped-r33-ac-help/
Share on other sites

  • 3 weeks later...

The R32 & R33 skylines have the refrig pressure switch in series with the power supply to pin9 on the Ecu. If you press the AC button the the Ecu earths this pin and the ac compressor switches on. If the refrig pressure is low it will open circuit this power supply to the Ecu and prevent the ac compressor from switching on and damaging the compressor. 
in the R34’s the refrigerant pressure switch is wired independently of the power supply to pin 14 (equivalent of pin 9 on R33) the controls the ac compressor operation. The refrigerant pressure switch provides a signal to the ecu at pin57 to tell it the refrigerant pressure is ok. Without a signal the ecu won’t Switch the ac compressor on. The plugnplay looms I have done in the past for this swap have included a small power feed to pin 57 to make the ecu think the refrigerant pressure is ok. I use the 5v power from pin48 through a couple of 2.2kohm resistors to drop the voltage to approx 2.6v.
The alternative to this is to install a switch in the cabin that simple earths the old pin9 to manually switch the ac compressor on. 

  • Thanks 1
23 minutes ago, BH_SLO32 said:

The R32 & R33 skylines have the refrig pressure switch in series with the power supply to pin9 on the Ecu. If you press the AC button the the Ecu earths this pin and the ac compressor switches on. If the refrig pressure is low it will open circuit this power supply to the Ecu and prevent the ac compressor from switching on and damaging the compressor. 
in the R34’s the refrigerant pressure switch is wired independently of the power supply to pin 14 (equivalent of pin 9 on R33) the controls the ac compressor operation. The refrigerant pressure switch provides a signal to the ecu at pin57 to tell it the refrigerant pressure is ok. Without a signal the ecu won’t Switch the ac compressor on. The plugnplay looms I have done in the past for this swap have included a small power feed to pin 57 to make the ecu think the refrigerant pressure is ok. I use the 5v power from pin48 through a couple of 2.2kohm resistors to drop the voltage to approx 2.6v.
The alternative to this is to install a switch in the cabin that simple earths the old pin9 to manually switch the ac compressor on. 

Thank you for this information, I greatly appreciate it. When you drop the voltage on pin 48 to 2.6v are you connecting it to pin 57 Or does the voltage just need to be dropped inline to send the signal to the ECU ? Thank you again for your help. 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Out of curiosity, how do you cover up the inspection hole? Surely it doesn't sit open like that, right? With grime and dirt coming in and oil going out?
    • Hi from Canada, Both of my calipers are starting to fail. My car is a 2005 M35 Stagea ARX and I can't seem to find any parts or any cross reference caliper that would fit my car. Is there a company or a similar caliper that would fit and I could replace the OEM one. Or if anyone knows where I can find a new OEM. Any help is very appreciated. Let me know!
    • Maf is a question mark but TPS  I have set at 0.47, the fact that I’m getting proper voltage range out of it with the key on leads me to believe it’s functioning properly. I’m getting proper voltages on basically everything. I still need to look up voltage ranges for z32 maf and test that 
    • Honestly no not at all, but it’s a very basic tune, it’s stock injectors q45 tps and z32 maf. Other than that it’s a completely stock base map. The file is from nistune and from my understanding if it was tune related I would be able to unplug maf and tps and it would still start even if it was a really shitty start. I have tried starting it with coolant temp, maf, and tps unplugged none of those 3 togethor or individually changes anything 
    • 🏆 Skyline Supremacy Meets Mount Panorama Magic 🏆 Join SAU NSW as we take the long way to Bathurst, the home of GTR greatness. Saturday 30th August 2025 7:00AM Meeting Hanna Park North Richmond 7:30AM Departure Cruise Via Bells of Line Road 9:00AM Arrival to Stop 1: Golden Poplars Meadow Flat 9:45AM Arrival to Final Destination: Mount Panorama Motor Racing Circuit Meet Location: Hanna Park North Richmond Stop 1: Golden Poplars Meadow Flat Final Destination: Mount Panorama Motor Racing Circuit   *Disclaimer* There will be a lead and follow car so no one should get lost. If you would like to attend or bring others along please put your name down and a +1 as numbers will be needed prior! This is NOT a race and we will all be adhering to all road rules. If this is what you want please come to one of our many track days. This is an official SAU:NSW event and will be run under a CAMS permit. One of the things that really sets our club apart is our commitment to being true enthusiasts. When on normal roads we strive to maintain good relations with the authorities as well as the public in general. When attending one of Skylines Australia NSW events please try to: • Be aware of surrounding environment and act accordingly. • Drive courteously on the state’s roads as a true enthusiast should. • Understand how important it is to maintain the good name of SAU NSW and thus, treat others accordingly. • Any misbehavior will not be tolerated and you will be asked to leave.
×
×
  • Create New...