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NEO Swapped R33 AC Help

2TON

By 2TON,
in R Series (R30, R31, R32, R33, R34)

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2TON Rookie

2TON

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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?

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  • 3 weeks later...
BH_SLO32 Proficient

BH_SLO32

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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. 

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2TON Rookie

2TON

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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. 

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