I Want My A/c!
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S14DriftinThruFL
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- Joined: Wed Jun 25, 2003 7:45 am
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I Want My A/c!
ok, so i called up mckinney motorsports in regards to their custom wiring harness they could build me to swap the rb20 into my 97 s14. only thing is, he said my a/c wouldnt work, because the 95-98 240sx use a completely different a/c unit than any other nissan out there. but living in florida results in some very hot and humid days, where going with out a/c sucks. Someone please drop a line whether they kept their a/c or not, and if so, how they did it. thanx
I believe the A/C can work, although I have not yet proven it. When I do, I will let you know (on an 1995 S14).
All of the A/C systems work pretty much the same. There is a thermo control amp that turns on and off the A/C compressor to control evaporator temperature. The thermo control amp needs to send a signal to the ECU to turn on the A/C. The ECU then decides whether or not to turn on the A/C based on engine speed/load by sending a signal to the compressor clutch or the compressor clutch relay. In addition, there is an FICD solenoid that needs to open when the A/C clutch engages.
I have looked at the RB25, KA24E, and KA24DE wiring diagrams, and all are very similar in this regard. Should be a matter of 2 or maybe 3 wires. One from the thermo control amp to the ECU, one from the ECU to the clutch or clutch relay, and maybe one from the ECU to the FICD.
Like I said, I do not believe wiring the A/C has to be magic, but I have no proof as of yet.
Mounting the S14 compressor on the RB could possibly present a fabrication problem... I do not know if it is a direct fit. The S14 is a good compressor, tho, so I will be trying to keep it.
Shane
All of the A/C systems work pretty much the same. There is a thermo control amp that turns on and off the A/C compressor to control evaporator temperature. The thermo control amp needs to send a signal to the ECU to turn on the A/C. The ECU then decides whether or not to turn on the A/C based on engine speed/load by sending a signal to the compressor clutch or the compressor clutch relay. In addition, there is an FICD solenoid that needs to open when the A/C clutch engages.
I have looked at the RB25, KA24E, and KA24DE wiring diagrams, and all are very similar in this regard. Should be a matter of 2 or maybe 3 wires. One from the thermo control amp to the ECU, one from the ECU to the clutch or clutch relay, and maybe one from the ECU to the FICD.
Like I said, I do not believe wiring the A/C has to be magic, but I have no proof as of yet.
Mounting the S14 compressor on the RB could possibly present a fabrication problem... I do not know if it is a direct fit. The S14 is a good compressor, tho, so I will be trying to keep it.
Shane
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S14DriftinThruFL
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- Car: tuning imports
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FAST-DATSUN
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To clarify the AC problem the SR/RB computers control the AC system differently. You can piggy back the stock computer to control the AC or build something to control the system OR cycle the system your self, but most shop will not take the responsible of setting this system up as it could lead to failure if the customer does not cycle the system. Some shop out there mayhave a partial system working, but I know of no one with a full system with out using the KA computer to control the AC...
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S14DriftinThruFL
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- Car: tuning imports
i have a 97 240sx S14. if i were to do a sr20det blacktop s14 full clip swap, AND purchase the actual silvia a/c controller and all or whatever its technically called, (you know the digital a/c thermostat that you can buy off ebay) would my a/c work then? in otherwords, just make the WHOLE damn car a true 97 s14 silvia? sorry that took me so many words to get out. thanx
Cycle the system? That is not done by the ECU at all. The thermo control amp cycles the system by turning off and on depending on the evaporator temperature. That is true for the RB20 and both the S13 and S14 as far as I can tell. The role of the ECU is to cut the A/C if the driver is demanding high load or if the engine is too hot.
So here's what I can tell. You need to do 3 things:
1. Connect S14 F3 pin 46 to pin 46 on the RB ECU. This sends the thermo control amp signal to the RB ECU.
2. Connect S14 F3 pin 43 to pin 9 on the RB ECU. This lets the ECU turn on the compressor relay.
3. Connect the powered side of the RB FICD to the S14 A/C compressor relay. The Skylines power the FICD thru a relay, but the S14 has it just connected in parallel with the compressor clutch. This connection could probably just be made directly to the relay in the engine bay.
Those pin #'s should be verified since the S14 FSM is riddled with errors, but this is gist of what I believe needs to be done. The triple pressure switch is already integrated into the engine room harness, so no need to worry about burning up the compressor if you make a mistake. The compressor will still shut off if something is drastically wrong.
The RB ECU may also want a signal from an ambient temperature switch. I still need to find out what this switch does, but I think it just shuts off the A/C if the outside temperature is too cold. The S14 has this switch, so that should be no problem if the RB needs it. The S13 does not have it, fwiw.
The S14 ECU also controls the cooling fans based on part of the signal from the triple pressure switch; however, since electric fans are needed anyway, this should not be an issue.
These are the mods I plan to make if I can get the S14 compressor to bolt up. Anyone know if it does?
Shane
So here's what I can tell. You need to do 3 things:
1. Connect S14 F3 pin 46 to pin 46 on the RB ECU. This sends the thermo control amp signal to the RB ECU.
2. Connect S14 F3 pin 43 to pin 9 on the RB ECU. This lets the ECU turn on the compressor relay.
3. Connect the powered side of the RB FICD to the S14 A/C compressor relay. The Skylines power the FICD thru a relay, but the S14 has it just connected in parallel with the compressor clutch. This connection could probably just be made directly to the relay in the engine bay.
Those pin #'s should be verified since the S14 FSM is riddled with errors, but this is gist of what I believe needs to be done. The triple pressure switch is already integrated into the engine room harness, so no need to worry about burning up the compressor if you make a mistake. The compressor will still shut off if something is drastically wrong.
The RB ECU may also want a signal from an ambient temperature switch. I still need to find out what this switch does, but I think it just shuts off the A/C if the outside temperature is too cold. The S14 has this switch, so that should be no problem if the RB needs it. The S13 does not have it, fwiw.
The S14 ECU also controls the cooling fans based on part of the signal from the triple pressure switch; however, since electric fans are needed anyway, this should not be an issue.
These are the mods I plan to make if I can get the S14 compressor to bolt up. Anyone know if it does?
Shane
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FAST-DATSUN
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Re: I Want My A/c!
S14DriftinThruFL wrote: only thing is, he said my a/c wouldnt work, because the 95-98 240sx use a completely different a/c unit than any other nissan out there.
so, having said that--can they wire up AC on s13? hmm....
The S13 is even easier than the S14. Very simple, since the ECU is not controlling everything. But same scenario. One wire from the thermo control amp to the ECU, and one wire from the ECU to the A/C relay. On the S13, the fan is controlled by its own thermo switch (at the radiator) without going thru the ECU.
Shane
Shane
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Yellow4g63
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95 Nissan 240SX Stock - Contact: