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Old 08-05-2016, 06:39 PM   #1
dbeiler
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AC system install in RB25 swapped '96 S14

Here's a little DIY write-up on the AC system I recently installed on my S14.

Not having AC sucked. I hated driving my car in the rain because it was difficult/impossible to keep the windows defogged. I was forced to drive with the windows cracked open which allowed rain water to streak onto the door panels. Driving in hot weather was equally unbearable.

The car: '96 240sx SE with a build date of 10/95
The engine: '95 S1 RB25DET

Parts used and cost:
$123. AC line extension by custom AC shop
$60. '94 Infiniti J30 salvage yard AC compressor
$18. AC compressor belt Dayco 5040358
$9. AC refrigerant oil
$60-$100 AC system refrigerant charge

This may not work for every S14. Apparently Nissan did some screwing around with the AC system components through the years of the S14. The firewall connectors changed after S14 build date 10/95. My '96 was build date 10/95 which means it falls into the early Zenki range. Most Zenkis will use the same AC lines I used during the install. Post 10/95 Zenkis and all Koukis will use different lines.

Here's another oddity. The low side line on my 10/95 S14 was slightly different from my old 11/94 S14. The firewall and compressor fittings were identical but the line OD was bigger in the 11/94. The low side line is divided into 3 pieces on both models. I could not mix and match the pieces because the 11/94 used a bigger line ID and connector fitting sizes.

The RB25 AC compressor is not designed like the S14 compressor. The S14 uses a compressor that utilizes a swashplate to vary the displacement according to demands. This means the compressor clutch can always remained engaged and the cabin vent temperatures will remain constant and stable regardless of engine rpm. I haven't yet disassembled the RB compressor to see what's inside. It's a rather small compressor so it's safe to assume it doesn't have a swashplate or variable displacement. The J30 is a mirror image of the S14 compressor with the exception of the mounting holes. Fortunately, these mounting holes can fit the RB compressor bracket with minimal modification.

The J30 parts. This is what the J30 AC system looks like. The high line and drier are routed on the driver's side.


Compressor fittings. Terrible pic, I know.


Both high and low lines are routed along the firewall to the driver's side.


I removed a bunch of parts to access the compressor.


Access granted




This is the J30 AC system layout. Both high and low lines are routed to the driver's side. The only part I used on my S14 was the AC compressor.


The S14 AC system layout.


Compressor bracket comparison. S14, J30, and RB25. I used the J30 idler pulley because the RB bracket was missing it. Fortunately, it fits perfectly.


S14 vs RB bracket.




Compressor comparison: S14, J30, and RB25




S14 vs J30




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Old 08-05-2016, 06:52 PM   #2
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RB25 compressor on RB25 bracket


J30 compressor mounted. See how the pulleys don't line up correctly? That must be fixed.


I used two washers as spacers on each upper mounting bolt


Spacers installed


Now, of course, the lower bolt holes don't line up.


I used a Dremel with a cutting bit


Elongated the holes till the bolts would fit in correctly.
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Old 08-05-2016, 07:04 PM   #3
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This is awesome! Thanks so much for the information. Haven't seen many good write-ups like this for at least 5 years. Out of curiosity, how much lighter is the J30/RB25 compressor bracket that the S14 bracket? Maybe I am blind, but it appears the RB/J30 bracket is made of Aluminum? I would think this would be immensely lighter. Thanks!
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Old 08-05-2016, 07:27 PM   #4
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I added some refrigerant oil to the compressor, evaporator, condenser, and dryer.


I attempted to use the J30 low line. It didn't work. The compressor connection is directly in the way of the turbo intake snorkel. It's too short to reach from the firewall to the compressor. I tried to straighten out the bends to make the line reach further but ended up cracking the line. I also broke my throttle cable firewall grommet/bracket in the process. The J30 low line isn't worth wasting time on. The S14 low line is 9" too short. Must be lengthened to work.

S14 low line installed. I had to bend it slightly downward to clear the power steering pump. The pump adjustment bolt needed to be trimmed down 1" to clear the line.


9" too short




AC shop removed old rubber hose section and replaced with new longer hose.


Installed. See how the power steering pump adjustment bolt interfers with the line? I cut the bolt down 1".


The remaining AC system is all original S14 equipment with the exception of the condenser. It is a Rockauto replacement unit. The condenser is located in the original condenser brackets and a set of Flex-a-lite 432 pusher fans are mounted in front. The fan controller has a trigger wire routed to the AC compressor clutch power wire. The fans are on whenever the compressor clutch is on. I'm using a Wiring Specialties engine harness. It comes with the chassis plug correctly wired for AC. I spliced the AC compressor connector to the S14 harness. The J30 and S14 use a different connector.

Condenser mounted


FAL fans mounted
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Old 08-05-2016, 07:47 PM   #5
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The end result. All lines installed.


High line fits perfectly




Surprisingly, the drier and bracket clears the Q45 throttle body and RAW radiator hoses without too much trouble.


Low line installed






Hooked up to the AC service cart. System was drawn down to vacuum then charged to capacity with 1.5lbs of R134
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Old 08-06-2016, 04:50 AM   #6
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Nice write up. Clean car!
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Old 08-06-2016, 08:08 AM   #7
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Very good write up. Thank you for going through the trouble of making it. I do have two question for you though. Are the FAL fans enough to keep your car from overheating while running the a/c? What's the highest daytime temperature you've had it out in. I gets 100degF + where I'm at, and with your setup giving some of the most engine clearance, it gets the wheels turning in my head. Thanks.
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Old 08-06-2016, 09:49 AM   #8
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I love the detail of this.
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Old 08-06-2016, 07:08 PM   #9
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Quote:
Originally Posted by claaasssiiiccc21 View Post
This is awesome! Thanks so much for the information. Haven't seen many good write-ups like this for at least 5 years. Out of curiosity, how much lighter is the J30/RB25 compressor bracket that the S14 bracket? Maybe I am blind, but it appears the RB/J30 bracket is made of Aluminum? I would think this would be immensely lighter. Thanks!
Yes, the J30 and RB brackets are aluminum. That's an interesting thought. I'll throw them on the scales one of these days.

Quote:
Originally Posted by Rb26kouki View Post
Nice write up. Clean car!
Thanks!

Quote:
Originally Posted by UniqueAutoCreations View Post
Very good write up. Thank you for going through the trouble of making it. I do have two question for you though. Are the FAL fans enough to keep your car from overheating while running the a/c? What's the highest daytime temperature you've had it out in. I gets 100degF + where I'm at, and with your setup giving some of the most engine clearance, it gets the wheels turning in my head. Thanks.
The FAL fans kick ass. I'll never use anything else. I'm using a 68C engine thermostat. The temperatures usually hover around 70C. I've never seen anything above 75C no matter how hard I street thrash it. Hopefully I'll have the same result on the track. Daytime temperatures go up to 80-90F here but we have high humidity.

Quote:
Originally Posted by Sileighty_85 View Post
I love the detail of this.
I've found tons of useful information on this site, and especially your threads. I'm attempting to return the favor.
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Old 05-08-2018, 01:51 PM   #10
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Sorry for reviving a two-year-old post, but hopefully you are still around to answer a question dbeiler.

I'm in the process of installing ac in my 96 s14 now, mostly the same setup as you but rb20det with the j30 compressor. My question is about the wiring. The s14 ac wiring is running the j30 compressor without problems?

I thought something had to be changed in the wiring for the s14 to control the j30 compressor correctly, but I am still trying to figure this out. I honestly know very little about wiring and next to nothing about AC stuff.
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Old 05-08-2018, 08:51 PM   #11
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There is only one wire to the AC compressor. It is the power wire for the compressor clutch coil. I simply cut the old connector off my S14 harness and spliced in the new J30 connector pigtail. Since I'm using an E-fan setup with a fan controller, I spliced a fan trigger wire into the compressor clutch coil wire. Whenever the clutch engages, the E-fans come on.

As far as the chassis wiring goes, I can't offer any assistance. I have a Wiring Specialties harness which comes with all the chassis (M63/F3) to ECU wiring completed. I attempted to figure out how it was done, with some continuity checks, but quickly realized I would need to deloom and disassemble the wire harness. I don't want to do that just yet.
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Old 05-09-2018, 10:39 AM   #12
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Ok, makes sense thanks.

I found a post today describing the changes to the wiring if anyone should be curious: http://forums.nicoclub.com/topic267002.html
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Old 05-22-2019, 10:54 PM   #13
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How is everyone wiring up the pressure sensor from the J30 ac system. The RB has two wires but the J30 has 1? I have an R32 And in the middle of this now but can’t find any info on how to integrate the new pressure sensor with the chassis.
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Old 11-30-2022, 11:51 AM   #14
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Quote:
Originally Posted by dbeiler View Post
There is only one wire to the AC compressor. It is the power wire for the compressor clutch coil. I simply cut the old connector off my S14 harness and spliced in the new J30 connector pigtail. Since I'm using an E-fan setup with a fan controller, I spliced a fan trigger wire into the compressor clutch coil wire. Whenever the clutch engages, the E-fans come on.

As far as the chassis wiring goes, I can't offer any assistance. I have a Wiring Specialties harness which comes with all the chassis (M63/F3) to ECU wiring completed. I attempted to figure out how it was done, with some continuity checks, but quickly realized I would need to deloom and disassemble the wire harness. I don't want to do that just yet.
How can we contact you?
Had a couple questions
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