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R32 vs R33 R34 C34 heater core matrix and elbow pipes info thread


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·        S13 240SX & Z32 300zx 90-94 cores and elbows work on R32’s.  

·        93-97 Altima cores and elbows work on R33 and R34 (and C34 Stagea, Laurel, etc). 

·        Flip the elbows around 180 degrees for both to work on RHD cars. 


Through some voluntary and involuntary R&D, I recently just performed this job on my R32, so I am passing some of the learnings on to the community, since part selection isn’t very well documented, and partially out of date as I found out.  Thankfully, some generic aftermarket parts will work from other vehicles, which will help reduce the overall cost of this job.


Good verbal how-to for removing the core without removing the dash, which isn't terrible once the AC and coolant systems are drained:


Note: see my comments about the Conceptua Concepts core’s design in an R32 at the bottom.


General Heater-Core System Notes:

        Nissan likely revised their HVAC system for MY93 (Model-Year 93), so many compact Nissan vehicles launched after that used this new elbow design (until 2001-ish); IE: MY93 R33’s and through R34’s. 

        I am not sure how widely used the core/elbow designs were spread, but it’s a good cost-saving measure, but it seems Nissan did a decent job of parts sharing for the core/complex components of these sub-systems to cut costs through increased volume (amortization)…  With exception for the evaporator core, which will have to be another project for someone else.  Thankfully Nissan still sells the R32 evap core, but it’s very expensive.

        Following other threads about common USDM air-conditioning parts working in R32-4 cars, like 240SX (exp valve) and 300ZX (dryer), I dug deeper into this for heater cores. 

        R32 Firewall heater core seals: 92580-01E00

        R32 Firewall evap core seals: 92560-71L00


General Elbow pipe notes:

        Fundamentally, on the R32 vehicles, there are 2 different elbow designs: 1 is valved to allow coolant to flow or not flow into the core depending on HVAC temp setting – it’s tied to the blend door.  The other/lower elbow is a regular bend.


        In MY93 (R33 & R34) I believe they eliminated the valved elbow, which may explain why none of the aftermarket includes these anymore.


        Nissan does not make the valved upper elbow anymore, and/or guards the patent for it so that the aftermarket cannot either.  This is likely due to cut costs, and perhaps that the Max-AC performance wasn’t reduced significantly, or the MY93 HVAC redesign may have changed the blend door open ratio programing.

        Using a non-valved elbow presents 2 (minor) issues:

     •        There will be a reduction in maximum air-conditioning performance, but the amount is not known yet (it may not be significant).  The mix/blend door is metal, so this should be ok to block heat (from the core when the door is fully closed and coolant is running through at 100%), but adding foil tape to heater core side of the door will help contain the heat when in MAX-AC mode.  Otherwise, the blend/mix of cold air will need be a little lower to get the same temperature previously (with the valved elbow) because the air mix from the hot side will be hotter with all of the coolant flowing vs partially with the valved elbow.

     •        If the radiator core leaks, you cannot put max ac on to close the valve and prevent coolant from flowing to it.


     •        heater cores may be better made than in years past, so leaking may not be an issue. 

     •        These cars aren’t driven much anymore, so this may not be as much of an issue.



Aftermarket Elbow pipe solutions (aftermarket defined as: not Nissan branded)

  • OEM: S13 240SX (89-94) and Z32 300ZX aftermarket and R32 Skyline are the same, but the (LHD, USDM/NAM) 240sx elbows need to be flipped 180° to be used on an R32 Skyline, if they’re still included with their cores.  You can still get 240SX model cores and plastic elbows from parts stores like RockAuto, but I recommend getting a core with the foam seals around it for better performance.  These kits are significantly cheaper than other alternatives.  Note this aftermarket kit for a 1990 240SX (USDM) does not have the foam seals, but has the correct elbows, and likely uses a simple O-ring gasket vs the OEM rectangle profile ring:


  • If you get a complete aftermarket core with the plastic elbows, they’ll likely come with the seals needed under the elbows. If not, they are Nissan PN: 92232-71L00.
  • R33/4: 93-97 Altima and R33/4, C34 have the same heater core, but the Altima elbows (LHD, USDM, NAM) need to be flipped 180° to be used on an R33/4, C34.  You can find these for significantly cheaper than OEM R33 branded parts.
  • Per one of the main skyline parts venders, there is a Cold vs Non-Cold region version of the R33/4 heater core, but I am not certain what the difference is.
  • Note this aftermarket 94 Altima kit has everything you need, foam, elbows and seals.  


  • OEM+: eBay seller “flat4gd” makes a welded 2-pc S13 aluminum elbow, which can only be used with the OEM-type hoses.  This kit does not include seals at this time.
  • Some pictures and video installed:




  • Performance: Boostdoc in Australia makes a single-piece CNC’d aluminum elbow design for the R33/4 C34, and (at the time of writing) soon one the S13/R32.  This design is very robust and has an M16x1.5 threaded end to attach a barb (16mm), AN fitting or banjo fitting to.  The kit comes with new seals, which is a nice bonus. 



Aftermarket Core Designs

  • https://www.skylineowners.com/threads/is-the-heater-matrix-from-r32-same-as-r33-r34.161484/
  • From this thread, the core is the same (or at least very similar in dimensions) from many 89-02ish Nissan vehicles, which helps keep the cost low for the aftermarket. 
  • The 240SX core works in an R32, which therefore means that all 240sx and Altima cores work in all R32-R34, C34, Laurel, 300zx, and other 90’s Nissan vehicles.
  •  I did measure the oem r32 core at 37mm, and the aftermarket Altima core at 41mm, but given the amount of wiggle-room in the R32 core housing, the Altima core should fit, and therefore it should fit in the R33/4.  At this time of writing, I’ll need someone to confirm that though – please IM me if you do!
  • R32 OEM vs S13 Aftermarket core:


  • R32 OEM vs 93 Altima core:


  • There is an aftermarket company on eBay, Conceptua Concepts LTD out of the UK that makes a core, but it is designed with a 3ish degree parallelogram shaped core, instead of a perfectly square one.  I tried it on my R32, but it causes the core to sit in the chamber crooked, with the top elbow sitting subflush, and the bottom to be slightly proud.  There is some buffer room in the fire-wall seals, but ultimately not enough for the plastic elbows to seat properly.  It difficult to see, but I was able to screw them down, but there was a static bending moment/torque in the elbows that I fear they would crack from fatigue (stress) over time, either at the base or in the neck at the bend.  I’m an engineer, but not an HVAC specialist, but my judgment says that these parts shouldn’t be under any kind of static stress.  So with something as difficult to get to as a heater core, it’s just not worth it to me to use this core, even with metal elbows.  I appreciate the attempt, but at 5x the cost of rock-auto parts, I just don’t see the value anymore.  Maybe it works better on the R33’s… however, it is already theoretically proven that 240sx cores work in R33’s.
  • Video on R32 Fitment: https://youtu.be/DybtA0AE8Qw



NOTE: If these images go dead, please send me an IM!

Edited by NoGrip61
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The R33/R34 lost the valve on the heater core due to cost cutting. Their grand solution to this problem is to simply keep airflow from going through the heater core with the blend door. One thing I've noticed is that the cabin on the R33 feels like it warms up more than it should and I suspect the lack of a valve to keep the heater core from warming up the dash is probably part of it.

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  • 9 months later...

Just did this job on my 32 with the boost doc kit.

was quite simple to fit, hardest part was getting the rubber bungs back on the firewall.

does anyone know how the heater will work now without the flap in the bend? Will I just have a heater on 24/7 now?

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On 6/9/2024 at 2:41 AM, Jonesy93 said:

does anyone know how the heater will work now without the flap in the bend? Will I just have a heater on 24/7 now?

It should still be able to be modulated with the hot/cold settings, but the adjustments may be a little different towards hot or cold now.  

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