This is part 1 of a series of posts to document some of the stuff I did to fix my HVAC.
At this point what’s done:
- Rebuilt heater core box and blower/air intake box. Currently they are back in the car but not the evap box, vents or dash. This involved replacing all 3 actuators with cheap aftermarket ones. The 3 bellows were still functioning.
- Disassembled/reassembled vacuum pump and vacuum tank and lubricated orings (ideally you should replace these)
- Replaced AC compressor
And what still needs to be done:
- Rebuild evap (replace orings), put evap box back into car
- Replace o-rings on everything in the engine bay
- Charge AC system / final tests
Quick Background
My Z’s heater and AC didn’t work when I first got it. On top of that the thermostat got stuck at one point and ruptured a leak on the heater core. So until recently I had bypassed the heater core to prevent flooding my interior.
Since I live in TX I wanted A/C so I can drive the car any time of the year. But this car is R12/freon so first my plan was to replace all of the o-rings with HNBA so I could convert to r134a. Part of this job requires removing the A/C evap in the car to replace all of its o-rings. This requires removing the dash and all of the vents. While I’m in there I may as well fix the heater core. And on top of this, spoiler alert, almost none of the vacuum actuators were functional. So time to fix all of that. The goal of this page is to 1) list out some of the aftermarket parts I used and how I made them work and 2) dump a lot of reference photos.
The project isn’t done yet (few more weeks) but the heater box is fully functioning and reinstalled at this point.
Stuff I Had To Buy
A large amount of the job was just dismantling stuff, cleaning it, lubricating, and putting back together. All of the old foam was either worn away or super brittle and useless. I cleaned that off and replaced with various weather stripping foams from Walmart / Amazon (maybe $30 worth in the end).
I purchased all of the cheap Dorman vacuum actuators I could find on Amazon to see what could work where. In the end I was able to make all 3 of these work and didn’t have to buy any others. 2/3 of the ones I bought were Amazon warehouse deals and extra cheap – both normally closer to $15. Buying functional used actuators is closer to $100/each. For all 3 I had to manually design/3d print some mounts so that these actuators would work. 2/3 I had to modify in some way (saw off some of the linkage and/or bend linkage, clip off some of the plastic mount area)
First I purchased an HNBR o-ring kit from RockAuto, but this was useless. Just buy a $5 harbor freight assortment. There are a few sizes of o-rings you’ll need beyond that though and I got those from the O-Ring Store. These are in the evap. You need 2x of the 026 size and only 1x of the other two. I got the Viton one because the HNBR minimum quantity was like 250. Shipping cost more than the o-rings.
At first I ordered a heater core that was recommended for the Z but it was around $100. I ended up returning it and getting one from Amazon that I made work. It’s a little undersized but we’ll see if it heats up the car soon enough. I also ordered a relief valve since I’m not sure on the condition of the original. I also bought 50ft of vacuum line and used the majority of it. The vacuum pump is optional but was useful for troubleshooting.
| Item | Price |
| 57433 3Seasons/Everco/A/C Compressor | 308.49 |
| XtremepowerUS Vac Pump and Manifold Gauge Set | 129.50 |
| Spectra Premium 94576 Heater Core | 33.32 |
| Various weather stripping foam | 30.00 |
| 50ft Gates 27041 Vacuum Hose | 23.47 |
| 12V Vacuum Pump | 20.95 |
| Dorman 604-934 Vacuum Style Air Door Actuator | 15.89 |
| SW 2155C A/C Receiver Drier Pressure Relief Valve | 15.82 |
| 1x AS568-021 HNBR (HSN) Highly Saturated Nitrile 70 Duro O-Ring (H70021) | 8.50 |
| 2x AS568-026 HNBR (HSN) Highly Saturated Nitrile 70 Duro O-Ring (H70026) | |
| 1x AS568-029 GV75 Green Viton (FKM, Fluorocarbon) 75 Duro O-Ring (GV75029) | |
| 1311567 A/C System Valve Core and Cap Kit | 7.48 |
| RD1168C A/C Receiver Drier / Accumulator | 7.38 |
| Dorman OE Solutions 604-922 Vacuum Style Air Actuator | 6.77 |
| Dorman 604-933 Vacuum Style Air Door Actuator | 6.39 |
| Heater Core Firewall Grommet 90480-01405 ($3.70+S/H) | 11.11 |
| Misc (HF oring assortment, hose clamps, brushes, cleaners, etc) | 50.00 |
| Project Total | 613.96 |
Probably more expenses as I wrap up the project, but this is most of it.
Modifying and Mounting the New Actuators
Intake actuator – Dorman 604-934
3d printed mount: https://a360.co/2BFQEDM
This one was the easiest to use and mount. No need to modify the linkage, just remove the e-clip from the current one and swap. This one happens to be a 2 stage actuator just like the one it’s replacing. I’m not sure if the angle of the door is going to end up the same but hopefully it will work.
Power Servo 1 – Dorman 604-922
3d printed mount: https://a360.co/2BH1ysF
I sawed off the last 2 inches of so. Then I put a right angle and used the already drilled hole to butt against the existing hardware. I also used the mounting slots to attach the 3d printed mount.
Power Servo 2 – Dorman 604-933
3d printed mount: https://a360.co/2BHQCeJ
I had to cut off a few things from this one. First I trimmed all of the plastic off that is meant for mounting the actuator. Then I sawed off the last piece of the linkage.
This actuator had too much travel vs the original one. You can see in the picture above how I took care of that. The first 1/2 in of travel is doing nothing while the next 1 in of travel actuates the assembly.
Adapting the Heater Core
I sawed up a bunch of foam to make the profile of the smaller heater core fit in the slot. There are foam strips along the sides to make an air tight seal.
I still need to figure out mounting the solenoids for the air intake door.
Hey man, just wanted to say this was a huge help reworking the climate controls in my z31. Thank you so much for providing actual part numbers for everything. So many guides completely leave it out. In mine the two actuators on the back for the mix doors have a blown diaphragm, and this helped find some usable replacements.
Thank you for this writeup. I’ve had my Z for over 20 years and never had to go under the dash. When I finally did, thankfully, I found this posting and at least had some idea what could be done to fix the problems. Your resourcefulness and ingenuity are impressive, and extremely helpful. I do have few questions though.
Did you have any trouble changing the O-rings on the A/C evaporator / Expansion Valve / Suction Throttle Valve?
How has the Blower Intake Actuator worked out? Did you figure out a good way to connect the solenoids for the intake door? and How did that work out?
How has the Heater Core you chose worked out?
How have the 3D printed mounts held up?
What happened to “Part 2”?
Hopefully your Z’s heat and A/C is working great now, and hopefully mine will be soon too.
Again, Thank You – Thank You – Thank You, for writing this up and sharing it with us.
Part 2 will happen eventually. I’ll have a garage soon which will make it way nicer to work on the Z. I replaced all of the orings on the evap no problem, but I was lazy and didn’t pressure test it. Long story short I went to vacuum test the AC system and it wouldn’t pull vacuum due to a leak on the evap. So I have to pull the dash again soon…
I probably should reprint the 3d printed parts in PETG. These were PLA and that won’t hold up well to 100degF+ conditions.
The heat seems to work well but I haven’t used it much. I also live in TX so for the foreseeable future I won’t be using it much.
I’m sorry to hear about the leak in your evaporator. I wonder if it could be due to the size O-rings you used. When I researched the parts you listed I also checked the Nissan parts which note the metric sizes; 1 @ 25.5mm, 2 @ 33.5mm, and 1 @ 35mm. On the O-Ring Store website I ended up ordering; AS568-022 (25.12mm), AS568-027 (33.05mm), and AS568-028 (34.65mm). These are all HNBR, and all are available in quantities of 4 or 5. (If you want the extras I will get, let me know)
The thing I really want to know though is; How did you end up attaching the vacuum tubes and solenoids to the Dorman 604-934 actuator on the blower intake door? And how is that working?
Thanks again.
Any chance I can get an STL file for the actuator mounts? I have a Z31 in the Austin area and would like to replace some of the actuators on my Z.
No problem, I uploaded the STLs to thingiverse. https://www.thingiverse.com/thing:4879883/files
NIck,
I cant thank you enough for taking the time to share your knowledge with the Z31 community through this page. Especially loading the STLs. to thingverse so we can use your bracket models to print our own.. I just rebuilt my heater box and fan housing – all new foam on all doors, seals, etc, and I was able to send the bracket images to a printer (I do not have my own 3D printer), ordered the doorman actuators you described above and they all worked perfectly with your mounts. (including the intake actuator in the fan box — and I will confirm for anyone else that needs to do this that it does not require any modifications and travel is perfect {above is silent on final verdict so I wanted to share}) Never could have done this without your guide and bracket models
Cheers
Link appears to be broken. I get a 404 error.
Hi Nick, would it be possible if I can get a copy of the STL files as well? Thanks!
added them here https://www.printables.com/model/561572-1986-nissan-300zx-hvac-actuator-mounts
Awesome, thank you so much!
Great article. This us what I did. I have a 86′ 300zx with the round expansion valve that mounts on the evaporator. Two screws hold on a plate with the solid freon line. Takes 2 o rings to seal the expansion valve. Anyway, not to be had anywhere so I found a complete evaporator with a modern expansion valve. Off a 32 model. I was able to modify my original evap box for it to fit. Slip on fitting adapted the large pipe fitting off the original core so the new unit would bolt up. Works like a champ and new design expanson valve is readily avail for about $17. Original case bolts right up with new evaporator all sealed up with fiberglass. Just saying !!
New with my ’86 300zx but sooooo happy for this page.
Thank you!!