HVAC / DCC Discussion (S13 Only)

[ixfxi]

In case anyone wants to tear into their HVAC system a little deeper, I am sharing some recent photos of the work I have done to rejuvenate the gaskets and clean everything up before re-assembling in the car. I plan for this thread to cover the entire HVAC system, from A-to-Z.

I wont be going into the AC part of the system for a (long) while, but if you guys ever feel like elaborating... by all means, please add to the discussion. I have gone back and fourth on AC or NO AC for a long while now. Being that I have an SR20DET, I am ditching the AC (for now) for a list of reasons:

1) I already have too much plumbing in the engine bay that is higher priority and will possibly interfere with the OEM AC components: oil cooler + ducting, intercooler + piping, headlight components, and other things.

2) The OEM setup requires a mix of USDM and JDM parts. I am not ready to deal with brazing fittings and would like to look into using alternative (smaller or more universal) parts later down the road. In the future, I will look into what condensers or driers are available.

3) I still like the clean, empty engine bay look. So I'm going to try to keep it like this as long as I can manage being without AC.

In the meantime, here are some photos that show the internals of the HVAC system:

^ HVAC components + ducts


^ Main HVAC housing which stores the heater core, hot/cold blend door, and also controls the air adjustments.


^ This is the duct that stores the AC evaporator. With no AC, I have removed the evaporator and styrofoam insulation. The evaporator inlet/outlet holes were plugged and sealed, as was the drain tube.


^ This is the blower motor housing. On the bottom side is the fan. The top has the recirc door and servo.


^ These are the plugged holes for the evaporator.


^ New foam seals for the position flaps and upper duct seal.


^ Close up of new foam.


^ Close up of OLD foam. Its rotten and will disintegrate upon touch.

I used McMaster for the weather resistant foam. I thoroughly cleaned the interior and exterior of the HVAC system, I highly suggest doing the same. As you would imagine, a lot of junk accumulates over the course of 20+ years.

[ixfxi]

Also, I am going to temporarily host these photos but want to ask the mods/admins if they can boost my storage for attachments? It would help so that we can properly archive these photos so that they do not fall by the wayside.

[KAT-PWR]

I'd recommend photobucket if its too much hassle for mods. I have 1500 pics over the course of like 8 years. The photos i have posted on other forums are still in threads from early 2000's. Also super easy to upload and post via smartphone.
There is literally nothing worst then finding a thread with good information and informative posts only to have the accompanying photos gone

[ixfxi]

Yeah, I understand. But hosting is not the issue here. A forum is supposed to be a knowledge base of information. If its text without the photos, then the forum is less useful. The attachment limit appears to be just over 5mb. For today's standards this is a total joke.

[KiLLeR2001]

Nice, I will have to get new foam, all of my HVAC shit is out right now so might as well. I welded my A/C holes shut in the firewall so I'm not ever going to worry about it. However, I will need to have my blower fans and heat still installed.

Do you know if Nissan still offers new heater cores? If so I'd like to replace mine because that plastic is a ticking time bomb for cracks.

[ixfxi]

I believe the heater core is still available. I inspected mine and it appears to be in very good condition. I was pretty good about changing coolant and with the lower temp thermostat, my car never really ran high temp / pressure. Even the heater core end tanks are light in color as opposed to the dark, worn plastic look that most get as they age. If I was smart I would buy one, but as you know I am a moron.


^ Here is a (stolen from ebay) photo that shows the linkage from the blend door TO the heater core.


^ In specific, this photo shows the heater core's integrated shut off valve. It is important to make note of this because when you turn the HVAC to "COLD" setting, the blend door closes access to the heater core AND simultaneously disables the heater core. When that valve is closed, the heater core is no longer receiving piping hot coolant.

[rant] If there are any unfortunate Miata owners here, this is an important tid-bit that I found over the years as the Miata does not have a heater control valve. In essence, the Miata's heater core is ALWAYS active and therefor, when you drive you still feel heat from the vents even if your HVAC is set to COLD. The only time you actually get COLD air is if you enable the AC. The AC is cold enough to eliminate most of the heat generated from the heater core, but still... I've always found that the AC in the Miata was barely sufficient, and its probably due to the heater core being always active. Just one of the many reasons I think Mazdas are inferior [/end rant].

[zupabpoor]

The photos i have posted on other forums are still in threads from early 2000's. Also super easy to upload and post via smartphone.

[d3m14n]

Do you have a part number for the foam?

[w0nderbr3ad]

Subbed.

I've been meaning to do something about my AC Evap since removing my AC years ago, but slowly becoming lazy seahag.

[ixfxi]

There are various thicknesses foams needed. I advise that you measure and come to your own conclusions. However, I will share with you the ones that I used the most:
93725K64
93725K52
8694K137

The less expensive foam McMaster sells is a pain in the ass. Its rated up to 158°F. Not only is the foam fairly stiff, but the "rubber based" adhesive is fucking annoying. Once it sticks to something, it is insanely difficult to remove. Dont be cheap, pay for the more expensive 220° foam. This uses an acrylic based adhesive which is similar, if not identical to stock.

I went ahead and fit most of the HVAC parts back into the car today, its all so nice and clean and restored -- really put a smile on my face.

A couple things I would like to ask:
Does anyone have a PN for the heater core grommets and foam insulators? I searched and it appears these parts are NLA, maybe I am missing something.

FYI, the heater core comes up ~$150 at Courtesy Parts.

[KiLLeR2001]

Nissan Part#: 27177-35F00

That is for the circular grommets that go around the tubes.