Editing Z31/HVACReconditioning php (section)

== Z31 Heating and Air Conditioning Refreshing ==

The HVAC system in my 300zx was in pretty bad condition. The heater core leaked, the AC blows only warm air, and the temperature reading is often inaccurate. I decided, since I have to replace the heater core, I might as well completely renovate the entire HVAC system. I have included heater box renovation, duct repair, sensor repair, etc on this page. Again, if anything is missing, please feel free to contact me.

==== Items needed ====

* Spray enamel (flat black)
* Open cell foam weather stripping (3/8" wide x 3/16" thick)
* Number 3 steel wool
* Silicon spray lubricant
* Multi-purpose grease
* High temp engine enamel (cast aluminum)
* Metric o-ring
* 5 minute epoxy
* Soldering iron
* Rosin core (60/40) solder
* Ohm meter

==== Access the heater box ====

The heater core on my 300ZX was leaking substantially. To replace it, the entire dashboard must be removed.

-
Remove the dash from the vehicle (
[[Z31/DashboardRemoval php|Refer to the dash removal section for procedure]]). -
Remove the HVAC ducting (
[[Z31/heatercorereplacement php|Refer to the Replace your heater core procedure]]).

==== Rebuild the heater box ====

https://dev.z31library.com/xenonzcar_archive/z31/images/Raredare1/hvac/heaterbox.jpg

* If necessary, replace the flap seals within the box.
-
Remove the vacuum actuators from the right side of the box (see image below), including springs and vacuum manifold.

* Remove the vacuum actuators from the back side of the box, including wiring harness and sensor.
* Remove the six screws holding the two halves of the box together.
* Pull the box apart.
* Replace the internal flap seals.
* Scrape off all of the old seal.
* Sand the metal flaps with 220 grit wet-or-dry sandpaper.
* Repaint the flaps with spray enamel (Duplicolor high temperature cast aluminum engine enamel recommended).
* Replace the seals using open-cell foam weather stripping (3/8" wide x 3/16" tall).
* Lubricate all flap pivot points with a high-temp multipurpose grease.
* Reassemble the heater box.
* Replace all springs (optional, but recommended if springs are original).
* Lubricate all external pivot points with multipurpose grease.

==== Replace all vacuum lines ====

https://dev.z31library.com/xenonzcar_archive/z31/images/Raredare1/hvac/heaterbox2.jpg

* Replace all vacuum hoses on the heater box, regardless of their condition. (This is a must—you do not want to repeat this job!)
* Remove each vacuum hose and cut a new hose to match the original length.
* Replace one vacuum hose at a time to ensure correct routing.

==== Refinish the cross member and cross member center support brackets ====

* Sand the cross member with 220 grit sandpaper.
* Paint with flat black spray enamel.
* Reinstall the cross member in the vehicle. If needed, loosen the lower steering column bolts to assist with replacing the upper column bolts.

==== Rebuild the HVAC ducting ====

https://dev.z31library.com/xenonzcar_archive/z31/images/Raredare1/hvac/duct2.jpg

* Thoroughly clean the ducting, inside and out, using dishwashing detergent.
* Trim off any excess material left from the original molding process (see image above).
* Remove all traces of old weather-stripping.
* Mask the area surrounding the metal attachment brackets.
-
Refinish the metal brackets and all metal surfaces with flat black spray enamel (to match the cross member finish).

-
Apply open cell foam weather-stripping to all mating surfaces of the duct.

==== Sensor diagnosis and renovation ====

If your digital HVAC system is not working properly, refer to the
[[Z31/z31fsm php|Specification chart from 1984-1988 Nissan 300ZX Factory Service Manual]]
or the
[[Z31/Automaticclimatecontroldiag php|Z31 Automatic Digital Climate Control Testing procedure]]
to isolate any malfunctioning sensor. My system was functioning properly, but the sensors still needed restoration.

==== Final Assembly ====

* Reinstall the HVAC ductwork. Ensure all duct joints fit securely and are properly sealed. If needed, remove the 3/8" weather stripping and use a thicker open-cell foam for better sealing.
* Reinstall the center support brackets.
* Reinstall the dashboard.
* Test the HVAC unit to verify all positions and functions are working properly.

=== Sources Used ===

[[Z31/z31fsm php|1984-1988 Nissan 300ZX Factory Service Manual]]
* Writen by: Raredare

[[Category:Imported from Xenonzcar]]