HVAC rebuild

[GTVeloce]

Just finished rebuilding the HVAC from the GTV. There was quite a bit that needed repair and replacement. There was a number of cracks in the housing which needed repair. All the foam had perished (not surprising after 35+ years). The thermostat needed to be replaced. Other things I did to improve it were;

• additional closed cell foam (I used dynaliner) inside the unit to reduce noise and vibrations and ensure the heat/cold go where it is supposed to and not elsewhere
• LED lights
• replaced the blower fan controller and resisters with a PWM device so my fan speed is infinitely controllable.
• replaced the heater hoses that pass through the firewall with buklhead connectors and new hoses
• removed and cleaned the evaporator and AC hoses in preparation for a full rebuild of the AC circuit (including new parallel flow condenser)
• put foam pieces on either side of the feet flap so it doesn't make that awful clunk sound everytime you operate it

Bench tested everything and very happy with the result. The fan is off when the switch is off but after a few degrees of movement the fan very slowly begins to turn, ramping up to full speed after about 180o of rotation of the knob.

Previously I had replaced the resisters with the 75 style ones which were better as the lowest setting was too fast for my liking but this is even better. A bit of fiddling around to make it work. The unit is off ebay but the pot that came with it was too small (physically) and the wiring too short as I wanted to mount the device outside the HVAC unit. Extended the wires and installed a bigger pot (Jaycar). Then had to grind the pot down so that the original fan knob would fit (I wanted it to look factory inside the car).

[Anth73]

Love your work! I've wondered if anyone has tried 3D printing a new heater / AC housing but redesigned the internals so that it operates a pusher fan and more efficient evaporator?

[GTVeloce]

I did look at that while I had it apart. I think the answer would involve (assuming you are trying to keep it looking fairly original) adding an external single barrel fan under the glovebox (or instead of) that feeds into the rear of the HVAC unit. A more efficient evaporator in the same location and then you would have space to setup a blend door and a smaller heater matrix setup at an angle to the evaporator. Air is then pushed by the fan through the evaporator and is then directed either through or around the heater (or part thereof) depending on temperature required. This would also mean the heater tap would no longer be needed cleaning up the interior and removing a common failure point.

I decided I wasn't happy with how much force was required to operate the heater tap on my current setup so bought a bicycle brake cable and used the outer sheath to replace the original. Much easier to slide now.

[MD]

There is an extensive discussion on 116 air issue in the topic that I started in 2009. Perhaps you have not seen it. Lots of information regarding the total problems with these systems.

Must be a common problem, it has been read over 13,000 times.

https://www.alfaclubvic.org.au/forum/index.php?topic=2990.0

[John.Heidemann]

My GTV6 didn't have the aircon onboard when I found it but putting it back in is still on my wishlist. Thanks for all the tips.

[GTVeloce]

My AC rebuild is setup as such;

• Sanden SD5 Compressor
• New, larger, aluminium parallel flow condensor
• New receiver dryer
• New 134A compatible O-rings
• re-routed hoses and quick coupling service ports
• cleaned but standard evaporator
• rebuilt HVAC unit to try and improve air flow and attenuate noise
• standard TX valve
• Gassed with HyChill HR12
• improved heat insulation inside cabin and heat shields in engine bay and above exhaust
• UV max tinting
• thermostat adjusted to reduce fluctuations

Many of these things MD has mentioned in his posts. I haven't gone to some of the lengths as I am trying to maintain a mostly factory look inside the cabin. I am also toying with blocking off the fresh air vents on the side as they just duct hot air and I never use them. Ideally I would like to run ducting from the HVAC unit to the side air vents but I'm not confident there is room without major modifications.

Last year I had to recover the headliner on my 75 and while it was off I covered the roof in heat resistant lining (dynaliner) which made a big difference to heat load in the car. Would like to do the same on the GTV but don't want to take the headlining off!