Since I intend to be able to drive this project anywhere and anytime (winter excluded!) having a fully functioning HVAC system is important. I was planning to use the 720 dash for a variety of reasons but ran into a large (or perhaps small depending on your perspective) problem because of the difference in HVAC systems between the 2 generations.
As the 720 features 4 dash air vents with heated or cooled air plus 2 side window vents in addition to the defroster ducts, there is way more ducting to fit behind the dash than the very basic and simple 620 heater that only ducts to the defrost. There is just no room for all this ductwork.
- HVAC from 720
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Compounding the problem is the 720 blower assembly physically mounts & draws air in on the far right side vs. the 620 central air draw. I was hoping to have the option of adding in AC (available on the 720/unheard of on the 620) but this just won't be possible. The solution options were to "fit" the 620 combination unit to the 720 dash but not have functioning dash vents, or to return to the 620 dash and forego the other benefits of the 720 dash PLUS be forced to modify the wiring harness to adapt to the 620 instrument pod.
I have decided to go back to the 620 dash and have refurbished the original heater assembly, upgrading it as possible to gain more CFM airflow and introduce more fan speeds. The heater core is no longer available, thankfully the original tested good and only needed a very thorough cleaning, plus unseizing the water control valve. The 720 fan motor was modified to fit and the housing modified to accept the larger heater electricl block plus duct in the motor draft tube. The 720 hamster wheel fan was just slightly too large - a few mm in diameter - so the original fan was retained. The old heater now features a higher RPM motor and the 4 fan speeds from the 720.
- blowers
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- heater core
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- motor side
- IMG_8152 small.jpg (190.74 KiB) Viewed 1515 times
- completed
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More work and updates to follow...