New Heater/AC box question January 2025

Frederick Cahn

New Member
Good Morning,

I am in the midst of a teardown of my 1970 P6 3500S NADA. I am de-contenting the car and next up is the AC. I am looking for a non-AC heater box in usable condition with all the controls -levers, knobs, etc, and I am happy to supply my AC unit along with all the brackets and other parts.

I am also looking to buy a non-AC box and parts outright. Failing that, is there anyone who has simply removed the AC parts and run the unit as heater only?

Thanks in advance.
 
The ducting for the Air Con unit is different on the non- air con cars. They are also fundamentally different in operation. The Heater cars use fresh air all the time whereas the Air Con cars use mostly recycled air. The problem is the metal duct both units sit on is different and built into the car chassis cross member. The air con car has two ducts on the bottom - one inlet and one outlet. The Heater cars just have a slightly shorter outlet only. The heating on the air con cars can be used without the air con though. I think the main switch does not work the fan so by turning it off you can just have the heating (though the defrost function won't be quite as effective). In addition to the heater box you will need a complete centre console and the power windows only face plate which are very very rare. this is because the Air con cars faceplate blocks the slots for the operating levers of the heater only console. Another consequence may also be the loss of the centre air vent...Oh and there is a shim behind the front left road wheel spring which needs to be removed once the compressor and bracketry is removed so the car sits level.
 
The ducting for the Air Con unit is different on the non- air con cars. They are also fundamentally different in operation. The Heater cars use fresh air all the time whereas the Air Con cars use mostly recycled air. The problem is the metal duct both units sit on is different and built into the car chassis cross member. The air con car has two ducts on the bottom - one inlet and one outlet. The Heater cars just have a slightly shorter outlet only. The heating on the air con cars can be used without the air con though. I think the main switch does not work the fan so by turning it off you can just have the heating (though the defrost function won't be quite as effective). In addition to the heater box you will need a complete centre console and the power windows only face plate which are very very rare. this is because the Air con cars faceplate blocks the slots for the operating levers of the heater only console. Another consequence may also be the loss of the centre air vent...Oh and there is a shim behind the front left road wheel spring which needs to be removed once the compressor and bracketry is removed so the car sits level.
Wow...thanks Mike. That is clear and understandable. I think I will go ahead and take everything out of the box and replace only the overhauled heater parts. Hopefully the door actuators will still function. I have even thought of removing it all, blocking off all the engine compartment ports, and adopting a Vintage Air heater only kit. I used an AC one in this manner previously with satisfactory results on a 1961 Galaxie.

I appreciate the info about the shim; that would have really puzzled me! I am actually concerned about the weight I have removed from the engine compartment. Entire fuel induction system (replaced with correct 62 Buick 4Jet and intake), AC, power steering (now a NOS manual steering box) , etc. I think I might have to replace the springs or cut them down.
 
I'd be inclined to leave the air con core in the box and just disconnect the lines at the Tx valve/return. Getting the two cores out involves hundreds of small screws and rivets and you need to disconnect all the wiring and tubes that go into cabin and are all connected individually to their switches etc. There are a couple of 1968 manuals on Ebay at the moment which have the complete wiring diagrams and pneumatic plumbing for NADA V8s in it.

The purpose of the shim was to compensate for the compressor weight hence need to remove.

Unlike most car ventilation systems the rover ducting is upside down. There are two sets of exit ducts (as usual, one above the other at the firewall) but the screen vents are fed from the Lower duct while the face vents are the upper ones. There is also zero room behind the dash. its only as thick as the top shelf is deep. This makes changing the heating or cooling to aftermarket units problematic.

The power windows use a completely different circuit and harness. Bar wiring all the components are ex GM of around 1969 vintage. You can get new switches online cheaply and there is a company over your way that rebuilds the motors. The mechanism is the US one patched onto the original Rover window frame. Glass should be automatically tinting sundym (all round). The hard to get piece is the centre console face plate which tend to become brittle over time and crack in several places but they have a unique way of lighting the switches through the plastic.
 
Thanks Mike. I found significant rust on the box so I shipped it off to Alexandria for an overhaul (if it gets through British customs). Really appreciate your sharing of information.

All the best!
 
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