Car Restoration Projects
Fitting an air conditioner to an historic vehicle
For this guide we’re indebted to Brian J and Queensland’s Blackall Range Horseless Carriage Club. The subject vehicle was Brian’s beautiful 1957 resto-mod Jaguar XK150 Coupe.
We know that Enzo Ferrari reckoned the Jaguar E-Type was the most beautiful car in the world, but some in the Historic Vehicles team are more inclined to give the Jaguar beauty quest honours to the XK150 Coupe. Its combination of gracefully integrated headlights, oval grille, curved one-piece windscreen and elegant hardtop are hard to beat, they reckon.
Brian J, of the BRHCC, is devoted to his XK150, but not to the point of period accuracy overriding functionality. His changes to the standard specification when he restored this machine included a five-speed gearbox, Vicarage power steering conversion and better seating.
“I was happy with the car’s enhanced drivIng characteristics,“ Brian told Historic Vehicles. “But there was one issue that needed further attention, to improve my comfort and that of my passenger – ventilation.
“Being in Queensland, there was no way that on our Club runs I would arrive as relaxed and cool as those who had modern sedans, so air conditioning beckoned.”
Brian did his research and quickly came to the realisation that a normal, belt-driven-compressor-type aircon unit wasn’t going to do the job.
“Conventional systems operated via a belt-driven compressor, but that was not feasible, as the only space available in the engine compartment was occupied by a power steering pump under an alternator,” Brian explained.
“Would I refit the original manual steering rack assembly?” he mused. “Then change the belt pulleys and fan setup, to mount a compressor, clutch and belt drive and lose the most acceptable steering features…
“Not bloody likely!”
Yet another approach he checked out was replacing the hydraulic power steering kit with a new electric power steering assembly.
It seemed to be possible, because there was adequate space under the dash for the drive unit, if a bit restrictive in terms of knee room, but there was inadequate space in the engine bay.
At this point, Brian J realised that an all-electric aircon system was his most likely route. Components would consist of compressor, under-dash evaporator and fans, control systems and a condenser.
Brian reckoned that the existing HVAC unit would work with aircon input, but there would be a need for additional controls, depending on the compressor choice. He also decided in favour of Minus 20, rather than R134a fluid, because it wasn’t a CFC, was compatible with most aircon systems and was readily available.
The electric compressor types available were 12-volt units designed for hybrid and electric cars. Some had integral controls and others required external systems.
Most compressors were three-phase AC powered, from inverters, but direct DC motors were rare in the power range needed.
A wide-ranging search showed that new aircon systems from OEM spare parts stocks – mainly Toyota and Honda – were very expensive.
It wasn’t looking too good until Brian came across a Korean manufacturer, NEK, who could provide all the Items required for the plant, including the main controls and cabling, with a complete system description.
The total imported component cost was competitive with an equivalent, mechanically driven system.
Additional parts needed included hoses, line fittings, fans, additional cables and mounting hardware that were all purchased locally. Brian also bought a gas handing kit, with gauges, hose terminations and crimping tools.
“Because the aircon’s continuous running load was 50 amps,” Brian said. “It was necessary to fit independent battery supply cabling and replace the alternator with one rated at 70 amps.
“This alternator can be seen sitting fairly high on the kerb-side of the motor, with minimal clearance from the body.
“It is well that the engine mounts are firm!” laughed Brian.
The condenser was from a 2000MY Honda Civic, having the required physical dimensions and capacity, with preferred vapour and liquid connections. However, its standard fan was replaced by a slim 300mm unit, which provided adequate airflow and the receiver/drier was mounted in front, just clearing the radiator grille.
To manage the lncreased heat load, the radiator was given a strip and clean, and then fitted with a 400mm 12-volt fan on the engine side. That meant replacing the original fan with one from an X300.
“The engine fan is adequate for engine cooling unassisted,” said Brian. “When the aircon is not in use.”
To be on the safe side, the compressor sitting adjacent to the exhaust manifold required a heat shield, for thermal protection.
“It has integrated overtemp and overload protection,” Brian said. “But neither function has never been initiated.”
The control system incorporated fault alarm Indication, by way of flash pulses of the alarm LED. The alarm LED pulses are triggered by excessive current – over 50A; under-voltage; locked rotor; electric fan fault; lack of electric motor phase; compressor over-heat and pressure switch protection.
Setting up the aircon system was a tad tricky and involved loading the hydrocarbon thermal fluid in stages, while monitoring pressures and testing for leaks.
“We took great care of eye protection, as well as taking precautions against fire,” said Brian J.
When the system was considered stable, operating parameters showed in the recommended ranges, until the system protection shut down because of low voltage. At that point, the engine’s new 70-amp alternator provided the required energy.
Brian J is very happy with e electric aircon system in his XK150, although he can’t vouch for how it would work in a larger-volume sedan interior.
“The nominal heat transfer is limited to 1500 watts with this 12-volt compressor, so a higher capacity 24-volt model may be needed in larger vehicles.”
Historic Vehicles is grateful to Brian J and the Blackall Range Horseless Carriage Club for permission to run this edited article and we hope it’s of use to other comfort-seeking historic vehicle owners.