Among the several upgrades that may be done to an older car to make it more civilized, the inclusion of a contemporary climate-control system has to be at the top of the list. Going to a rod run on a hot day without A/C can feel like going in a mobile sauna or, when the weather turns chilly, a refrigerator without a heater.
When it comes to installing an aftermarket climate control system, there are two basic types: universal systems and vehicle-specific systems. However, regardless of the sort of system deployed, the same constituent components are used and function identically.
The air conditioning system’s evaporator and expansion valve are positioned in the passenger compartment, typically behind the dashboard. It absorbs heat/humidity, and the expansion valve regulates refrigerant flow; the compressor is powered by the engine and circulates refrigerant throughout the system; the condenser is mounted in front of the radiator and cools the refrigerant, converting it from a gas to a liquid; the receiver/drier filters refrigerant separates vapor from the liquid refrigerant, and removes moisture; The thermostat regulates the compressor’s cycle time.
For people who live in areas other than Southern California who are occasionally subjected to brass-monkey conditions, the heater/defroster component of a climate-control system can be critical as well. It comprises essentially a small radiator-style heater core located inside the evaporator case, hoses transporting coolant to and from the core, and a control valve.
Basic advice to people building an older car and intending to install A/C later: Place the engine in such a way that the radiator, condenser, fan, and shroud all have sufficient clearance. It is far more convenient to plan ahead than it is to make modifications later.
When searching for a system, we’ve always found that purchasing a whole kit is the best option. This avoids the chance of malfunctioning components, such as incompatible condensers and evaporators. Additionally, most vendors recommend choosing the largest evaporator available when selecting a climate-control system. That is, it is preferable to have a large system that does not have to work as hard to accomplish its mission as it is to have a small system that struggles to accomplish its mission.
Because an A/C system cools the passenger compartment by eliminating heat, it stands to reason that increased heat makes the A/C system’s task that much more difficult. The firewall, floor, doors, and roof, as well as all other external heat sources, should be insulated to avoid temperature gain in the passenger compartment. Additionally, all door and window seals should be completely leak-proof. Insulating and sealing an early automobile might be difficult.
Evaporator: Never plug unneeded evaporator outlets during installation, as this can result in localized freezing of the condenser coil. Outlets that are not in use should be left open. They may be equipped with short hoses or specialized ducts that allow them to discharge behind or beneath the dash. Additionally, avoid completely sealing off the under dash and restricting airflow to the fan.
Condenser: Proper installation of the condenser is crucial. The refrigerant pushed from the compressor must be on top and the liquid line must be on the bottom. The condenser should be installed in the airstream near to but not contacting the radiator. Utilize a high-capacity fan and shroud.
Receiver/Drier: These are marked with an arrow indicating the flow direction and must be installed within 30 degrees of vertical to preserve the liquid seal.
Compressor: Sturdy brackets and proper alignment of the pulleys are crucial. The drive belt should wrap around at least one-third of the pulley and contact and drive on the pulley’s sides, not bottoming out in the groove.
R-134a refrigerant is used in modern air condition systems. Due to the tiny size of its molecules, it requires O-ring fittings and a crimped barrier hose. A/C hoses are available in three sizes: #6 liquid from the condenser to the evaporator; #8 liquid from the compressor to the condenser; and #10 suction hose from the evaporator to the compressor. Hoses for heaters are 5/8 inch in diameter.
Safety Switches: Excessive high side pressure can result in compressor damage or hose breakage. When the refrigerant and pressure in the system are lost, the compressor’s lubrication supply is also lost, which can result in the compressor being damaged or seizing. A binary safety switch safeguards the system against both high and low pressures. A trinary switch incorporates both high and low protection, as well as an electric fan engagement indication operating at 254 psi.
Heater Control Valve: The majority of heater control valves are directional and must be installed in the high-pressure heater line in the proper orientation. Due to the fact that water pressure in the hose assists the valve in sealing, if they are fitted incorrectly or in the incorrect hose, they will not totally shut off and some hot water will continue to flow.
Electrical System: Many modern air conditioning systems have sophisticated electronics that can fail if not connected to a steady power supply and grounded properly, thereby eliminating the chance of electrical feedback that could result in unpredictable functioning. A reliable electrical source is required for sophisticated, electronically controlled air conditioning devices. Additionally, the engine, chassis, body, and batteries should all have appropriate ground wires, and the alternator should be capable of supplying enough power to operate the A/C system and any additional electric fans.
Evacuating the system for 45 to 60 minutes with a vacuum pump removes air from the system and lowers the boiling point of water, causing any moisture in the system to boil away. 1.8 pounds of refrigerant is required to charge a basic system. To detect whether it is correctly charged, gauges that display low and high side pressures are required. As a general rule, high-side pressure should equal twice the ambient temperature plus 15-20% and low-side pressure should equal 18-20 at 1,500 rpm with a strong shop fan blowing into the condenser to imitate road conditions. Overcharging a system leads to increased system operating pressures and decreased performance. A system that is undercharged will exhibit lower operating pressures and poor performance. Keep in mind that when the A/C evaporator and heater core are installed together, antifreeze must be used to prevent the heater circuit from freezing.