How To

Cooling Your Pony

  •  - 0
  • Print

provided by


by Tom Rounds  More from Author

Classic Auto Air Has the Perfect System

If your early-model didn’t come with factory air and you would like to add it, Classic Auto Air’s Original Ford Underdash A/C system is the answer. The system is designed to keep you cool and also be as Ford intended the A/C to be. With the exception of only a few minor details, everything in this kit looks exactly as Ford made it when the car was manufactured in ’65. Even with the condenser updated with 6-circuit tubing instead of the original 3-circuit tubing, the look remains the same. We also decided to upgrade the system with a Sanden compressor using 134a refrigerant.

Here’s how we installed the system in our ’65 convertible.

Classic Auto Air’s complete Original Ford Underdash A/C System (PN 20-118) for a 1965 V-8 Mustang. In our project car we took advantage of the Sanden compressor upgrade, this uses environmentally-safe 134a refrigerant instead of the original R12.

We started by removing the grill, hood latch assembly, and front valance. This allowed for access to the front of the radiator while installing the condenser, drier, and hoses.

Next we moved to the engine bay and removed the fan and crankshaft pulley, both will be replaced. 

The crankshaft gets a new pulley with three slots so an additional belt can be used. The new fan has an additional blade with a deeper pitch to supply a higher airflow for the condenser.

Because our project car’s engine has newer heads, the A/C compressor bracket needed to be enlarged from 3/8-inch to 7/16-inch. The bolt holes in the front of the heads on a ’79 and new have a larger, 7/16-inch hole.

We needed to slot the outside hole to make it possible for all five bolts to line up. This would not be necessary if the original heads were used.

With the A/C bracket in place, the Sanden compressor was bolted on.

In order to keep the fan belts properly aligned, when placing the A/C compressor onto the bracket. The mounting ears need to be positioned in front of the bracket tabs (arrows).

To make installation easier, the condenser/drier assembly can be put together on a workbench. Here we attached the four brackets, one in each corner to the condenser. The brackets are positioned on the condenser to line up with the radiator bolts and core support.

The brackets are located 10 ½-inches from top to bottom...

...and 18½-inches from side to side.

Next, the drier is clamped to the left side, or driver’s side of the condenser with the in flow and out flow tubes pointing downward. PLEASE NOTE – It is important to keep the filter-drier sealed and the opposite end of the condenser sealed until ready to connect hoses.

Once the condenser was assembled, it was installed on the car. Instead of using the original radiator bolts, the condenser brackets have studs that go through the radiator, core support, and the brackets for the fan shroud.

We placed the fan shroud brackets onto the condenser studs, one in each corner and tightened them.

A new six-blade fan was lowered onto the water pump and bolted in place.

Using one of the water pump mounting bolts, a cast bracket is bolted on that will hold an idler pulley. This will keep the fan belt from interfering with the water pump and be used to tighten the fan belt.

We used a belt tool to measure the tensioning on the fan belts. The belt should have a ½-inch deflection up and down from center.

In preparation for the under dash unit, we drilled a hole into the floor where the drain tube will be installed.

To supply power to the unit, a wire is attached to the back of the ignition switch so there will be power when the key is turned on.

The under dash unit, which contains the evaporator core, fan blower and operating switches comes pre-assembled from Classic Auto Air. Before installing in the car, we first attached the high- and low-pressure hoses and wrapped the fittings with insulated tape. The insulated tape prevents condensation buildup that would drip onto the carpet. Note – All the connections in this system are flare connections that do not require an O-ring. It is important to lightly lubricate both mating flare surfaces before assembling, and use two wrenches to tighten connections, holding one secure so as not to twist the fittings that do not rotate. Also, do not use any leak-lock or sealant tape to assist with leak prevention as these will only insure the flare fitting will leak.

Next, the under dash unit was positioned and bolted in using two bolts, one on each side. On the lower backside there is a bolt that makes contact with the floor, this is for leveling and stabilizing the unit.

The hoses are fed through a factory oval-shaped hole in the firewall just right of the master cylinder. If the car never had A/C, like ours, the oval hole needs to be punched out. This hole is scored from the factory and a blunt punch and hammer will knock it out. Also, through this same hole, a wire that controls the clutch on the front of the compressor was ran.

We finished the inside installation by attaching the drain hose.

Two 1¼-inch holes were drilled into the radiator core support, one at the top and one at the bottom. There are indentations in the metal where the factory holes should be. This makes placement exactly as Ford intended. The high and low pressure hoses going to the condenser were ran through these holes using rubber grommets to protect them.

We lubricated the O-ring and slid it on the hose fitting and attached it the compressor. It is important to lightly lubricate the O-ring before assembly.

As shown in this photo, the hoses should have a small bend and not be taut, this allows for engine movement.

A pressure switch is installed between the condenser and evaporator to prevent system damage. This switch will turn off the system if the high-pressure side drops below 28 psi and over 398 psi.

The last piece we connected was the wiring. The lead that comes from the firewall is attached to the pressure switch and then the compressor. The system is now completely assembled.

The evacuator pump is hooked up to both the low- and high-pressure lines and turned on for 45 minutes. This will remove all air and moisture from the system before being filled with 134a refrigerant.

With the system evacuated, it was then charged with 20 oz. 134a refrigerant, and every fitting and seal throughout the system was checked for leaks. The leak detector is capable of finding a leak as little as half an ounce of seepage per year. Classic Auto Air recommends that this step be done at a certified A/C repair center.

Before starting the engine, the compressor is turned over by hand 15 to 20 times. This circulates any oil and liquid Freon that may have accumulated on top of the pistons preventing damage to the reed valves in the compressor.

With the engine running the pressure on the high side will typically be between 150 to 175 lbs, depending upon on ambient temperature, and the low side will be between 5 to 22 lbs depending upon rpms.

Even with 85-plus temperatures outside, the Classic Auto Air system easily cooled the air to a chilly 35.4 degrees.

Good Seal

A great way to prevent any leaks and the headaches that go with them is make sure all the hose fittings are connected securely. All the fittings should be cleaned off with a scrub pad to get rid of any corrosion and rough spots. When connecting the fitting, a drop of oil should to be placed on all ends that make contact with each other. Performing these simple steps should create a leak free fitting.

Classic Auto Air made the condenser more efficient by redesigning the inside of the tubes. The stock condenser is a serpentine type with three rounded circuits. Classic Auto Air’s is also a serpentine type, but has six square circuits. This gives the condenser additional flow and cooling surfaces, thus making the condenser more efficient.


(888) 251-5684


Find Articles

Please select a field.







Put your passion into gear

From Customs, Chevys, Fords to the Classics, these magazines provide the latest cutting edge information to fuel your passion.


Required Information