Rebuilding a ’66 Mustang’s A/C System

Summertime is the best time to drive your classic car. But it’s also the hottest, most uncomfortable time of year in many parts of the U.S. A cool July or August sunny morning cruise can quickly turn into a sweltering, sweaty afternoon in a vinyl-clad classic-car interior, and that isn’t fun for anyone — especially not for your significant other, kids or grandkids. If you’re trying to make the classic-car experience fun, you need to control that heat.

A bunch of original ’50s, ’60s and ’70s cars came with air conditioning from new, but chances are that original system isn’t functioning well — or at all. That’s where Classic Auto Air can help. They make kits to install R134a-based modern a/c systems into classic cars — and they also offer, through Original Air Group, conversion kits that can update your original a/c system with R134a refrigerant, all-new hoses and lines, and all the components you need to make it work like new — without changing the look of the control unit inside the interior.

ACC’s 1966 Mustang was an a/c car from new, but when we got it, the compressor was missing. So we ordered Original Air’s Stage 2 Performance Upgrade Kit for ’66 Mustangs, which included a new rotary compressor and clutch assembly, mounting brackets, all the hoses and fittings required, a high-performance condenser, and a new filter/dryer. It’s an affordable, better alternative to replacing original components one by one, and it makes swapping from hard-to-find R12 refrigerant a breeze. Here’s how we did it.

What You’ll Need

Original Air Group Parts List (www.originalair.com)

• 22-102 Stage 2 Performance Upgrade Kit, 1966 Mustang, $699.99
• Other Parts and tools
• Used a/c lower mount bracket for 1965–66 Mustang, $50
• A/C belt, $15

Time spent: Four hours
Difficulty: 2/5

1. An air-conditioning system may seem complex, but it’s actually pretty simple. The system uses a compressor, condenser, dryer, expansion valve and evaporator. Refrigerant (R134a) is pumped by the compressor through the lines of the system, making its way to the condenser ahead of the radiator. It cools from a gas to liquid form here, passes through the dryer, and then moves to the expansion valve. As refrigerant passes through the valve and into the evaporator inside the car, it’s rapidly cooled, and the cool air blows into the car via a fan, directly onto your otherwise overheated passengers.

1. 
   ACC’s Mustang was a factory a/c car from new, but like a lot of classics on the road today, its original a/c was inoperative and missing a few parts. Getting a system like this back on line might seem daunting, but Original Air Group makes it easy — especially if your unit still blows lukewarm air, as ours did.
2. 
   Original Air’s Stage 2 kit includes everything you need to make an original a/c system function better than it did when new. The parts include a new rotary compressor, a special adapter bracket for that compressor, a liquid hose, liquid line, a 90-degree fitting, discharge and suction hoses, a new condenser and dryer, an idler spacer, expansion valve, firewall grommet, and assorted O-rings, lubricants and decals.
3. 
   With the battery disconnected, the first step is to evacuate the system of any remaining R12, which should be done at a licensed a/c shop. As our compressor was missing and our system open to the atmosphere, we skipped this step. From there, we loosened the drive belts and pulled the cooling fan. On our Mustang, the fan is held to the water pump with four 7/16-inch bolts. If the original compressor was still fitted, this would be the time to remove it as well.
4. 
   With the fan and pulley out of the way, we started working on removing the factory dogleg compressor bracket, which isn’t used with the new, smaller rotary compressor. It’s held in place with two bolts, both of which pass into the water pump.
5. 
   The dogleg bracket sat between the a/c idler pulley and the water pump. Original Air supplies a spacer that goes in this location, which keeps the idler pulley aligned correctly.
6. 
   The factory condenser and dryer also needed to be removed, which required some front-end disassembly. Original Air suggests removing the grille for this task, but we found we could do the whole job by just removing the hood-latch assembly. Hood-latch alignment is adjustable, so we made sure to mark where everything was prior to disassembly.
7. 
   Next up were the factory horns, both of which were in the way. Note the overspray on the original condenser — it had probably never been out of the car.
8. 
   The factory discharge hose on the condenser was next, as it won’t be reused. R134a refrigerant is not compatible with the traditional rubber seals and hoses used with R12, so they all need to be replaced when converting to the new refrigerant.
9. 
   The original liquid line also needed to be disconnected from the dryer — it passes through the firewall down low on the driver’s side of the car. The kit supplies all new lines for this, too.
10. 
    The radiator mounted to studs that are mounted to the original condenser, so the radiator needed to be loosened and set aside to get the condenser out of the car. If your car still has a fan shroud, it’ll need to be removed first. Ours was long gone.
11. 
    With the radiator disconnected from the original condenser, we lifted the condenser and dryer assembly out of the car.
12. 
    1. The original brackets that held the OE condenser in the car need to be transferred over to the new unit, but placement is straightforward, as the new unit has marks that show where they go. We used 5/16-inch hex-head self-tapping screws. We also hooked up the new dryer to the condenser and tightened the fitting before putting the
    assembly in the car.
13. 
    Leaving all mounting hardware loose helps in assembly, as some brackets may need to be removed for clearance and then reinstalled once the condenser is in the car. Installation is as simple as removal — being careful not to damage the fins of the new condenser.
14. 
    The radiator is next, followed by the hood-latch assembly — but we left the horns off, as they block access to the discharge-hose fitting. Note how the Original Air unit blends in, looking like a stock piece.
15. 
    The original a/c lines were next to go, including their mounting brackets. These lines pass through a rubber grommet in the firewall, which is fastened to the car with two 5/16-inch bolts. With the grommet bracket unbolted, both lines could pass through easily.
16. 
    To access the a/c lines inside the car, we unbolted and removed the under-dash a/c evaporator and fan unit and set it on our workbench. With the firewall grommet removed, the lines and unit came out as one piece, after unplugging its power and ground wires.
17. 
    With the hoses removed from the unit, the next step was to remove the original expansion valve at the evaporator inlet fitting. A couple of big adjustable wrenches worked here, but it’s important to be careful not to bend or kink the hard lines mounted to the evaporator assembly. The original sensing bulb is part of this assembly, and it needs to be removed, too. You’ll find it under a few layers of cork tape.
18. 
    After cleaning as much of the original cork-tape residue as possible from the suction tube, we then installed the new expansion valve and routed its new sensing bulb to the factory location on the suction tube.
19. 
    The Original Air system comes with new cork tape, which covers over the new sensing bulb. The trick here is to make sure there are no air pockets between the sensing bulb and the tube. We then installed both the suction and liquid lines to the under-dash unit before reinstalling it in the car and routing them back through the firewall in the stock location.
20. 
    The only factory bracket we needed to mount the new compressor just happened to be the one we were missing, but we were able to source one locally from a Mustang shop. The bracket bolts to the face of the cylinder head and supports the original compressor from below. Original Air’s custom bracket, which comes with the kit, bolted in place on top of that OE bracket. The new rotary compressor then bolted in place on top of the new bracket.
21. 
    The new compressor mounts to the bracket with the line fittings pointed to the driver’s side of the car. The bracket’s bolts are slotted, so the compressor could be moved forward or aft to achieve proper alignment with the crank and idler pulleys. Then, once we were satisfied with the alignment, we tightened everything down. The factory trigger wire controls the new compressor, just as it would have the OE unit.
22. 
    1. With all the hoses routed, we installed them, one by one, making sure to oil each set of threads and only tighten slightly past hand-tight. All the hoses come from Original Air plugged off, as any contamination will hurt the system and void its warranty. These hoses
    feature different fitting sizes, which makes installation simple.
23. 
    After reinstalling the horns, the water pump pulley, cooling fan, and retightening the alternator and power-steering belts, we measured for a new a/c belt using a piece of string, and then proceeded to our local a/c shop to have the system charged with a fresh shot of R134a. Summer may be a few months away, but now our Mustang is once again ready for the warm days to come.