Air Conditioning Basics

Having recently completed my air conditioning system, i thought i would layout what it takes to install your own modern air conditioning system. Air conditioning is one of those mysterious things that everyone is afraid of when in actuality its not much more complicated that the coolant system on an M10. There is a liquid that gets pumped around a sealed system and as it expands it cools and then we compress it again through the compressor, lower its temperature though the condenser and then repeat the process.

A basic air conditioning system is made up of the following components.

Evaporator (The unit that mounts in the vehicle and has your AC controls and vents)

Compressor and mounting bracket

Condenser (The radiator that mounts at the front of the car in the engine bay)

Electric push fan

Hoses and dryer

I will discuss what you need to know about each component:

EVAPORATOR

This is going to be the toughest component to track down because you cannot buy a new unit. 2002 did not come with air conditioning from factory and so you have to track down an aftermarket unit from the 70's that was installed into the cars by the dealer. You need to source a used Clady, Behr or Fridgeking evaporator / center console though the for sale forums. Any unit you get should be pressure tested and the expansion valve replaced.

This is my Behr system. The systems all look different and different people prefer the looks of different systems.

The evaporator produces a large amount of water when it operates and the evaporators have a water drain hole in the bottom. You will need to drill a hole through the top of the transmission tunnel to install a rubber drain hose so that the water doesn't flood your interior. The switches for the evaporator should be cleaned, checked for electrical function.

Remember old evaporators use flare fittings. Modern hose kits are O ring kits. You will need flare to O ring adapters that are used with flare fittings in order to convert the flare fittings to O ring fittings. #6 and #10 flare adapters.

https://nostalgicac.com/fittings-hose-kits/flare-adapters/6-flare-to-o-ring-fitting-adapter.html

https://nostalgicac.com/fittings-hose-kits/flare-adapters/10-flare-to-o-ring-fitting-adapter.html

You can also buy copper crush washers which go into the flare adapters to help with the seal if your flare ends aren't in pristine condition.

COMPRESSOR AND BRACKET

We will keep this simple. The old system compressors are much larger and heavier than modern rotary style compressors. Dont even bother with an old compressor. Buy a modern Sanden 508 compressor. You can buy genuine Sanden for $250 or a chinese knockoff for $130-$150. You will need a V belt model and these can be gotten from Ebay or http://nostalgicac.com/.

Very important. The Compressors must be filed with oil. There are different types of oil and some oils are compatible with old style freon (R12) and some are compatible with new style freon (R134a). Since R12 can no longer be obtained you might as well plan on using R134a freon which mean Pag or Ester oil.

Compressor uses 6oz of oil after you fully drain all the shipping oil from the unit.

The bracket is easy. The Clardy system came with a bracket that fits the Sanden 508 compressor but also luckily a 2002faq member is now making an excellent bracket which can be bought from hobiedave.

http://www.bmw2002faq.com/topic/82340-custom-made-ac-compressor-brackets-sold-out/?hl=hobiedave

Blunttech now also sells a Sanden 508 bracket

https://www.blunttech.com/shop/replacement-parts/climate-control/1448btkt

CONDENSER

The condenser is simply a matter of size. The bigger the better but you need to factor in how big can you fit into the nose of the 2002 and whether or not you are willing to cut the support bars to fit a larger condenser.

I used a 9"x12" on my first car and a 10"x 18" on my second car. Both fit well with no cutting. Get the biggest condenser you can fit (So probably the 10X18)

You will need to mount this to the front of the nose, there are condenser mounting straps or you can zip tie it in depending on how much drilling and modifying you want to do.

FAN

You will need an electric fan on a relay kit to blow air through the condenser. The fan should be sized appropriately to fit into the nose of the 2002.

I used a 10 inch fan which in my opinion fit perfectly. Don't forget to power the fan directly from the battery with a relay kit since it draws a lot of amps.

HOSES AND DRYER

People get scared by the plumbing of the AC system, but its actually very simple. There are standard AC hose sizes and certain sizes go between certain components.

You will use #10, #8 and #6 size hose in your install.

The #10 runs from the evaporator to the compressor. The #8 runs from the compressor to the Condenser. The #6 runs from the condenser to the dryer and then back to the evaporator.

I like to put heat shield sleeves over the lines running near the exhaust.

Ebay and http://nostalgicac.com/ sell "Hose Kits" which include the hoses, connections, safety switch and the dryer. Buy a universal kit and it should have everything you need!

The safety switch measures freon pressure levels and cutoff the system if levels get too high or too low. It gets wired in series with the AC controls and compressor.

To make your own AC lines you will need a crimper tool. I used this one and it worked great.

I also used a substance called Nyloc with all my o ring fittings. Its a type of AC sealant and you coat the O rings in it before tightening and it helps to minimize any leaks. This stuff is option but recommended.

Once everything is installed you will need to have the system charged with freon by a professional AC shop. But if everything goes to plan you will have good cold AC for under $1000.

EDIT:

If you wish to charge the system your self, you will need a proper 3 line gauge set ($35 on ebay) and a vacuum pump ($50 on ebay)

Attach the low and high pressure lines to the AC system, attach vacuum pump to yellow line and start vacuuming. Open low pressure side valve on gauge and allow pressure to drop to -30psi. Vacuum for 30 minutes to remove moisture and air from system. Close low pressure valve and remove pump. Make sure system holds negative pressure for 30 minutes to ensure no leaks. Afterwards attach a can of Freon to yellow line. Start car and turn on AC to max. Open low pressure valve and let Freon into system. Low pressure should jump up to 60 psi but then the compressor should kick on and pressure will drop down to below 20. Note that the compressor pulley always spins but only when the clutch kicks in and the center part of the pulley is spinning is Freon being pumped!

System will likely need 2.5 cans of R134a Freon (3 cans is too much). We want low pressure of about 30-35 psi and high pressure around 250 on a nice day. (Pressures vary by day time temperatures). Remember to close the low pressure valve when switching Freon cans. Also the gauges pressures sometimes take a while to settle so add the 2 cans and then rev the motor up and let the system cycle a bit before deciding if pressures are right or if more is needed.

A system with too much Freon will not cool! More is not better!