When we are working with HC12a/134+® we can use any of the above lubricants or oil. The only problem with going back to natural mineral oil is the ready availability and cheap price of R134a. If it is not your vehicle and it gets low, some "shadetree" mechanic is going to shoot in a can of 134 and create a mess. Since most manufacturers use PAG (the worst), I try to flush all my systems and use ESTER because it is not as bad as PAG with moisture and it lubricates much better. HC12a/134+ tends to mix well with this lubricant, it pulls all the lubricant off the walls (as mentioned above) and brings it back to the compressor where it was meant to be. Also, oil based HC12a/134+ neutralizes any caustic action in the system, therefore a system charged with HC12a/134+ should never become contaminated with acid buildup. In all of my vehicles, I use HC12a/134+ and mineral oil, but they are mine and I know I will never use 134 again.

When the air condition quits cooling we know something is wrong. We must find out why it quit and what is required to repair it. First we turn the compressor clutch hub and crankshaft. If it is frozen up or has tight spots we know we are going to replace the compressor, drier/accumulator, orifice, and flush. If the crankshaft turns without tight spots, we need to check pressures. If it is low, we have a leak, if it is out, we have an open leak. We need to find out the last time refrigerant was added and how long it lasted. This gives us an idea of what size leak we are looking for. If the leak is not fast enough to look for, add oil and dye, this will aid in finding the leak later. If the leak is large enough to require frequent charging (monthly or less), use shop air to pump up the system to 100-150 psi. (Remember when using HC refrigerant we are not concerned with air or traces of moisture.) You should be able to find your leak with soap bubbles.
Two items you need to add to your toolbox are:

• A homemade hose for your manifold gauges (take an old hose from the gauges, cut it off and put a tire valve in the end so air pressure can be applied through the gauges)
• Jumper wires to go directly from battery to compressor clutch coil (go to a wrecking yard and cut off terminals to plug on different coils)

Now charging, regardless of the repairs we are doing, we need to look at the orifice tube. It will show us the condition of the rest of the system. If it is OK proceed. If it is stopped up, the high side needs flushing. If you have an expansion valve, you should be able to blow through it from the high side. If it is stopped up you will need to clean or replace it and also replace the drier and flush line between the drier and expansion valve. Most likely the desicant bag has broken down in the drier and stopped up the expansion valve.

We now have the system repaired, clean, and dried. Now we need to think about oiling the system. The number one problem in compressor failure is lubrication (not enough oil or contaminated oil). Now we have the chance to make this compressor last ten years or more. We are using HC12a/134+, which will blend with any refrigerant oil and keep it moving through the compressor. A well oiled compressor will last many years. In experiments I find natural mineral oil to be the best, but I use a lot of ESTER oil also. I do not use any PAG oil. Again with HC I use a little more oil than recommended with synthetic refrigerants. In a small car with an expansion valve and drier, I use 12 oz. In a larger car, pickup, or van, I use 14 oz. In a vehicle with dual air and orifice tube and accumulator, I use 16 oz. I am oiling the system, not trying to make a certain percentage blend.

How to Install Oil If you are installing a new compressor, put oil in the low side while turning the crankshaft. Put 6 ounces in the compressor and install compressor. Hook up gauge hoses to system, hook yellow hose to vacuum pump, start pump, open high side valve, low side closed, take low side hose loose at gauge manifold. You should have suction at the end of the blue hose. Stick it in measured amount of oil and suck it into the system. Put hose back on gauge set and pull a vacuum on system.

Now you are ready to install HC12a/134+. Open valve on tank, purge yellow hose, SLOWLY charge as a liquid on low side until you get to 50psi. This engages all switches. Start vehicle, set on max, high fan, and allow clutch to cycle as you add refrigerant, low side, liquid, until clutch quits cycling. Increase RPM to 1500 and add more until clutch stops cycling, charge low side 25-35psi according to ambient temps. This should put your high side around 200psi.

Keep records and you will find you can offer your customers 2 year Warranties on compressors. You will have no competition from the synthetic refrigerant crowd. After performing the above work, if you have high head pressure, check the fan, not the cooling condenser. If you have good pressures and are not cooling, check blend doors, letting hot air in the evaporator housing.

Have you ever taken that big, tough Hummer out to enjoy an open country ride on a hot weekend only to have the air condition go out in the first 20 miles and then find out the compressor locked down or the compressor clutch burned out? These problems occur quite frequently, but can be avoided if we correct the high head pressures before they happen. After they happen, we must first repair the damage then deal with the pressure problem to ensure it won't happen again. If we replace the compressor with a new one and fix the head pressure problem, we warranty our new compressor for 2 years. We do this on all other vehicles, and see no reason why the Hummer should be treated differently. Your head pressure should run no higher than 250psi, and you should get about 45 degrees or less at the vents. We are working on a higher volume fan in the Hummer. We see this most on the older models, and the later models seem to do a little better at cooling. We still need to get their head pressures down. Hydro Cool, Inc., through its service division, is experimenting with many air condition problems in all types of vehicles. We have determined that better lubrication, lower pressure, and colder air is the answer to our dilemmas in mobile air condition systems.