I believe Mr. David Teitelbaum is correct on this one. Air condition and refrigeration systems must be properly done with good equipment, especially, the evacuating pump for the COMPLETE evacuation of atmospheric air in a system. The cheaper or a weaker pump will not do it properly. On the same breath, there are "hidden and long range damages" that can occur from not evacuating the system properly. If I am not mistaking and if I do remember the facts that I was taught, moisture which is actually atmosphere air composed of different gases and when it is mixed with freon in the closed system, it will turn in to hydrochloric acid and it will corrode your system from inside out. This will lead to premature failure of the hoses and all the components, especially the aluminum units such as your evaporator and condenser. So, a decent evacuating pump if a must. Every bit of minuscule of air must be removed! Also as a rule of thumb, when a system is opened, as in a rupture, or a component failure and when replacing the part or parts, the RECEIVER DRIER or the DESICCANT BAG MUST BE CHANGED! Then immediately evacuate the system with a REAL or an able commercial vacuum pump for at least a minimum of 20 minutes and the longer evacuating, the better. One hour is best for an average car. Afterwards, turn off the pump and do check your gauges to make sure the system is sealed and holding vacuum, with no leaks. With the pumps off and all valves shut, the gauges MUST be holding and reading a complete vacuum with no movement in the gauges at all! Only then, you can fill the system with the required type and the proper amount of freon. If the gauges shows even a hair line of movement, it is an indication of a leak, DO NOT FILL, for it is waste of the freon. You MUST check the system again, to FIND and to CORRECT the leak or leaks in the system BEFORE FILLING with the CORRECT AMOUNT, by USING the gauges and the PROPER STEPS to introduce the freon into the system, with no ands, ifs and buts about it. Do this correctly and you should have NO problems with your A/C system. BTW, With some present cars and older cars, they have a "sight glass" which is dedicated to that car's system. This sight glass is usually the best indicator, for it shows "sight on seen" the amount of freon in the system when the A/C is turned on. Bubbles means the system is low, clear means fully or over charged or empty. The DeLorean does not have a sight glass, so you have to depend on the gauges, unless, you add one onto the system for your own conveniences. Kayo Ong #5508 Lic 9D NY [Non-text portions of this message have been removed]