Yes, tire pressure read less when cold. In the vicinity of this temperature and pressure, air closely follows perfect gas behavior. In other words, P1 x V1/T1 = P2 x V2/T2 Where P1, V1. and T1 are pressure, volume, and temperature at initial conditions and P2, V2, and T2 are pressure, vloume, and tmeoerature at some other condition. IMPORTANT: Temperatures must be in absolute degrees, ie, measured from absolute zero. Absolute zero for celsus is -273 C and for Farenheit, it is -460 F. Over a working range of 30 to 50 psi, automotive tires do not change volume by a significent amount. We have the following relationship: P1 V1/T = P2 V2/T2 For our tire problem, the volumes effectively cancel leaving: P2 / P1 = T2 / T1 Solving for temperature change given the pressure change: Shuffling the preceding equation gives: T2 = (P2 / P1) T1 For example, assuming that you tire was 60F (520 R) when cold, and given that the 2 pressures were 33 and 35 psi, we have T2 = (35/33) 520 R = 1.0606 x 520 = 551.5 R or 91.5 F [ add 460 to deg F to get absolute temperature.] [ add 263 to Deg C to get absolute Temperature on the celsus scale.] As you can see, pressure does vary with its temperature. In summer, I assume that the cold temperature is 60 to 70 F and inflate to the standard recommended pressure. When the tire is hot, the pressure will be higher. Knowing how the pressure changes with temperature, we can expect the pressure to fall in cold weather. The pressure change from 60 F to 20 F is 0.923 P1. A tire inflated to 33 psi at 60 F would read 30.5 at 20 F So, should you inflate to full presure in winter? Maybe. It all depends. If you expect the tire to go up to 100 F in operation. then inflate a bit on the low side. However, it has been my experience that properly inflated tires do not gain a lot of temperature in winter. At 30 F, I inflate my tires to near the recoomended pressure ( That's the pressure on the door sticker, not the max. pressure on the sidewall of the tire. The max. pressure on the sidewall of the tire is not its working pressure, but is the max pressure the tire should ever see. Some tire shops will take the tire up to its maximum pressure when mounting a tire and as soon as it has seated on the rim, the pressure should be reduced. When the tire has been pressurized beyond the sidewall marking, it can be damaged and sometimes this damage is not apparent, but may show about 6000 to 8000 miles later. Broken or stretched belts may show as a worn out center portion of the tread. Often, the tire shows unbalance at highway speed and the tire shop will not be able to balance this out becasue the tire changes shape at speed. Its a dangerous tire and should be discarded.)

Still no answer after 4 hrs troubleshooting today. Checked Orifice for blockage as recommended but clear and checked to make sure in correct way. Checked all supply and return duct again. Ran 2 vacuums. Followed liquid line throughout attic, except for about 6 ft down wall cannot check, and no crimps or change in temps. Blower motor is only 1 speed and checked amps, ok. I can hear freon flowing thru liquid line and makes a type of swooshing sound but cannot find any type of restriction or change in temp. Temp is holding about 90 degrees on both liquid and suction line. The compressor seems to take an abnormally amt of time to kick on. I know there is a bit of a delay when power is shut off and then on, but this compressor takes about 6-7 minutes. I called supply house and asked about this and could it be adjusted, and they said delay is controlled by thermostat. I think he must've mis-understood my question. I know the guages would indicate otherwise, but could the compressor be bad or the condensor be restricted even though brand new. I am about out of options. My next option is to re-run a new liquid line-set but my gut tells me that is not the problem. Let me know if you have any other ideas, and I will keep everyone updated with this mystery unit.

I don't understand you state the liquid line is 30 to 35 degrees above at the condenser, going into condenser is normal (hot gas right?) yet 3/4 through it turns cool. Does it warm back up then as you state somewhere in the condenser before leaving?

Please forgive my haste in answering and not trying to be too wordy. You're correct, under normal conditions, if there is no air flow through the evaporator, it will begin to ice up. I guess my focus is on the impression the unit may be overcharged. Once the works are hosed up, I didn't think it would do much good to discuss the proper operations of the unit. I am in favor of the pump-down method mentioned however, not all residential units have the valves to allow you to do that. If enough air is not moving through the coil, there will be a drop in the pressure and there will be a tendency to overcharge. This will inhibit the diagnosis for this particular unit...i.e overcharged or undercharged. As you know, as you add refrigerant to a system it reaches a peak cooling plateu when properly charged. As more refrigerant is added, cooling starts to drop (temperature rise) since saturation and evaporation appear later in the coil and the temperature rises. Liquid refrigerant can begin to enter the compressor and migrate into the oil and can also begin to enter the suction side of the compressor. If the compressor attempts to compress the liquid (which it can't) the breaker will trip or, the compressor will go out on overload due to excessive amperage draw...if you're lucky, before it does much damage to the compressor or valves. The rising oil (from overcharge) or splashing (due to undercharge) can enter the intake also, creating the same conditions as liquid refrigerant. Perhaps one can be lucky and the condition that is caused by this situation is less damaging (to some extent) but will cause the evap. pressures to rise...a reed valve not completely closing due to liquid caught between it and the seat. If the reed valves are not damaged, they are weakened. Yes, the oil does eventually return to the compressor. However, in this case (grossly overcharged), if it is continually being pumped through the system, it reduces the inside diameter of the tubing and, at the same time inhibits the tranfer of heat and there is still the chance of liquid refrigerant or oil entering the compressor. At this point, to assure a proper diagnosis, this particular unit must be done by the book. I'm not an extremist so, I don't want to say this unit needs a new compressor (although it very well may). I also don't want to say it is exteremly overcharged. Before I would condemn it, I would make sure BOTH coils are cleaned. I would connect my ammeter to the common on the compressor. I would connect my high and low side guages. I would connect thermometers to the high and low side lines. I would measure the ambient temperature. Using the manufacturers chart for that unit, I would determine what the pressures should be. (so far, we're talking 5 minutes work unless coils, filters or fans need cleaning). I'd then start my diagnosis from there as to whether the unit is over charged, under charged or need replacing. Anyone who cares to know how I would further diagnose the unit, please feel free to send me an email.