Motor Vehicle Maintenance & Repair For reference I'm working on a 1986 Corvette at about 5,000 feet above sea level (I'm in Colorado). The outside temperature is about 80 degrees, and humidity is relatively low. The old R12 system had supposedly sprung a leak and the system had emptied, so I decided to convert it over to R-134. I flushed the evaporator, condenser, and all of the hoses separately, and installed a new compressor and orifice tube that came with the conversion kit I ordered. I also replaced a couple of the O-rings that were warped on the hoses. I now have everything hooked back up with the new R-134 valves on and a new accumulator in place, and am in the process of pulling a vacuum on the system before I recharge it. The vacuum only gets down to about -21 in/Hg, and won't go any further even though I let it run for at least 2 hours. The thing is, when I close the valves on the gauge the vacuum will hold in the system at that point when I let it sit for an hour and a half, which leads me to believe there aren't any major leaks in the system.

What are some possible reasons the vacuum wouldn't pull close to -30 in/HG like it should, and is absolutely necessary the vacuum gets this low to remove all the moisture? I don't know the devices used for this job, but due to the negative sign, the pressure seems to be relative, i.e. difference to ambient pressure. (When the device is disconnected and doesn't run, the gauge should show a pressure of zero, too) The absolute air pressure at altitude is shown in this plot: (Sorry for the odd values, but I'm used to SI units...) 30inHg is the absolute air pressure at sealevel at standard conditions. At your altitude, the absolute pressure is 25inHg. (Sanity check: Denver Airport (1656m) currently has 832hPa, which fits really good into the curve.) So you can't pull 30inHg, since then you would have a negative amount of gas molecules inside the system. The highest value you can get is 25inHg. You get 21inHg which corresponds to an altitude of about 11,000ft, so this can't be explained by you being at not exactly 5,000ft.

Since the system holds the vacuum, I'd say there's a problem with the device. Either the pump itself or the pipes between pump and valve has a small leak. delta ac unitsThe pump may be defect, or the oil also used as sealant is low, old or contaminated. best mini split air conditioning units(Though it looks and sometimes smells like motor oil, it isn't, and using the wrong oil can heavily affect the performance)whole house air conditioning units Creating a vacuum is not only done to remove water (seriously, how much water could be in there, plus there's a dry cartridge), it's more because it's important to have no other gases except the R-134 inside system. From that point of view, if you can't create a good vacuum, it may be possible to flush the system by adding a little R-134 and removing it again a few times.

(I really wonder why the pressure is measured relative to ambient pressure, since this leads to exactly the problem occurring here, too: Not knowing what max. value should be achieved at your location...) Edit: Since people seems to have interest in this graph, here's the formula you can use for excel etc.: Pressure = 1013hPa * exp (- altitude / 8400m) 1013hPa is the normalized air pressure at sea level in hecto-pascal. You can replace it by 760 Torr, 1.013bar, 14.7psi, 29.9inHg or whatever the pressure is in your favorite unit. 8400m is a constant in meters, you can replace it by 27559ft or whatever to match your unit of altitude. Probably a small leak at a hose fitting or something similar. I think the easiest way to check would be to fill with nitrogen and check for leaks with soapy water sprayed on all joints and connections.As I noted in my Hydronic Heating post, adding central A/C to an existing house that does not have a forced-air furnace can be a nightmare.

Running duct work after the fact is expensive and cumbersome and moreover cuts into closet space or other living space. In most cases, it simply is impossible.What is an air conditioner vacuum pump? An air conditioner vacuum pump is a pump used to remove moisture from refrigerant lines. Moisture enters an air conditioner during installation and must be removed before the air conditioner is used. If the lines are not vacuumed, the air conditioner can not work efficiently. What tools are needed to clean an air conditioner? How can an air conditioner drain be unclogged? What tools are needed to clean an air conditioner unit? When moisture enters an air conditioner's refrigerant lines, it can combine with the refrigerant and begin to freeze, potentially blocking the lines. Moisture in the lines can also corrode metal. If water mixes with the oil in an air conditioner's refrigerant, a condition known as sludging occurs. Sludging decreases the ability of the oil to lubricate parts and can result in the air conditioner breaking down.

A condensate drain pump is used to transport water from a heating or cooling system, such as an air conditioner or boiler furnace, that creates condensatio... An HVAC gas pack is a heating and cooling system with the heat pump and the air conditioner housed together in a single unit. HVAC gas packs use propane, n... What is a heat pump air conditioner? A heat pump is essentially a special type of air conditioner that is reversible. In a normal air conditioner, coolant absorbs heat in an indoor evaporator ... How much does it cost to replace a heat pump/air conditioner compressor? RepairPal estimates the cost of replacing an air conditioner or heat pump compressor to be between approximately $750 to a bit over $1,000, as of 2015. What are some advantages of a Billy Goat lawn vacuum? How does a fireplace insert improve fuel efficiency? What are some typical costs for AC replacement? What type of reviews do Ducane furnaces receive? Where can you purchase replacement HEPA air filters?