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    Thread: DIY - Checking A/C Evap Drains and A/C Performance Testing

    1. Member
      Join Date
      Nov 27th, 2004
      Location
      Charlotte, NC
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      7,180
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      2000 VW Jetta VRT, 2000 Audi TT Quattro
      05-16-2007 01:32 PM #1
      DIY - Checking A/C Evap Drains and A/C Performance Testing
      If you notice that your air conditioning is not quite as cold as it was, or is not working at all, then before you start replacing components in the system, do these items before you spend any extra money.
      If you have not already done so, please refer to This Thread for some very good additional information about the A/C system.
      Tools Required
      -Blade Screwdriver
      -Long (about 2'), thin flexible plastic piece
      -Jack and Jackstands
      -Torque Wrench
      -Garden hose or air compressor
      i. Initial Conditions
      -The hood is open
      -The front of the vehicle is raised
      Please be careful when performing this procedure. I can't be held responsible if I have made a mistake in the following steps.
      Cleaning the Evaporator Water Drain Valve
      The evaporator is contained inside the dash and is very difficult to get to. Condensation that builds up on the evaporator will drip into the dash housing and drain through this valve. If the valve is blocked, then water will build up inside the housing and cover the evaporator.
      1. The drain valve is located behind the this firewall flap.

      2. Using a blade screwdriver, flip open the flap in the firewall.

      3. Most drain lines have a cover on the front; I removed mine to prevent any possible blockage. Insert the long plastic piece up the drain line to clear out any blockage. Be careful, as there could be up to 3 gallons of water inside the dash.

      4. After the line is clear, close the firewall flap until it is flush with the surrounding pieces.
      5. Next, use your garden hose or air compressor to blow out any debris that is lodged in the condenser. You will need to remove the front bumper skin per http://www.ottawa-vdubbing.com...10525.
      A/C Performance Testing
      Tools Required
      -Gauge Manifold Set (about $30 at your local autoparts store)
      -Thermometer (about $10)
      i. Initial Conditions
      -The hood is open
      -The outside temperature is 68-86 F.
      NOTE: When attaching the manifold lines to the high/low pressure service ports, you WILL get some refrigerant in the manifold lines. It is EXTREMELY cold when you remove the lines from the ports.
      1. With the engine off, turn the A/C off. Then start the engine.
      2. Close both high and low pressure valves on the manifold.

      3. Connect the high and low pressure lines to the service ports on the A/C system. NOTE: The high pressure port sometimes sticks closed. You may have to press down hard on the fitting to get the fitting to lock into place.
      4. Start the A/C and enable recirculation. Select the temperature to full cold and select the blower speed to the highest setting.

      5. Bring up engine speed to approx 1500 RPM. You can bring it up to about 1250 using a Vag, but I ended up cutting a piece of wood and jamming it against the seat and the gas pedal.
      6. Open all the passenger outlet vents, and insert the thermometer into the center vent.

      7. Open the Low pressure side valve on the manifold. This will read low side pressure. It should be approximately 17.4 psi.

      8. Next, CLOSE the Low pressure side valve, and then open the high pressure side valve. You do NOT want to over-range the low side gauge. The high pressure reading should be approximately 203 psi.

      9. Select the second blower speed and wait 1 minute. Then, read the temperature off the temperature gauge. It should be less then 50 F - Temp Drop.


      If the system pressures are not reasonably close, or the system does not cool sufficiently, then you will need to perform the next tests. The assumption is that the A/C system is fully charged, although the tests will give you an idea of what to repair.

      High Pressure Test
      1. Shut down the engine and turn off the A/C.
      2. Temporarily disable the coolant fans by removing the fuse show below. NOTE: This will ALSO disable the after-run coolant pump, so keep a close eye on engine temperature.

      3. Start the engine and adjust engine speed to 1500 RPM.
      4. Turn the temperature control as hot as it will go, and adjust the distribution to the footwells. Turn the blower on high and start up the A/C.

      5. Close the low side manifold valve and open the high side manifold valve. The high side pressure should spike to approx 232 psi - Hi Pressure within 30 seconds and with the compressor running.

      6. Next, turn the temperature knob to max cold. Set the blower to its lowest speed, and direct the air to the passenger vents.

      7. Then, close the high pressure side manifold valve and open the low pressure side manifold valve. Pressure should be approx 22-36 psi - Lo Pressure within 30 seconds.

      8. Reinstall the fuse you removed.

      9. Shut down the engine, and compare the pressures you got in the above steps to the table below:

      Let me know with questions as always.
      Mike
      Chapter 11 Dubs: Member #001
      http://www.chapter11dubs.com
      -----------------------

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    3. 05-16-2007 02:01 PM #2
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    4. Member RavinJetta's Avatar
      Join Date
      Mar 31st, 2002
      Location
      San Diego
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      2011 S4
      05-16-2007 02:17 PM #3
      Great DIY

    5. Member jink's Avatar
      Join Date
      Oct 7th, 2005
      Location
      FL
      Posts
      166
      Vehicles
      2002 VW GTI 12v VR6
      05-17-2007 02:45 AM #4
      Great guide, this unfortunately seems to be a pain for users with climatronic. If my A/C wasn't making a noise like the clutch on my compressor was going out, I would give this a shot. Excellent DIY.

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