After a number of other jobs on the Scenic it was time to tackle the A/C system. Out came the Ariazone a few weekends ago to check for any system pressure, the A/C had never worked since buying the car so I was expecting the worst, busted condenser or cracked joint.
Drawing a deep vacuum on the A/C system showed no sign of leaks even after several days. I bought a bottle of EZ Chill to refill the system - £24.99 + £10 bottle deposit. Despite the system seeming intact there was a problem with it. After filling with just a small amount of refrigerant the compressor cut in (and out) but there was no cooling effect from the vents, this didn't surprise me because there wasn't enough refrigerant for the system to operate correctly. I decided that the system must have a blockage that was allowing a small amount of charge to build up enough pressure to trigger the pressure switch. My suspicions fell on a blocked Orifice tube.
The High/Low pressure pipe containing the Orifice tube was cut open using a mini pipe cutter. The Orifice tube didn't look that dirty. So the decision was made to remove the compressor, clean it up, drain the oil and refill it with 150ml Polyol Ester oil with UV dye. The accumulator was drained and the rest of the system flushed.
Here's the repair piece I bought from the US, it cost just £15 inc delivery. Renaults' solution is to buy a complete pipe. No doubt this would be expensive because the pipe is several feet long and goes from metal to rubber to metal again. Also fitting it requires the removal or bending of the heat shields in the engine bay.
After deep vacuuming the system for an hour and checking for leaks, the system was charged with the correct amount of refrigerant with the engine running. The cut in and cut of the compressor varied the pressure on the low side of the system from 27 to 43 psi, there's no high pressure service port on the Scenic. An infrared thermometer showed a post condenser/ pre Orifice tube reading of 39C with an ambient air temperature of 12C.
So here's the reading post Orifice tube. The temperature difference is 35C. Frost is beginning to form on the pipe work and accumulator. The compressor cycles on and off OK.
Before tuning on the A/C the reading was 34C, in a closed car on a hot sunny day. After 5 minutes it's reading 3C. So even though it's a uncalibrated device that's still an impressive difference, needless to say the air feels very cold.
