Repairing a Leak in a Refrigeration System
1. Locate the Leak
Before starting any repair, you must be 100% certain of the leak's location.
- The Soapy Water Test: Apply a mixture of water and dish soap to joints and tubing. Bubbles
will reveal the leak. - UV Dye: If UV dye was previously added, use a UV light to find the glow.
- Oil Spots: Refrigerant contains oil; a "greasy" spot on a pipe is often a sign of a leak.
2. Evacuate the System
You cannot braze or seal a system that is under pressure.
- The refrigerant must be extracted using a recovery unit into a certified cylinder.
- Warning: If the unit uses R600a (Isobutane), the gas is highly flammable. Ensure maximum
ventilation.
3. Repairing the Leak
The method depends on the location and material (copper or aluminum):
- Brazing (Copper-to-Copper): The most durable solution using a torch and silver-content filler
rod. - Epoxy/Lockring (Aluminum): If the leak is in the evaporator (inside the cabinet), which is
often aluminum, it is difficult to braze. Use specialized epoxy or a mechanical "Lockring" fitting.
4. Replace the Filter Drier
Every time a cooling system is opened, the filter drier (the small copper cylinder before the capillary
tube) must be replaced to ensure no moisture enters the compressor.
5. Vacuuming (The Most Important Step)
Once sealed, all air and moisture must be removed.
- Connect a vacuum pump.
- Run it for at least 30–45 minutes until the gauge shows a deep vacuum.
- Let it sit for 15 minutes to see if the needle moves; if it does, you still have a leak.
6. Recharging the System
- Check the nameplate on the back of the fridge for the exact charge (e.g., 54 grams of R600a).
Use a precise digital scale. The performance of a domestic fridge depends on the charge being
accurate to the gram.
How to Braze Refrigeration Tubing
In refrigeration, we use brazing rather than soft soldering because the joints must withstand high
temperature fluctuations and compressor vibrations.
Tools Needed:
- Torch: MAPP gas or Oxygen/Acetylene.
- Filler Rod: Silver solder (2-15% silver) or Phosphorus-copper rods.
- Sandpaper/Emery Cloth: For cleaning.
- Heat Shield: To protect plastic parts of the fridge from the flame.
The Step-by-Step Process:
1. Preparation (Crucial!): The pipes must be perfectly clean. Use sandpaper to polish the ends until
they shine like a new coin. There must be no grease, paint, or oxidation.
2. The Joint (Swaging): One pipe should be expanded (using a swaging tool) so the other pipe can slide
about 1 cm into it. This creates a "capillary effect" that sucks the molten metal into the joint.
3. Heating: Light the torch and move the flame evenly around the joint. Do not heat the filler rod
directly; heat the copper pipe instead.
- Color Guide: The copper should turn from dark red to bright cherry red. If it turns glowing
white, it is too hot.
4. Applying the Filler Rod: Once the pipe is at the correct temperature, touch the filler rod to the joint.
If the pipe is hot enough, the rod will melt instantly and be drawn into the gap by itself.
- Tip: Pull the flame away for a second while applying the rod so you melt it with the heat of the
pipe, not the flame.
5. Inspection: Let the joint cool naturally (do not use water to cool it, as this causes cracks). A good
braze should look smooth and silvery/shiny all the way around with no gaps or lumps.
Safety Warning for Fridges:
Modern fridges often use R600a. If you apply a flame to a pipe containing gas residue, it can result
in a flash fire or explosion. Always purge the system with dry nitrogen before brazing if possible,
and work in a well-ventilated area