Page 245 - Foton Workshop Manual - Auman EST-M

Diagnosis - Diagnosis-fault diagnosis of electronic and electrical parts DI - 191

Air conditioning system leakage detection method IN
Caution

Leakage tests are recommended when there is a suspicion of a leakage in the air conditioning system DI
or when servicing the air conditioning system. Commonly used air-conditioning leakage detection
methods: visual leakage detection, liquid soap leakage detection, electronic leak detector and vacuum EG
leakage detection.
1. Visual leakage detection TR

If there are oil stains somewhere in the system, it may be a leakage point. Visual leakage detection is simple

and cost-effective, but there are great defects. Unless there are big leakage points as the system suddenly
AX
fractures and what leaks from the system is liquid colored media, others are hard to be positioned by the visual

leakage detection because the leakage is usually subtle, and there are many parts of the automotive air
conditioning out of sight. FR
2. Check leakage with soap solution

Liquid soap leakage detection is a simple and effective method: the parts and pipe surface covered with oil ST
stains shall be wiped up, and then smear the liquid soap on the detected position, if the joints need to be
detected, smear the liquid soap on the whole ring uniformly. Observe carefully and comprehensively, if there
BR
are bubbles, it can be judged as a leakage. The key is to control the concentration of liquid soap, and it is not

allowed to be too thin or too thick. This method is more economical, practical and applicable to the exposed
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parts which can be seen by people and occasions with refrigerant gas around. But the accuracy is poor, and it
can not check the microleakage and the parts which are not easy to be smeared with liquid soap and observed,
such as compressors, evaporators and condensers. EL
3. Electronic leak detector

Small leakage can be detected, especially where hard to reach

a. Most electronic leak detectors are provided with check gear, before use, confirm that the check is correct,

and make the indicator light and alarm bell work.

b. Adjust the instrument to the desired sensitivity range.

c. In detection, the probe shall be placed in all directions to prevent detection missed.

d. Once leakages are detected out, the probe shall be taken away immediately for fear of shortening the
service life of the instrument.
4. Vacuum leakage detection

Vacuuming is to exclude the air and moisture inside the refrigeration system, and it is an extremely important
program in the air conditioning maintenance. When the air conditioning system is being serviced or
components are replaced, the air will enter the system and the air contains a certain amount of water vapor, so

the refrigeration system shall be vacuumed. With vacuuming, the water cannot be drawn out directly from the

refrigeration system, instead, the boiling point of the water is lowered, and the water vaporizes and is drawn

out from the refrigeration system. Therefore, the longer the vacuum is, the smaller the residual moisture in the
system is. Vacuum leakage detection steps:
1. First, connect the high-pressure hose of manifold pressure gauge to the high-pressure maintenance valve of
air conditioning system, and then connect the low-pressure hose to the low-pressure maintenance valve, and
connect the intermediate pipe to the vacuum machine.

2. Open the high pressure manually maintenance valve and low pressure manually maintenance valve of

manifold pressure gauge, start the vacuum pump and observe the vacuum gauge on the low pressure gauge

until the pressure is vacuumed to -80 to -100 kPa.

DI-191