Things technicians do to sabotage your aircon

By Technicians:

1)     Topping up of refrigerant

The refrigerant (commonly known as FREON) is not a magic substance, it is not cold by itself. Scientists around the 
world are busy trying to find that magic substance and we’re not too sure if anyone’s found that. What we are very sure 
is that refrigerant used in your air conditioner is definitely not that magic substance. Do not be mistaken that if you add 
more FREON into your system, your air conditioner will be cooler. In fact, the opposite will be the result.

The fundamental of air conditioning is the use of a compressor to compress and decompress the FREON. It is through 
the manipulation of the gas pressure that created the temperature difference; thus it is very important for an air 
conditioning technician to be well versed with the enthalpy chart of different types of refrigerant before meddling with the 

If too much liquefied gas is produced by over charging your system, this is a condition called “evaporator flooding”. 
Meaning, the entire blower is filled with liquefied Freon, thus, leaving no more room for evaporation to take place. This 
explains why adding more gas into the system WILL NOT make your system any cooler, but rather it will encourage 
liquid FREON return which (if exceeds your manufacturer’s specification for the critical amount of gas to go into your 
system), WILL cause permanent damage to your compressor due to 2 reasons. First, the liquefied Freon returning to 
the compressor will dilute and damage the compressor oil, causing premature wear and tear. Secondly, as liquid cannot 
be compressed, sending liquid directly into the compressor will cause serious damage to your compressor.

2)     Using refrigerant gas to purge/flush the fan coil (normally to the condenser)

Do not use refrigerant to blow at the condensing coil in an attempt to purge dust off the surface. Not only is it illegal (for 
causing ozone depletion), it also a very wrong thing to do as the gas itself will cause the aluminum fin to corrode.

3)     Full dismantling of fan coil for chemical cleaning without ensuring total removal of water and water 

When a fan coil is removed for chemical cleaning and subsequently washed with large amount of water, certainly some 
water will enter the copper pipe. This water moisture cannot be taken likely because their presence will damage the 
compressor oil. When the compressor oil is damaged, it results in high friction which produces lots of heat and abrasion. 
It may cause high running amps which causes premature breakdown of electrical relays and starting capacitors.

When a compressor overheats, it will trigger an overload relay to shut down the compressor. The compressor will only 
spring back into action after it has cooled down, it can take 1-2 hours for that to happen.

4)     Full dismantling of fan coil for chemical cleaning without ensuring joints are not damaged resulting in 
future gas leak

The compressor uses a large part of the returning suction gas to cool the compressor down. But when a system runs 
out of gas, there’s little cold returning gas to cool the compressor down. This will certainly overheat the compressor.

When a compressor overheats, it will trigger an overload relay to shut down the compressor. The compressor will only 
spring back into action after it has cooled down, it can take 1-2 hours for that to happen.

5)     Removing of overload relay in order to force run a compressor

When a compressor overheats, it will trigger an overload relay to shut down the compressor. The end result is that the 
air conditioner no longer produces cold air. If at this moment, a technician bypass this overload relay in order to force-
run the compressor, the compressor will certainly overheat.

When the temperature of the compressor rise above 150’C, the compressor oil will fully disintegrate. Meaning, this will 
cause enormous wear and tear to the compressor, and causing the dryer filters to be choked.

If the temperature of the compressor further exceeds 250’C, the R22 gas will break down and produce acid in the 
presence of water moisture. This will be the worst; the acid will start to corrode the copper pipes, resulting in leakage 
at places least likely to occur; at the connecting pipes, which possible is tucked away from sight; above the false ceiling, 
inside walls or behind cabinets. This will be a home owner’s worst nightmare.

6)     Taking suction pressure as indicator for appropriate gas level

Please Do Not meddle with the gas unnecessarily Unless there is a gas leak which is rare, please do not top up more 
than necessary gas. Never attempt to read the gas pressure blindly. The gas pressure varies according to different heat 
load and condition of the heat exchangers. When the fan coil is very dirty, the pressure will be low because liquified 
freon are not fully evaporated.

Newer air conditioners called “inverters” regulate their compressor rotational speed and causes the pressure to vary as 

If during installation certain part of the connecting pipe is kinked/dented, it will show an inaccurate pressure reading as 
well. Gas pressure cannot be analyzed simply by plugging in a meter at the suction pipe. Technician must be well versed 
with the saturation table of different types of gas. Head and suction pressure must be considered in relation to the 
running ampere and temperature of the indoor and outdoor environment.

5)   Using hot steam cleaner /hot water to disinfect the air conditioner.

Undeniable, hot steam / water kills germs. BUT do you know hot steam/water measuring 100’C wiil risk damaging your thermistor? Worst, mold do not “die” unless the temperature is raised above 140’C. Steam which is 100’C, cannot “kill” mold but rather stress them, causing them to produce mycotoxin, you will be worst off. If you google and read up on mold, you’ll know what i’m saying is true.

Thermistor is a temperature sensing device placed at the fan coil to detect the temperature of the fan coil and/or air. It is 
a variable resistance component that has a working temperature ranging from some -50’C to 125’C (may vary from 
different manufacturer).

The temperature your thermistor in your air conditioner is usually operating between 10’C to 28’C. I would say, a stress free environment for the thermistor to last you a long time. I don’t think pushing it to 100’C is a good idea.

Thus, if you really want to use a hot steam cleaner, do remember to remove the thermistor first!

Also please bear in mind that while hot steam kills bacteria, it will not remove dust that chokes your fan coil. If there is rubbish in your room, you will need to throw them out, don’t you? Do you use hot steam to disinfect the rubbish?

When your fan coil is choked, the only proven way is to use alkaline based chemical (so that it doesn’t corrode the fan 
coil) and flush the dirt out using very high pressurised water.

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