How to diagnose a/c restrictions by feel
If you are diagnosing an air conditioning system and experiencing crazy readings one of the tools you can use is your touch. By simply feeling the air conditioning hoses you could pinpoint a problem.
Typically on air conditioning systems, the components on the high side are always warm or hot to the touch. On the low side, the components are usually cold or cool to the touch.
You can diagnose a restriction in either the high or low side by simply moving along the air conditioning lines and feeling for any type of temperature change. Any change in pressure will show itself as a temperature change or even Icing at the point of the restriction.
When feeling the hoses on the air conditioning system, feel the ends of the hoses where they hook up to the components. Most of the time it is not a restriction in the hose itself. It is actually restriction in one of the air conditioning components.
Feel the air conditioning compressor to see how hot it is. The air conditioning compressor should be warm to the touch but not extremely hot.
If the air conditioning compressor is very hot, you could have broken valves inside the AC compressor or a bad piston. Touch is one of the little tricks you can use to diagnose air conditioning problems. Here are a couple tips.
If you feel the receiver drier and it is cold to the touch, chances are you probably have a restriction in the receiver drier or the pickup tube.
If the suction line going to the expansion valve is cold to the touch, you probably have a defective expansion valve. Is the expansion valve itself is cold, the expansion valve is probably stuck closed.
However you diagnose the AC system, this is a very good way to pinpoint a restriction in the system. You can also use a temperature infrared heat gun if you have one in your toolbox. This will make the job a lot easier in tight spaces where you can't reach.
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