In
fact, there are countless reasons why the A/C system is not working; a low
refrigerant charge is just one of the several possibilities.
Now
having said that, understand that adding some refrigerant is an excellent
‘test’. But it should only be used as a test. That is, when diagnosing
an A/C system, it can be difficult to tell the actual cause of the failure
just by pressure gauge readings. For that reason, a simple test is to add
some refrigerant. If adding some refrigerant to the A/C system causes an
improvement in the cooling performance, you have basically verified that
the system was just low on refrigerant. To repair the system you would have
to perform a complete leak test and repair all the leaks; replace the drier
or accumulator; pull deep vacuum and then recharge the system with the full
factory specified amount of refrigerant.
Understand
that the general rule for adding refrigerant for test purposes is:
a) For A/C systems that are up to 2 pounds in total refrigerant capacity
-add 2 ounces
b) For A/C systems that hold over 2-1/2 pound of total refrigerant charge
- add 4 ounces
Why
should the added refrigerant only be for test purposes? That’s easy!
If you’re taking this test, you already know that the pressure gauge
readings will never tell you how much refrigerant is in the A/C system. The
only way to tell exactly what’s in the system is to recover, vacuum
and recharge it. So even after adding refrigerant, you really do not know
how much refrigerant is in the system. For that reason, you must then recover,
vacuum and recharge the A/C system.
However,
on the other hand, if adding some refrigerant did not improve the cooling
performance of the A/C system, adding more isn’t going to either. What
the addition of refrigerant has done is that it’s confirmed there is
another problem on the system.
Diagnosing
the problem is beyond the scope of this auto A/C service test, and we would
strongly suggest that you review the
auto
A/C help information on DVD video or the
ebooks
on Diagnosing Auto A/C Systems.
Typically,
you the diagnosis would start by confirming that all of the components of
the A/C system are functioning properly. Visual inspection of cooling fans,
fan shrouds, etc. would be a good place to start. When doing that, don’t
forget to check engine cooling performance and coolant levels because an
overheating radiator can cause poor cooling in the A/C system.
Other
possible causes could range from restrictions at the expansion valve or receiver
drier, an overcharge of refrigerant oil or cycling and temperature sensing
switches that are malfunctioning. But remember, the added refrigerant should
only ever be for test purposes only! |
This
was probably one of the best books on recharging air conditioning that I
have seen...
