When I start my 99 Deville, Ive been getting the "Ac Low Refrigerant" message on the DID all throughout the winter. Last year I did recharge the AC with an over the counter 134a refrigerant and eveything worked perfectly all throughout the summer. Obviously there is a leak somewhere. Now that summer is here again, I expected to have to perform the same procedure to have AC for the summer....not an issue. However, when I just tested the pressure, it read a tad over 45lbs. I expected it to be much less since there is apparently a leak. Why is the pressure where it should be if there is a leak and the system is detecting a lack of refrigerant? Should I simply expell the existing pressure down to some level (25lbs?) and then refill with a new charge of 134a until the pressure is back up around 45lbs again? I am aware that the proper in shop procedure would be to recreate a vaccuum an refil, but that of course would cost $$$$ since there is an apparent leak. Easier to fix for the year for a $30 can of refrigerent which is the route I would prefer to take.
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Why is the pressure where it should be if there is a leak
and the system is detecting a lack of refrigerant?
this is exactly why we say those single-gauge dispensing tanks are worse than useless -
and should NOT be sold over-the-counter -
don't take this the wrong way - but -
people who have no clue about AC systems -
become an expert - because "I did it last year - and it worked " -
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to answer your question -
you are looking at "static" pressure - not "working" pressure -
HUH?
when the AC system is OFF -
the high side and low side equalize -
that is STATIC PRESSURE -
typically - something above 70psi -
in a properly working system -
WORKING PRESSURES are a direct result
of ambient temperature and relative humidity -
example -
assuming 80* - 60% humidity -
temp set to 60* -
center vents selected -
blower on a medium speed -
a "perfect" working system system -
LOW pressure around 27 to 30 psi -
HIGH pressure around 175 to 200 psi -
center duct discharge air temp 39* to 42* -
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