Over time, our dash air does not cool.
Initially, we replaced a hose, filter/dryer and
of course evacuated and recharged several times at different shops.
We also put in green dye and looked for leaks
at night with a black light. That's how we found hose fitting leak.
Recently we have added refrigerant our selves
and found a satisfactory solution for us.
When we get into warm weather and if the dash
air is not cooling,
We add cans of R134a (Wal Mart about $9 can).
Cans are available with 134a and dye.
We have done this couple times a year over the
last few years.
Some years we have not needed dash air, like
when we spent the summer in Alaska, so no recharge needed.
The most we have added at one time is 3 cans. We try to add cans only when it is hot outside.
We heat a pot of water, put in on top of the
engine, run engine about 9,000 RPM, heater fan on high. Keep R134a can upright in hot water charging
through the vacuum port.
We have a digital thermometer on the dash with
outdoor lead permanently fed down to the evaporator area under the
dash. A wireless thermometer would also work fine
We watch temperature while adding cans and when
it gets down to about 45, we stop adding cans.When it is real hot out and we think the system
is not cooling enough,knowing the evaporator area temperature gives us the knowledge that
the system is working just fine if we see temps in the 40 to 45
range, sometimes down to 35.
Our system has never leaked out completely.There is always enough pressure in the system
to keep the low pressure switch closed (which allows the compressor
to run).The pressure, even though too low for cooling,
will keep outside air from infiltrating into system.