99 Civic EX - A/C inconsistent in blowing cold

The Facts: 99 Civic EX 5spd, 150k miles, drives real good with
minimal issues.

Lately, the A/C has not been consistent in blowing cold. Sometimes it
feels pretty good, other times it feels like it's just blowing from
the vent w/o any cooling. It seems to be blowing warm mostly at stop
and go/city driving, but that might be my imagination.

Any idea what causes this? Thanks!

 

A/C systems naturally lose roughly an ounce of refrigerant per year. You're
probably running about half-charge right now.

Go get it topped up again.

 

I'm sure you're right, but that's not what irritates me. I was having
other A/C problems late this winter (January or so). Sometimes the
blower would come on, sometimes it wouldn't. I'd spin the knob hoping
to hit a sweet spot and make it turn on. Sometimes it worked, usually
it didn't. I replaced that control unit, thinking maybe the knob pot
was bad. Anyway, that wasn't the issue.

So I took it in to the dealer. He told me the system was "over
charged" so they released some coolant. I don't recall having my
system serviced, but let it go...

So he must have taken the coolant out, and maybe that wasn't the
issue...

So... while the blower usually turns on and spins at the speed I
desire, we're just blowing warm and semi-cold now. I'll have it
looked at for more coolant to be added. Thank you.