Air conditioner

If the air conditioner doesn't get cold in a 1993 Caravan, what is the
single most likely reason? Is it likely to just need to be recharged?
How much does that usually cost, and how often does it usually need to
be done?

 

Most likely, it needs a recharge. Most shops charge a base fee, plus
any refrigerant needed. If there is a leak in the system, it will have
to be repaired. Depending on where the leak is will determine the cost.

-Kirk Matheson

 

How much is the base fee likely to be, and how much is the refrigerant
likely to cost?

How would they know if there's a leak? What if it takes two weeks for
enough to leak out to disable it? Would they notice a small leak like
that?

 

I don't have a clue, and it depends on the shop. Figure on the standard
hourly rate and maybe an hour of shop time to diagnose, or at least prep
the system for diagnosis. Just a SWAG on my part.

Not much. R-134a is fairly cheap. If this were an old R-12 car, it would
be a different matter (though R-12 is cheaper than it was for a while
since demand is dropping fast).

By any of a number of different methods. A big enough leak will leave a
visible stain of refrigerant oil on the hose or part in question. A
smaller leak is detectable by adding a UV-sensitive dye to the charge,
then examining the system under a UV light. This may require coming back
after a few days, but it is amazingly effective. For even smaller leaks,
refrigerant "sniffers" are wonderful tools.

That's not a small leak, that's a freaking GUSHER! A small leak is one
that takes a year or more to affect the system performance. A medium
leak takes 6 months to a year. Anything quicker than a couple of months
is a BIG leak.

 

I agree. OP, you can solve all the mysteries with about $25 worth of R-134A,
if you're so inclined. If it works for a while and then stops, that might
be a leak. The amount of time to stop working will tell you how often you
need to get it recharged. Hopefully it'll be a long time.

 

I'm not sure I agree with your agreement.... at least not entirely ;-)

ANY leak that causes you to need a shot of R-134a more often than once
every couple of years really should be fixed. And no, its not for any
"environmentalist" reason, R-134a is pretty harmless in that regard. The
problem is that the leak also depletes the system lubricating oil, so
you periodically have to give it a shot of oil as well as refrigerant.
Every time you add a shot of refrigerant and ESPECIALLY oil, you add
some moisture to the system because R-134a compatible oils absorb
moisture as eagerly as brake fluids do. Straight from a brand new
bottle, these oils have traces of water in them. After a few oil shots
you'll have added enough moisture along with the oil to overwhelm the
dessicant drier in the AC system, and then acids will start forming and
corroding away parts even faster.