A/C test procedure

Can anyone tell me how to determine whether or not the A/C in a 98 SL2
is working properly? In other words, how do I tell if it's blowing
enough air and if it's cold enough? I had it serviced, and they added 6
oz of refrigerant. They didn't check the air flow at all, so I think
I'm going to have them look at that. But I was hoping to be able to
test that myself and compare it to other Saturns somehow before I take
it in. Thanks in advance.

 

I use the following rules of thumb -

get a thermometer and place it in the duct outlet. the discharge temperature
should be 15-20 degrees lower than outside ambient temperature.

Check that on a humid day, there is condensate coming from the evaporator
drain. Also check for condensation on the suction line to the compressor.
The line should be a bit cool, if it is warm or frosted, there is something
wrong.

Check that the compressor discharge line is hot, about 180F and that the
radiator fan is running to cool the condenser.

Short of getting a gauge set and testing pressures, that's the best you can
do. System might also have been contaminated and needs a new receiver/drier
and a complete pump-down and refill.

_________________
| Can anyone tell me how to determine whether or not the A/C in a 98 SL2
| is working properly? In other words, how do I tell if it's blowing
| enough air and if it's cold enough? I had it serviced, and they added 6
| oz of refrigerant. They didn't check the air flow at all, so I think
| I'm going to have them look at that. But I was hoping to be able to
| test that myself and compare it to other Saturns somehow before I take
| it in. Thanks in advance.

 

OK, we don't have humid days, so that's out. I think they did a
pump-down and refill, but I'll check the other things you mention.
Thanks. Any ideas on how to test the air flow?

 

Actually, this should be 30F+ lower than ambient unless the system is
not working correctly or the ambient temperature is below ~65-70F.

That's certainly interesting to watch, but unecessary unless you've got
condensate soaking into your carpet. No need to look for frosty A/C
lines in the engine compartment. If they're not frosty you'll know as
there won't be any cold air. These days, those lines are usually well
insulated as well so you might not see any condensation/frost even if
it's working like a champ.

The fan is very important. Also check to make sure the compressor is
actually engaging. If the A/C clutch doesn't engage, the compressor
isn't really doing anything.

Checking the pressures should be one of the first orders of business.
You can tell a LOT by the high and low side pressures (or lack thereof).

Cheers,

 

If they only used 6 oz of coolant, it was only a top off not a purge and
refill. Off the top of my head, the usual full charge is 2-3lb.

As otherwise mentioned, check that the condenser and evaporator fans are
running properly, 'properly' being somewhat subjective... The exposed
condenser fan should rotate smoothly when flipped by hand. Bearings should
be firm and no play in the shaft. Check the condition of the compressor
clutch faces that they are not badly worn or scored that would allow slip.
If the condenser is doing its job, the temperature at the receiver/drier to
expansion valve line should be about 10F above ambient.

No humid days? Must be in Arizona or that area. That's the area where the
evaporative coolers would work. About 40 years ago I saw this device that
hooked over the window that was an evaporative cooler. Just add water and as
you drive, outside air was pulled over a wet membrane. As the water
evaporated, it cooled the air which was ducted into the car. Neat idea but
won't work in humid air.

Was speaking with a new neighbor that just moved in. As I was starting to
complain about the spate of hot and humid weather we are having in the Metro
NYC area, he said that they came from Louisiana. I stopped right there and
said, "so this is bone dry by your standards." <G>