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.

Reply to
Ratbert
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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.

Reply to
Oppie

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?

Reply to
Ratbert

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,

Reply to
Ritz

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."

Reply to
Oppie

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