The rusty color of the water that had been running out could be a sign of a leaking heater core. Have you checked to see if the coolant level is low? If not check that first, and let me know. If level is ok, then we will go from there.
Ok, what we need to do at this point to find out if the ac drain is clogged is to pull the blower motor so you can stick you hand in the hvac opening to feel if it has standing water in it.
This isnt very hard and only takes about 10 minutes to achieve. The blower motor is located behind and underneath the right side of the dash.
Fig. Blower wheel (1) and blower motor (2)
If it is wet or has standing water in it, then the drain is clogged and will need to be cleaned out, but the dash doesnt have to come out for this. The vehicle does need to be about 6ft in the air. The drain is towards the bottom of the firewall on the engine side. A shop can use a straightened coat hanger to insert in it and unclog the drain. It should be about 1/2 hour labor at the most.
A dealership wont do this for you, but a good independent shop will.
It might be related. If the water that did come out before the drain clogged dripped down onto the metal frame, it will turn it a rusty color.
Since you are not losing coolant, I am not overly concerned about the color of the water. If you were low on coolant, then we would have something to worry about.
Do you think this could have been similar prolem/answer to when it was "spraying" out last summer on the passenger side (I could hear sloshing as well). What determines what side the leaks are on? (What side might be clogged??) And, if this is such a relatively easy fix, why when I had them look for the clogged drain, my oil change place 1) couldn't find it when they raised the car up, and 2) when I went to a Transmission and A/C place (not a dealership) they had to do the intensive labor procedure to unclog it. (They said it was full of pine needles...) Is it just that hard to locate on this type of car?? Also, any insight into why this has done this similar problem two years in a row (and basically twice in one "full year") and has never had this problem before? Is it just a sign on my car getting older?
This could very well be a repeat of what previously happened. Although the drain is on the passenger side, it is close to the middle of the dash, and the hvac housing does stretch to part of the driver's side, so it is possible for it to leak out of either side.
Most oil change places do not have employees that are ase certified mechanics that actually know what to look for as far as find the drain. They are high school graduates that know basically how to change the oil and other fluids.
If the hvac housing was truly filled with pine needles, which can happen if you park outside underneath pine trees, then yes the dash has to come out to take apart the hvac housing and clean it out. If this is again the case, you should be able to feel the pine needles thru the blower motor opening.
The other possibility unfortunately, is that you were taken advantage of by the repair shop.
Pine needles, leaves and other debris can enter the hvac housing thru the fresh air ducts that are located between the hood and windshield underneath the cowling. You can look into having the cowling removed and mesh placed there to catch the debris to prevent this from happening again.
With cars being parked outside, I have had them come in 2 or more times a year to have the drain unclogged due to debris