I have a question for anyone who knows. This whole summer, I have been battling and struggling to figure out why the interior of my car is so off-the-charts hotter and more humid than in any of the 15 previous summers I have spent with it in the same place. I have gone through just about every theory of what variables could have changed, and inspected and checked everything I could. The only thing that has changed between this year and last year - when I did not have these problems - is that in April, I put in a new alternator. Since the time I installed it, my lights have been dimmer and I've had voltage fluctuations, but after 4 and a half months, it hasn't "failed", and it kept testing good so I couldn't return it. But the more I thought about it, the more I wondered if there is a connection between this new really crappy alternator (reman, not new) and the AC performance drop. I didn't think there could be, but that things sure seems to blow a lot harder and colder when I rev up the engine to 2-3K instead of just sitting and letting it idle. I am just trying to suffer through the last month of the summer before things cool off but this whole summer has sucked because of whatever my problem is.

Any ideas, thoughts? Could the ALT have an impact on compressor/AC performance? What do you think?

First you need to tell Us what J body you have.Model,year,and engine while not completely needed this helps diagnosis your cars problem.I will say replacing a alternator has nothing to do with your air conditioning plain and simple!If you had some dimming light's in the interior I would strongly suggest removing ALL the ground cable's from the battery and follow any to the subframe or block and remove and clean the metal and terminals.Grounding is essential for a strong electrical system period.I will say making sure the battery is at 100% fully charged helps isolate if you have a battery issue or a grounding issue.I think your problem is a (grounding problem).I say this because if your car has run consistent over the said time since the alternator replacement the part is charging the battery and if that was not true the car would not crank or have issue's otherwise.I would suggest considering upgrading your battery ground cable and any other external grounds as some J's have extra grounds from the block to the block or subframe or even fender with NEW cables.As for the air condition issue you need to either have a shop test your AC Freon to see if you have several things going wrong.It could be just low Freon,a tired compressor,a dryer going bad,or even just some orings dried out and or leaks in general.The AC system can be checked with a machine to find and conclude if any component or part of the AC are failing and or worn out and finding leaks with a dye.I end short will say checking the ground cables in the engine bay are a (MUST) and removing them and cleaning must follow.Updating old cable's can make a world of change.Also how old is your battery and have you checked the water level (IF) you have battery caps to check the water level in the battery as HEAT can kill a battery just as cold weather can.If you have any further questions just ask.The advice is free and I hope this helps explain things a little better.

2001 Cavalier 5-speed manual 2.2 engine 207K.

OK, so last night as a test, instead of letting the AC run after I parked at idle, I tested my theory and kept my foot on the gas for 5 minutes at or a little over 2k rpm instead of the normal 1k. Big difference in how cold the ac was for sure. But i have to admit or explain that that doesn't really seem to be the true problem that is causing this summer from hell.

If you see the other (related) post here about AC vent problems, you can see how many things I have thought were the culprit. Anyway - here is REALLY what the problem is this year.

Every night, it is like someone fires up a steam-bath or sauna in the car. Every morning first thing - inside the car is like a jungle with the heat and humidity off the charts. The inside of every window is completely fogged-up and there is extreme condensation. This never happened before this summer. How can I figure out what is causing this because I think that whatever it is is cancelling-out the otherwise cold-enough output from the AC. As far as i know, the only thing that could be INSIDE the passenger cabin that would explain it would be the evaporator/heater coil compartment/box. However, i have not had any issues with water spilling out on the floorboards and no bad/sour smells either. But what else could cause what i described? And since there doesn't seem to be any way to getting to that evaporator anyway - what should I even try? I found the drain hose on the outside of the firewall, but don't want to start screwing around with things if I am just guessing.

Any clues? I won't make it another summer like this. It has truly sucked.

So, poor a/c performance and condensation inside, but no musty smell and the a/c is cold when running at higher RPM (a.k.a. compressor spinning faster). As for the condensation, I'm not sure what could cause that if you don't have a plugged up drain tube or an evaporator core that's freezing up. I would check the front carpets to make sure that they're not wet, because they might be damp and you just can't tell by looking at them. Check on both sides in the front of the carpet, where it starts to go up the firewall/bulk head.
The poor a/c performance could be an issue with your compressor not functioning as well as it should (weak compressor), a restriction in a line/component that's bypassed when the compressor is putting out higher pressures, a low refrigerant charge, maybe even a weak blower motor because of your alternator issues. You need to get some gauges on the a/c system to see what the pressures look like so you can accurately diagnose what's going on. Without that, everyone is just kind of shooting in the dark. The problem with a/c work is that, without gauges to see what the system is doing, it's very difficult to try to diagnose. And, without the proper equipment, you can't put the system in a good vacuum to evacuate the moisture after a repair to make sure the system will operate correctly when you're done. A lot of places offer free a/c performance checks, so you can start there. Or, you can just bite the bullet and pay to have someone properly diagnose it.
You can do a quick check with the car running: throw a thermometer in one of the vents and see what temperature you're getting. Also, check the low side line coming out of the evaporator, it should be cold and will probably have condensation on it. It might just be that you feel like the a/c isn't cooling properly because your alternator is weak and your blower motor isn't performing as well as it should. It could be completely separate issues between the alternator and a/c.



THE .ORG IS MY KITCHEN!

After thinking about it for a few more days, the answer HAS to be that the evaporator is freezing. It is the only place inside the car that any moisture could be repeatedly created. I have - on many, many occasions - gone through every square inch of the car searching for any water, anything that is wet or any moisture and haven't found anything. All the floor mats are bone dry, as well as underneath of them - the trunk including the spare tire well is also totally dry.

So now working from the assumption that the evap is freezing and that is where the moisture is coming from (but doesn't explain why it stays in the car overnight if the drain is not blocked). I guess that ALL of the moisture from the ice could go into the air but you would think that if the drain was in fact blocked that I would have a water / leak issue which I don't.

I am not an expert on AC systems. But I really didn't think too much about a low refrigerant problem as long as the compressor kept running, and the drier got ice-cold and cold air came out of the vents. I did check the pressure but I suppose that could have been wrong since it was a cheap piece of Walmart crap that was a few years old.

What causes an evaporator to ice/freeze up? Maybe that is the root cause of what I should be looking at.