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Well, I'm out of ideas.

Lately I've been smelling a burning smell through the vents that is strongest when sitting idle at a stop. I opened the hood at a gas station to take a look and found that my AC lines were frozen to the point of being white. The engine was making cycling noise as if something was drawing on it too, but the AC wasn't turned on. So I turn on and crank the AC and the lines begin to defrost but the smell gets stronger until all of the sudden a whoosh sound and a cloud under the engine bay (like a time machine, a DeLorean time machine specifically). It suddenly stops as if it sealed itself or as if it was a pressure relief valve. It startled us a bit so I turned off the system and just drove home.

The car doesn't overheat and the oil level is fine, so I'm thinking the AC system is on the fritz. Odd thing is though that it still blows great cold air on a warm day as if it's working great. There's no smoke, no steam either but there's a burning smell. I checked the serpentine belt for wear or rubber shavings and found nothing. Could it be the catalyst?

Any suggestions? This car is starting to develop problems now that it's paid off. I'm starting to think they have a remote "kill switch" or something

The only way the lines could be iced over, is if the compressor is turning. The clutch may be stuck in the engaged position, either by an electrical short, or the clutch has welded itself so the compressor runs constant.

The burning smell could be the condenser (hot side) overheating. The sound you heard was prolly excess pressure being blown off. If the compressor is running with out a signal from the PCM/HVAC controls, the fan will not run, causing it to get hot on the engine bay side of the system.

Try unplugging the connector at the compressor (engine off)to see if it doesn't spin when the engine is started. If it is spinning, then the clutch is bad.

Thanks for the reply. I checked yesterday to see if the compressor was engaging or not and it would catch, switch off, catch again, etc. So it doesn't seem like it's always on and the fan does run constantly if the AC is on. Still blows cold air too.

There's nothing leaking under the car and I can't pinpoint where the smell is coming from under the hood. It only seems to smell after driving and coming to a stop at a light or something. If I switch over to recirculate, the smell lessons quite a bit, so it's being drawn through the cowl vents.

neonsox wrote: It only seems to smell after driving and coming to a stop at a light or something. If I switch over to recirculate, the smell lessons quite a bit, so it's being drawn through the cowl vents.

Not saying that this is the reason for the problem you are experiencing;
When I changed my transmission fluid, I slightly overfilled it. I would smell it whenever I came to a stop. Drained a bit a out and all was well. Again, not saying this is the cause of your problem but might want to check TF for condition and quantity.

I should mention that it's a manual, so I believe it uses oil. I will check the level this afternoon, but how would that level have changed if the case has never been opened (or even the plug)?

neonsox wrote:I should mention that it's a manual, so I believe it uses oil. I will check the level this afternoon, but how would that level have changed if the case has never been opened (or even the plug)?

As I said;
Not saying that this is the reason for the problem you are experiencing.

Which AC lines were frozen specifically? Typically when something freezes in certain parts of the system it means there is a restriction in the system. Also, if the AC was cycling constantly on a cold day it is possible that it got too cold. The burning smell may have come from one of a few things, such as your blower motor, resistor bridge, or more likely the AC switch and/or circuit on the back of your HVAC panel. Since those are all very closely related electrically speaking, it's hard to pinpoint anything.

The two lines that run on the passenger side of the engine bay were a solid white color. I believe these lines go from the dryer to the compressor. I haven't seen it happen since then, but the smell is there. It's been kind of cold here in the Northeast, so I'm not sure the compressor will engage during the cold weather.

Could the transmission oil be low? Wouldn't that create a whine or a studder instead of a burning smell though? The engine has a skip when making turns at low RPM but I was told that was a sensor on the throttle body that needed cleaning (and maybe the TB plate).

This one is making me