Is my car's air conditioner releasing deadly fumes or something?

August 21, 2007 3:42 PM

Is my car's air conditioner releasing deadly fumes or something?

When I turn on the AC in my car lately (since we've been having really hot weather), I notice a sort of burning in the back of my throat. I don't see or smell anything.

This seems to happen on either fresh air or recirc, but if I just run the fan, I don't notice the problem.

I'm going to take it to the mechanic, but I wanted to know if I should be worrying about it. (Generally I try not to worry about things.)

Is it some kind of coolant?

posted by exceptinsects to Travel & Transportation (3 answers total)

The refrigerant in most U.S. vehicles since 1997 has been R134a replacing the older R12 type refrigerant in vehicles built before that year. This circulates in your automobile air conditioner, alternately under high pressure outside the vehicle, carrying heat to the condenser coils up front, near the radiator, and then at low pressure, inside the passenger compartment, providing cooling power to the evaporator coil.

Neither of these refrigerants is much of a respiratory irritant, but if your condensate drain has been plugged up by mud, there may not be any way for water that condenses from air to leave your car normally. In that case, the condensed water in the evaporator coil tray provides a good place for mold to grow, and you could be sending mold spores around through your car by using the blower motor. You can check to see if the drain is working by looking under your car for a puddle of water, after the car has been standing in one spot with the air conditioner running for more than about 10 minutes on a humid day. If there is no puddle, and no evidence of water continually dripping from under the car, or if the floor mats in the passenger footwell are regularly damp (due to condensed, undrained water spilling out of the drip tray when you corner), your drain tube is plugged. You can sometimes clear the drain from under the car with a piece of coat hanger, but you need to be careful doing this, as it is pretty easy to damage the soft aluminum fins of the evaporator coil, by jamming a stiff wire up through the drain indiscriminately.

Just getting the drain to work won't, by itself, fix the skanky smell and mold spore issues of a badly neglected heater/AC system. To clean it out thoroughly usually requires significant dis-assembly of the heater/AC core airbox, under the dash, which in many vehicles, requires removal of the radio, and parts of the center console.
posted by paulsc at 6:04 PM on August 21, 2007

Something similar happened in my car. It was a coolant leak from the heater core.

1) It's a hot day.
2) The air conditioning condenser (radiator) is in front of the engine radiator in most cars, which means the heat from the A/C is in the stream of air that reaches the engine radiator.
3) The engine is under a little heavier load when the A/C is on because it has to run the compressor.

All these facts raise the amount of heat the coolant has to cope with.

On a cool morning, put the 'defrost' feature on. In general this cools (to dry) then heats (to de-mist) the air in the car. If your windshield gets foggier or doesn't de-fog properly, it's a coolant leak.
posted by jet_silver at 10:17 PM on August 21, 2007

Response by poster: Well, I took it to the mechanic and he couldn't find anything.
There is water under the car, so I don't think it's the drain problem paulsc mentioned. (Also there's no moldy smell.)
Other passengers in the car don't notice the problem either, and I find it's lessened now that the weather's cooled down some.
I think that maybe the hot weather is exacerbating some small kind of leak or making some substance in the car give off fumes, and I'm just particularly sensitive.
posted by exceptinsects at 9:55 AM on September 11, 2007