Chemical smell coming from Heating/AC vents

Hi all,

I have a 2008 4Runner with 215,000 miles on it. After sitting for 2 weeks recently, I started it up, and immediately noticed a faint plastic smell coming through the AC ducts.

I didn’t think much of it for a few days, but then one morning, it got very strong, and smelled more like burning plastic for a short period. Since then, it has had more of a chemical smell, almost like Carburetor Cleaner, and it won’t go away.

The smell exists whether the AC is switched on or off, but it’s most noticeable if air is flowing in from the outside. In other words, if I turn the ducts to ‘Recirculate’, the smell more or less goes away.

At one point, I thought it might be the blower motor burning up, so I replaced that, along with the cabin filter, but it made zero difference.

I took it to my local mechanic, and he says he can’t find anything wrong with it.

I’m stumped….

 

Is the "fan speed" working properly? I think there is a resister that controls "fan speed"?

 

Or you let the dealership change your oil and its over full?

 

it works normally

 

No, I’ve done all my own maintenance since new.

It started suddenly after a 2 week vacation, where the car sat unused.

 

Hmmm, have you considered a coolant leak starting inside heater coils for cabin heat?

 

That’s my guess antifreeze is what your smelling leak in heater core.

 

I really don’t believe it’s antifreeze. Having owned vintage cars all my life, I’m very familiar with the dreaded smell of a coolant leak.

Antifreeze has a very distinctive, almost sweet smell, whereas this is a very pungent smell….like burning plastic, mixed with a solvent.

 

That's the neighbors burning trash up wind. Just let it pass and wait for the air to drop.

 

I always thought the people stealing catalitic converters are installing them in their house?

 

Mine occasionally has that smell at startup. Coincidentally my AC has been blowing warmer so I recharged the system and the AC blows cold now but I still get the smell sometimes. Assuming it's a small leak in the AC system and perhaps yours is leaking also

 

This is most likely the AC leaking refrigerant in the air box behind the dash.
There is an o-ring fitting holding the two lines to the evaporator in the box. Those o-rings will dry and crack and allow the refrigerant to leak into the box. Its super hard to find and test for, you gotta strip the whole interior out to get to it.
It probably wont be long until the AC quits working. As the refrigerant leaks out the pressure drops. There is a pressure sensor in the line and once the pressure gets too low the AC system will quit working. The compressor wont kick on when the pressure gets low as a safety factor to keep from burning up the compressor. You'll likely get by another year or so putting a can of freon in it every few months. Eventually the o-ring seal will blow out and piss out all your freon at once and then you gotta rip everything apart and replace the evaporator, lines, and heater core if you want to keep the AC system going.

 

Is it THAT hard on a 4th gen? Because the evaporator with expansion valve was like 6 bolts for my 3rd gen. Ive never seen something so easy.

 

Thanks, I was afraid this could be the case.

One of the first things I googled was what refrigerant smells like. A lot of sources claim it’s odorless, and a couple of the sources claimed that if the leak was bad enough to smell, then all of the refrigerant would be lost very quickly. I did find one source that said it smelled like burning plastic, so I’ve been thinking this could be the case.

I do remember the system lost all pressure about 10-12 years ago…I charged it up with one of those cans from the auto parts store, and it has been working well ever since. I guess I’ve been on borrowed time for a while now….

 

i think the book pays 16 hours and its going to take two people about 12 to make it happen. Basically the whole interior comes out, steering column drops down, i've had to take the passengers seat out before. Then you better hope the owner doesnt have any stereo stuff hooked up behind the dash with wires everywhere. You gotta pull out the whole dash brace that bolts between the two A-pillars.

 

Yeah it has a funny weird chemical metallic smell. Sometimes they smell like pool chlorine, sometimes its a weird plastic smell. Thats the refrigerant leaking out and the blowers blowing it in your face. Thankfully they are using the newer stuff without CFC's so you're not fumigating yourself in the cab with aerosolized cancer.

Also, if it lost prime and you were able to recharge it and get 10 years then yeah thats great. Normally when they start leaking its about a can every year, then a can every six months, then a can every month, then one day the seal just gives out. I have seen them normally last about 2-4 years once they start leaking and about the age you are at, is where they normally go downhill quick. You might can take it to an AC shop and they evacuate the system and pump it full of oil which conditions the seals and then recharge it. You might get another year or so but yes its most likely going to go bad here in the near future.