I drive 2006 Honda Accord. I got this car last summer. When heater is on, it smells. At first, it smelled like muffins. 
But after a few weeks, the smell became worse, and now it smells like kinds of potato chips.
My mechanic checked air cabin filter, and he said the filter was not the cause of the problem and he thought something was stuck inside. But he also asked me to pay $85/hour to diagnose in detail.
Is there any way to check and (hopefully) fix it myself? I donât have any experience in car repair.
If the smell is âsweetâ, then the likely problem is a leaking heater core.
This should be diagnosed properly, because if it is a leaking heater core, your cooling system will wind up low on coolant, possibly leading to overheatingâand severely damaging the engine.
And, if you breathe aerosolized coolant for more than a brief period of time, it can lead to some very nasty lung problemsâincluding pneumonia.
The cost to replace the heater core can beâŠstaggeringâŠdue to the high labor costs, but the ultimate cost of not doing it is much higher. Get this diagnosed soon.
If it starts to have a sour smell like âstale currieâ, itâs definitely the heater core. But you or your mechanic have to make sure the air plenum does not have somthing dead in it.
I use an air condioner freshener at $8 per can. You spray this from the outside into the air intake duct with the car running and the heater and later the A/C on (windowns open). If the smell disapperas after this, you had something decomposing in the air ducts. If not, itâs defintely the heater core.
So, save yourself $85-8=$77 by going this route. If the windshield fogs up as well as smells, when you turn on the defrosters, itâs definitely the heater core.
I have replaced 3 of these over the last 25 years and the symptoms are all the same.
Replacing the heater core ranges from not too bad to very expensive. On my Ford Granada it was 8 hours labor plus parts, while on a rear drive Caprice, it was only $250 total.
Thank you! If the heater core is leaking, I donât worry about the charge. My car is still covered by factory warranty. And I donât think it is a sour smell. Moreover, the mechanic said he was thinking that something like air freshener stuck inside. But Iâm worrying because the windshield fogs up much more than other cars during last winter.
What I am also curious about is that it does not smell when air conditioner in on. And even when heater is on, if pulling exterior air, it smells less.
Anyway, I have to take a look at the air plenum.
âMy car is still covered by factory warranty.â
Are you sure about that?
If you bought an extended warranty from Honda, and if it is the âpremium levelâ extended warranty, then you will likely be covered. If it a lower level extended Honda warranty, it likely covers only the powertrainâand a heater core is not part of the powertrain.
If you bought an extended warranty from anyone other than Honda, it likely covers nothing âwhen push comes to shoveâ. Most people who buy these âindependentâ extended warranties find out the hard way that they spent their money in vain, due to almost total lack of coverage, based on obscure technicalities.
If you are relying on the warranties that are standard with a new car, I think that you need to re-read the details. The âBumper-to-Bumperâ warranty usually runs no more than 3 yrs/36k miles (whichever comes first). The standard Powertrain Warranty runs forâŠperhaps 5 yrs/60k miles, but as I pointed out earlier, the heater core is NOT part of the powertrain.
What type of warranty are you referring to?
Thank you for your advice. My car was a certified used one. As I know, Honda gave me additional one year, 12,000 miles bumper-to-bumper warranty from the date I purchased it. (I also receive a warranty certificate from Honda.) Iâm sorry for the word âfactoryâ.