Theres a weird odor when I put a/c or heat on. What would it be?

2003 Merc Grand Marquis.

210K miles

Car is great

When I put the a/c or heat I smell something through the air flow vents like anti-freeze but I check the level and its full.

Anyone know what this may be?


There are no leaks on the ground at all

3 Answers

  • roger
    Lv 7
    9 years ago
    Favorite Answer

    If it smelled kind of mildewey this is a common problem , and there is a spray made for that my mechanic uses that takes a few minutes to apply up under the hood.

  • Anonymous
    9 years ago

    Check the passenger side carpet all the way up unto the firewall. If it is wet, it is your heater core and it is an expensive item to replace not to be done by some backyard mechanic. The dash has to be completely removed and replaced along with having to drop the steering wheel and possibly remove passenger seat for work room. I recommend using Sierra anti-freeze after you flush the system completely.

    As far as your odor... well it is possible someone already replace the core and did not bother to eliminate the odor in the vents. Just about all Auto-Parts stores carry a A/C vent deodorizer or you can use a can of Ozium also found at the stores.

    Put the A/c on auto and spray some on the passanger side ouside around the winshield wiper shaft. You'll see a vent area there. Let it run for about 2-3 minutes and then change the A/c setting to Max and spray again under the glove box. This should eliminate the odor, if not repeat procedure.

  • 9 years ago

    could be the heater core leaking. this is a common problem.

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