1999 Chevy Blazer 6 cyl Two Wheel Drive Automatic 136000 miles
This started when I replaced the battery. The A/C worked before new battery installed. Afterwards, the A/C worked however extremely hot air was coming through the vents no matter what temperature setting was. Also really bad smell was coming in as well - smelled like antifreeze. Checked all fuses and they were fine. Coolant levels fine. My mechanic had to clamp off recycling hose to prevent heat from coming through vents. My mechanic checked out motor that controlled the vents and replaced the actuator which got the vents working again, but could still smell odor. My heating coil is not broken - no dripping onto floor boards or spraying of windshield. No leak in the radiator either -- water level and antifreeze are fine. Weird part is that odor comes through whether I have the defrost on, or just using outside air, cold setting or hot setting. Smell is stronger when the Defrost is on and temperature setting is on 78-82. Smell not as strong when temperature setting on 65 and using outside air. My compressor is leaking but by now all of my coolant is gone. Concerned that odor not going away and the more I use the heat the worse it gets.
The heater core sounds like the culprit, have it doublechecked. If you smell it with the blower on in the car it is usually the problem. Both temp settings you tried use outside air, on 65- no heater core airflow, 78-82 w defrost on uses the a/c for the defrost and then you have it on hot by the temp selector which opens the blend door to the heater core. As far as nasty smelling vent in cars, I have had good luck using " Ozium", most parts stores have it. Turn blower on High, temp in the middle with dash and foot nents on and spray it into the grille at the base of the windshield outside the car. Let car air out after you do this