Heater not working properly in cold weather

1999 PONTIAC GRAND PRIX

287,103 MILES • 3.8L • V6 • 2WD • AUTOMATIC

JR47

MEMBER
115 POSTS

The car provides some heat but it's not enough in very low/cold temperatures. The car doesn't overheat or have any coolant leaks. I do have a low coolant light that pops on and off almost daily that's been narrowed down to being a bad coolant level sensor just haven't got around to changing it yet. Personally, I don't mind it but would like it to work properly when I have others in the car with me.

Feb 19, 2022 at 8:58 PM

SQM

✓Experienced Mechanic
6,383 POSTS

Hello,

This could be due to a stuck open thermostat.
If the thermostat fails in stuck open position, it will not allow the engine to reach operating temperature. Which will lead to the heater not being able to blow warm/hot air due to the coolant being lower than idea temperature.

Usually this will be noticeable on the temperature gauge, as it will not reach the operating temperature range on the gauge.
The operating temperature for this engine is 188F to 206F. So, if the engine is not reaching that temperature, it could be due to a stuck open thermostat.

https://www.2carpros.com/articles/how-an-engine-thermostat-works
https://www.2carpros.com/articles/replace-thermostat

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.

Images (Click to enlarge)

Professional Diagram for 2CarPros Members
Click here to log in and view diagram.

Feb 20, 2022 at 11:45 AM