My 2010 dodge charger has run into some heating issues. The engine started not coming up to temperature. Check engine light came on and I scanned the code which came up as p0128, if I remember correctly, which was thermostat failure. I have no replaced the tstat twice and still having heating issues. When idling the engine comes up to temperature and heater and defrost work awesome. As soon as I start to drove the engine loses temperature and the car starts blowing colder and colder air until the check engine light comes on. I scanned it again and now the code is P2181. Have been fighting with this issue for a bit now and hope someone can point me on the right direction.

3.5L V6 engine, coolant level fine and tstat replaced twice.

 

What brand thermostat? When I was working on my volkswagens, I would buy three or four thermostats, just to make sure I got one that worked. I was NEVER able to change it just once..... Stant is a good brand, but, stay away from the 'safety' stats. They suck.

 

I cant remember the brands but I bought the first from APC and the second from CarQuest. Because the engine and heat in the car work at idle makes me think it is not the tstat.

 

At idle, you are generally sitting still, with very little airflow thru the radiator. So, the coolant actually gets hot. Start moving, and all that changes. The radiator can shed heat a LOT faster than the engine can produce it when the vehicle is actually moving. Faster you go, the more effective the radiator is. So, coolant temp drops like a rock.

The ONLY thing regulating coolant flow, is the thermostat. If it isn't doing its job, nothing else will either.