I have a 2003 Dodge Ram with 4.7L engine. I am having some heater problems that i hope you guys can help me with. The problem that i am most concerned with is that the heat coming out of the defrost vents is not nearly as hot as it used to be. Also the heat seems to be slightly warmer if the fan is on a lower setting and as the speed of the fan is increased the air becomes cooler. I have recently replaced the thermostat, because i thought that was why the air was not as hot, but that did not solve my problem either. I have checked the level of the coolant and it is fine. I have been reading about the heater treater blend door replacements, but im not sure if that would cause the air to get cooler as the fan speed increases and im also not sure which "door" would need to be checked or replaced. I only use my defrost for heat, i do NOT use the vents or floor vents so i really am not that concerned about those. Any help or advice would greatly be appreciated, i am kinda stuck and do not want to start tearing out my dash if it could possibly be something else.