I have an 07 1500 big Horn. At normal operating temp the gauge drops then blows cold air, if I increase the rpm the gauge goes up and blows hot air. Also I can smell warm coolant when warming the truck up. Levels are topped off. Am I looking at air in system or bad cap, not holding pressure or t-stat?

 

Troy, if you are smelling the coolant on the inside of your truck then you more than likely need to replace your heater core. What you are describing are all symptoms of that. Is your carpeting a little damp on the passenger side up under the dash near your heater box?

 

The coolant smell is while I an outside the truck

 

Troy,No, you are not looking at air in system or bad cap, not holding pressure or t-stat. Ruffone is right: check under the carpet in the passenger front floor. Pull the carpet back and stick your hand down in there and find out if it is wet. If it is, its your heater core. So, check the following:1. Are you smelling the coolant inside the truck?2. Are your windows fogging up a bit when warming the truck?3. Is there a funky residue on the interior windshield?Also, your blend doors may be malfunctioning or broken. So are you:1. Getting heat on both sides?2. Any other areas not deliver heat, or very slowed airflow?I just overhauled my HVAC box a week ago. 2003 Ram 1500 Mega Cab. Keep us posted.
DDay77

 

The coolant smell is from the outside of the truck. The floor is dry and foggy windows because the air temp is 13 below. But the floor has minimal air flow. Would the blend door cause the temp of the air to drop at idle then heat up at cruising speed? Now it doesn't do it all the time, but I have noticed it alot.

 

Heater getting hotter with engine RPM is generally an indication of being low on coolant.

 

Coolant is full.

 

You have a leak somewhere, and likely have air trapped in the system.

 

Just wanted to keep everyone up-to date. Took to a mechanic, bad water pump and air in the heater core. He also replaced the thermostat just be on the safe side. All better now. "blend doors" need work next, but have to wait till I have more money. The heat works and that's all that matters for now. The door is stuck. It blows half floor and half defrost. Can live with that for now.