Why does my defroster and heater only blow out cold air in my 2004 dodge intrepid

2009 Mercury Mountaineer, my heater wont work unless I'm driving and get over 50 mph... I let my car warm up for 20-30 minutes and it wont defrost my windshield, it only blows cold air.

Blower motor resistors are super common failures in these. The connector for it can also get melted.

I had a similar problem with my 2003 intrepid. The problem turned out to be the control panel. I went to a salvage yard and got one.

The Intrepid doesn't have a vacuum line. It uses a electric motor called a "blend door actuator". It's located on the underside of the heater box near the center of the car.

vacuum down to 30 inches for an hour recharge let me know what kind of readings you have

This sounds like your automatic climate control is starting to malfunction. Check to make sure your coolant is full, and temp is not fluctuating, and when your vehicle is warmed up, try using the low setting and feel for air temp. Is it warmer than if you turn it up? When at idle the vehicle is not producing heat the same as if you are driving, putting load on your engine and more air/fuel combustion means more heat, which is why you can feel heat while driving. Ideally you should feel heat as soon as the engine is warming up, getting hotter as it reaches peak temp of 190-210 degrees. You can try to make sure your water control valve is not blocked, and all electrical connections are secure. This will be located close to your firewall and connected to the coolant tubes that run into your firewall to your heater-core. Also use recirc (setting)to try to summon as much heat as possible, however ultimately, you may need to take you vehicle in for service. If it only warms when driving defrost will be an issue. Good luck.

sounds like a weak waterpump or low level

It sounds like you have a blend air door stuck. This is in the housing of the heater a/c blower unit under the passenger side of the dash. There is a motor on the top of the housing that could possibly be stuck or on working.

I have a 96 Intrepid, and none of the signal lights work. I tried replacing the fuse, but this did not remedy the problem. Could this be a loose connection?

First check the coolant level in the radiator. Check your heater core hoses on the firewall underneath the hood. Let the car come up to temp. and feel the two hoses. If only one of them is getting hot you may have bad heater core or a bad heater control valve.