So to say the least I am frustrated. I have a 99 Dodge 1500 4x4. The heat went out a few months with the heater core. So over the weekend I replaced the heater core and put in a new thermostat. And I still have no heat. I have been racking my brain to figure this out. I have heard that potentially air in the system may cause this. One of the things that also has me stumped is that the tem gauge dosent register. However when I was pulling a trailor a month ago the engine was obviousley working harder, the tem guage started to work and the heater started to blow hot air. Could it be a bad sensor? Any help would be apreciated!

 

Welcome to DF
I will be sending your post the section that maybe able to help answer your questions.

 

Mabe a dumb question... is you coolant level full?

 

i would probably guess you have you have the wrong thermostat installed. the temp gauge on my 81 would not move much until i swapped from 160*F to 195*F thermostat. now it moves more fairly good.

 

Coolant level was full as well as resovoir. Also when I pulled the thermostat the truck was still warm and it was open.

 

The cooling system needs to be flushed. When is the last time the heater core hoses were changed?

 

You could have two issues going on.
No heat in cabin could be the switch or vacuum motor for the trap door. You may not be getting air to blow by the heater core.
No heat registering on your dash gauge could be the gauge or sensor.

 

Check the Rad; is it hot or cold..

I had no heat condition and i back flushed the heater core with a water hose; then refilled up with fresh antifreeze and it worked great.

 

sounds like it is the wrong thermostat or it is sticking open. if it does not close your truck will not hit operating temperature.

 

Wow all great information thanks so much for all of the info. I will give these solutions a try in the next few days. What a great forum for information!!