Originally Posted by spacetrace33
Thanks for all the replies. Just to verify, the A/C works perfect and it goes through the vents that it's set to use, same goes for heat. So where do I go from here? What are some tests that I can do to determine exactly what the problem, or where the problem is? And bonus question is, exactly how do the blend and the mode doors work?
Blend door is cable operated, if you turn the dial all the way to cold you should hear the door "stop" basically hit the wall in the box. If you turn it back to hot, you should hear the same "stop" sound as it hits the wall the other direction.
The mode doors are vacuum operated, if there is a leak in the vacuum line it will default to the defrost position. The vacuum solenoid is located behind the lower plastic panel below the passenger air bag key switch and your 12V lighter plug. It is toward the back (front of the cab nearest the firewall).
So I understand correctly, you can change between all settings of the mode door ok and your blend door is operating correctly. There is one small adjustment you can do with the blend door. Turn the **** so it is pointing straight up (midway between cold and hot) Slightly pull the **** out, to where it is about halfway off the post, then turn it all the way from cold to hot, it will go past the point where the blend door should close off access to cold air. Then twist the **** back to the center between hot and cold and push it back in place. This is basically a quick way to check if it is closing all the way on the hot side and automatically adjust the cable (ever so slightly to where the range ends when the door closes completely).
If after all of this you have good adjustable airflow on all three speed settings whether hot or cold, and you can switch between all modes, you can rule out the blend door and mode control.
Is your truck warming up properly? A stuck thermostat could cause a loss of heat as well.... and is cheap and easy fix.
At that point I would flush the heater core. The procedure is pretty easy. There are two lines to the heater core. You can separate one on the passenger side valve cover, and the other on the driver side valve cover.
Connect a hose fitting you can screw your garden hose into (Home Depot or Lowes is your friend)... similar to the connection on the end of the hose you connect to your faucet, and put the end of the other heater core hose into a bucket and turn on your water.
Run it until it is flowing clear water. (If you see chunks of stuff you are on to something)
Then shut off the water and switch the fitting to the other hose and repeat.
This time you are pushing water through in the other direction.
When you are done reconnect the hoses and top off your radiator.
One important point to note, you will likely have an air bubble in your cooling system at this point.
If you can elevate the front end of your truck (ramps or park on a hill) when you refill the radiator and leave the cap off while it is running (take cap off when truck is completely cooled off), you can basically burp the system by letting it completely warm up so the thermostat is wide open. Then rev it up to about 2k RPM and drop back to idle. You should see the coolant rise slightly in the neck of the radiator to indicate it being pushed by the water pump (get someone to help/watch for you if you can). Continue revving up and back to idle for about 5 minutes to ensure all air is out of the system. You can carefully squeeze the upper radiator hose (wear a glove, it's hot!) between the thermostat and radiator as well to help force any air out. Turn the truck off, top off coolant if needed, check the overflow bottle as well, and replace the cap and see if your heat is improved.