Hello, I got my truck used about a year ago. 280,000 miles,still cranking. The heater decided to go out as soon as I moved to Denver. I do have another issue though,upon acceleration I hear a door opening(outside air?). Let off the gas or idle I can hear it shut.In this weather it's annoying.Vacuum leak or valve? Also the fan switch only works on high and the dash is falling apart,although I knew that when I bought it. I want to repair it all when I go in to replace the core.Appreciate any feedback or help.

 

Moved this post to it's own thread.....

Do a search in the DIY section on Wild Vents. That will be part of your problem.

For the fan, probably the resistor block. It's in the heater box, down by the fan.

Do the evap core as well while you are in there, if you have A/C.