I have a 1998 4 cylinder 2.5L automatc Ranger and my heater isn't working either. I thought it was a thermostat problem, because on the way to work Monday morning with the temps in the low 30s, it took approx 40 minutes before the temp gauge rose to normal and the heater air got hot. Assuming that the t-stat was stuck open. And then in the afternoon with the ambiant temps in the 60s, the temp gauge was normal while moving but jumped to nearly H when stopped, so it wasn't opening enough.
With those symptoms, I decided to replace the t-stat. I did that today and now the temp gauge will not go above the C and the heater remains blowing cold air. FYI... I did flushed the radiator. The two heater core pipes are hot along with the upper radiator hose. It acts as if the new t-stat is stuck open. Oh and get this, I took the old t-stat and put it on the stove with boiling water and it works fine. Opens in the boiling water and closes when dropped in cold tap water.
I am completely clueless as I've worked on other vechiles with similar problems and the t-stat replacement normally fixes it. Any ideas or comments would be greatly appreciated.
Thank you,
Jeremy/Jackson,GA