I have a 97' Ford Ranger 4x4 with a 4.0 sohc. I bought it about a year ago, and the heat has never worked. Any switch I flip it to will only force air through the defroster. That and the truck itself takes forever to warm up; it can run for a half hour before driving it and the temp gauge will still be below zero. Occasionally it will warm up when it feels like it. Regardless I would like to find a way of fixing it seeing as Chicago winters are pretty cold. I think the truck heating itself may be due to a stuck thermostat? And that I should replace it with a low-temp therm, which is what I was told, but I would like some other opinions on the matter, that and how do I fix my heat so it actually blows like it should, rather than just going through the defroster. Any help would be greatly appreciated. Thank you!

 

well you could try replacing the blower and heating core

 

My 97 did the same. I do have a OHV though. It never went above cold unless it was really hot out. I replaced the stat with a 195. I believe stock was 190. With the 190 it was always open. A lower temp stat would just make your issue worse, u have to go higher. Or yours could just be stuck open. I'd try replacing it to fix that issue. Regarding your other issue I think there is some type flap in there that controls where the heat comes out of. Not sure what it is called or how you fix it. Sorry.

 

Blend door is what i think jtfoxman is talking abt and yes new stat at least a 190 if not 195, do yourself a favor buy the expensive one(high performance) they are less likey to fail. blead the air out of your coolant system when your done or you will have problems with your truck heating up. now if your truck heats up, the heater hoses get hot(at least warm) and you have no heat, it may be the blend door not working, it could be the blend door motor or a broken blend door. there are several threads about blend door problems.
Hope some of this helps

 

did someone swap the SOHC in?

 

When it defaults to the defroster, there is a vacuum leak for the part that controls which ductwork to flow. On mine, the control diaphragm is run by the blue vacuum line and is located down by the gas pedal. I had a leak elsewhere on my truck that robbed vacuum from that diaphragm. If you have a mighty-vac with a gauge, or some other vac gauge, start checking vacuum levels. This thread helped me out a lot:
2nd Gen NO AC ( or heat) FROM VENTS!!! A "How to" what to look for thread - Ford Explorer Ranger Enthusiasts "Serious Explorations"®

As a reference, my source vacuum line was at 17 inches of Hg in the engine bay. The black vacuum line behind the glove box is the "source" line for all diaphragms...might be a good one to check to see if you have vacuum at all in the cab.