Originally Posted by 97fr4x4
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!
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.
Mine: '98 Ranger XLT 3.0L SuperCab w/ manual 4x4 "Off Road" 193k miles
Wife: '07 Mitsubishi Outlander LS AWD 3.0L 128k miles
My 3.0 puts out 150HP...hers puts 220HP...something is wrong here!
Future Restoration: '77 Chevy 2WD K5 Blazer