No heat - 97 windstar 3.0L

I am currently having issues with the heat in my '97 Windstar 3.0
I have owned it for 2 years and have had no problems with neither the heating nor the a/c in the front, however the rear system has only blown very hot air when turned on, even when the a/c system was turned on. We just kept the rear system off in the summer.

This was like this until a couple days ago. Now when I turn on the fan only the air from outside is coming into the cabin, it is not being warmed up. The engine warms up fine, but not the air. This is happening with both the front and rear venting systems. Can anyone help me to determine what the cause is? I thought it was the heater core, but since it's happening to both front/rear systems I wasn't sure.

Any help would be greatly appreciated.
Thank you,
martinimos

Hopefully, someone more familiar than me with the 97 will correct me or add to what I can suggest, as I am more familiar with my 95. If I understand .ou correctly, when you turn on the ac in the back, the heat is still on back there too? So, is the air blowing out the upper/ceiling vents hot or cold? Is there still hot air blowing out the floor vents that are for the heat only? My 95 has hot coolant always going to the back heater core just as the front heater core. The back one however, can still give you a hot foot even if the fan isn't on. Mine has no temperature control for the heat or ac, just fan control. Later models added temp control. If what you have doesn't operate like mine but has the same kind of controls, you may be having a vacuum problem. Vacuum is used to control the doors inside the air boxes to control air direction. The front box also has the temp regulating done with vacuum operated doors. If disconnected, I'd think you would notice a hissing or sucking sound inside the rear box compartment, underneath the van under the rear box, under the hood, or under the dash. I'd also would think you'd either have engine performance issues and/or cel codes. If you have temp control in the back, there is a vacuum line that goes to a heater control valve that's underneath the van under the rear air box.

Not having heat at all may be unrelated to the original heat issue in the back that may be vacuum related, but a flow/pressure problem either caused by a faulty thermostat that's probably stuck open all the time, blockage, or water pump failure due to the wearing down of the pump blades. So, I'd suggest finding the heater core hoses for the front and rear heater cores. They start as one hose at the thermostat, split behind the engine just before making entry through the firewall to under the dash and the other side dives down under the van behind the trans to the back. They should all be hot. The heater hose at the rear temp control valve underneath may be cold if the valve is closed. The return hose to the water pump likewise splits or really joins the two lines from the front and back between the engine and the fire wall. These three should also be hot, with exception to the the back one if the valve is closed. The back lines are supposed to be hot with the rear control set to hot, and always hot if you don't have temp controls.

Rather than going into all the possible blockage locations, where you detect heat, no heat, flow, pressure, no flow, no pressure, etc., will be easier for you and us to figure out what's going on. It would be worth while to start up the van cold and see how soon you feel heat, flow and pressure in the upper radiator hose. You shouldn't have all of those until the coolant is HOT. As I said before, you may have an open or opening too early thermostat.

I don't know if this applies to 1997 models, but a very common Windstar problem for no heat is a failed blend door or blend door actuator. Do a search on these on this forum and you will find a lot.

Things to check....

Coolant level..
Heat in heater core.
Vacuum acutators.
Vacuum controls.

I had the problem in the back (same as you described) in my '96. It was caused by a problem in a selector switch on the front panel. The switch did not transfer the vacuum to the rear actuator, and behaved as if clogged. I repplaced it with a new on from Ford. I don't recall for certain which of the controls was replaced. It might have been the one on the right that controls the rear heat fan and selects heating or cooling.