HVAC Issues

[97_ExplorerSport]

I've poked around on the forum for awhile, but haven't totally found what I need. Please excuse me and direct me to the link if this is already out there.

Anyway, I have a 97 Sport Control Track I bought about a year ago. Fast forward to this summer I needed the AC of course, and hot air was dumping out the floor vents. Eventually figured it out and replaced the bypass valve with an OEM motocraft one. This let me regain control over the AC, but it only worked on max.

Fast forward to this winter, and my heat is acting up. I can use any of the vents, but the heat only works on max. I have no control over the temperature of the heat via climate control. I suspected it was the blend door actuator, so I ran down to my local junkyard and pulled one off another sport. I had an absolute bear of a time putting the new one on. I took apart my old one (which I'm pretty sure worked) and used the shaft to confirm the blend door worked, which it did.

3 hours of cursing, cut hands, and a lost 8mm socket, I got the actuator on the shaft. I cut a little access panel in the heater box to make sure, and when the heat is on OFF, I can turn the knob and see that it moved like it's supposed.

Once I turn on the heat to any vent setting, I can see the blend door shut closed and I have no control over the temp once again.

I'm losing my wits end. Could it be another vacuum leak?

 

[BrooklynBay]

Welcome to this forum! Have you checked the vacuum controls for leaks?

 

[97_ExplorerSport]

Thank you! Are you talking about the vacuum lines behind the climate control switches? Or the vacuum plenum under the fender liner?

It makes no sense to me, why the blend door works under no heat/ac, but when the heat is turned on (excluding max AC) it kicks closed.

 

[BrooklynBay]

Check all of the vacuum lines behind the controls, vacuum reserve tank, and the servos for leaks.

 

[97_ExplorerSport]

Where would you check those? Except the lines behind the controls.

 

[BrooklynBay]

Sometimes the hard plastic tubing going into rubber boots on servos & fittings develops cracks over time. Take a look at the vacuum diagram under the hood.

 

[97_ExplorerSport]

I'll have to take another look behind the glove box, and take the fender liner out to take a look at the plenum ball. I'll let you know what I find, if anything.

 

[skydude]

Same issue

Hi! I have the same issue. Replaced the blend door. I works with temperature control but the same cool air comes out at all settings... It'd be great if you share what you find out.
Chris