I have a 2001 Explorer Sport Trak, 82000 miles, keep up on all maintnence..

Recently (2 times about 3-4 weeks apart) I had instances where I was getting cold air out of the vents with controls on full heat and full fan turned on..

-Normally, starting from a cold start, I begin to get heat once the temp guage gets above the "C" line..
-Also normally the Temp guage stays just blow the mid point reguardless of driving speed and temp setting and outdoor temp.. (and goes to Cold when it's cold so shouldn't be stuck)

**The following things were common in both cases..
-Temp below 32deg. (outside)
-Happened within first 15 minutes of driving from a cold start..
-Temp switch set to full hot (no change from startup)
-Heat mode moved to various places between full defrost, defrost/floor, floor/dash within first 5 minutes of startup.. (System seemed to adjust to what I wanted it to do in all cases)

Instance #1, Switched to Dash heat, and noticed COLD air.. noticed the temp guage was high (not on H) But higher than usual..
-I adjusted the switches (Temp control and air direction across all settings) after doing this twice, I got a blast of hot air (and I mean HOT, no gradual increase), and the coolant temp guage instantly dropped to what it should be.. Temp outside was about 20 degrees.. Started from a cold start after 8 hrs in the garage.

After it resolved itself, drove to work normally (15 miles - 60mph) normal heat, normal coolant temp..

Instance #2 (today) Leaving work in the morning (outside in 20deg for 8hrs), outside temp about 30deg at the time. Had defrost on and didn't notice the cold air.. Check guage light came on, Temp on high.. Adjusted *****, Burst of hot air, temp dropped back down.. (Also this time suspected temp dropped after adjusting things whether it was on hot or cold temp setting..i.e. Temp didn't rise again with cabin temp control on cold) Drove 40 miles at 60-70mph.. normal heat normal temp..

Took it to the Ford delership this morning where I usually get work done.. They said they were able to reproduce the problem and claim it's the thermostat ($205).. They also said coolant was low.. (which was odd because I just had the truck serviced 2 weeks ago (checked coolant level) and they did a pressure test on the cooling system today and didn't find any leaks..)

Any other ideas before I spend $205.. I have my suspissions since they admited that the thermostat has nothing to do with the cabin climate system..

Thanks ~Ian

 

Maybe hot coolant isnt getting to the heater core, whatever valve that lets coolant circulate or not circulate through the core could be malfunctioning. On my Ranger its called a heater water diverter valve. Max AC setting closes it, all other settings allow flow such that the hot/cold blend **** can modulate the temp of the air. Not sure if yours is similar or not.

 

Just got my 2001 so I'm not sure if it has a valve in the heater hose or not, if so, could be like bcjim says. Also, is the antifreeze OK? If you're getting ice in the system, it could do the things you describe. Finally, are you sure the blend door is behaving. There is (or was) as sticky on this forum abour fixing the blend door in Generation 2 Explorers. And finally, $205 is outragous for a thermostat. Unless the SOHC is much more difficult than the pushrod engine, it's around an hour job (shadetree) and a $20 part.

 

That's not entirely true. If the thermostat is stuck open, the coolant may not get hot enough to provide adequate heat to the cabin. This happened to me, and a new thermostat (about $15-$20 and less than an hour's work, like Jerry said) got the cabin nice and toasty warm again. But since your temp gauge is moving between cold and hot, the thermostat is less likely to be the cause.

From the symptoms you described, I'd suspect the blend door - a common problem with Explorers. For a repair procedure, go to http://www.blenddoorfix.netfirms.com/. I would remove the actuator as described in the procedure, and inspect the hole that the actuator pin fits into. If the blend door is OK, you might have a faulty vacuum motor or heater control valve - or their counterparts, if the '01 models don't have these components. You could also have crud in your coolant or heater core. When did you last flush the cooling system?

Good luck!

 

coolant circulates thru the heater core all the time. there is a door that takes cool outside air and warm air from the heater core and mixes it to the right temp. if you get a "blast" of hot air when you wiggle the temp ****, then it is probably the blend door or its controls. the **** is a resistor that varies the voltage to a motor and moves the door. i would check the **** first and see that it is tight on the rotating shaft and not slipping. in either case, it appears moving the **** back and forth causes the heat to flow. either the **** is loose, or the motor/ door is sticking.

 

I disagree. My blend door failed, as did many peoples, but I can still get AC by using max ac. In this setting hot coolant must not flow to the core since the recirculated air still passes through the core thanks to the broken blend door, yet still enters the cabin cool. In regular AC, one gets hot air with a broken blend door. Also, if what you say is true, why is there such a thing as the heater water diverter valve?

 

Sorry for the hi-jack...but Mr. Hanky lives!!!!

 

Yes, he does...and thanks for noticing!