Hey, I'm new here and I have a question. I have a 2000 F150 V6 and I have been having heating problems, the truck will blow warm (maybe Luke warm) air out of vents (vents only, if I switch to defrost it turns to cool air) when truck is parked, but when i'm driving, it turns to cool air. Also does not blow as hard as the cold air does, my ac works flawlessly and freezes me to death but now it's getting cool here and just noticed my heating problem, any help or advice on what to look at would be much appreciated, thanks.

 

Check your coolant level...

 

check coolant level. make sure temp gauge is reading normal. about 1/3-1/2 up the gauge. After making sure its at proper temp...put it in park...keep the heater running on the panels with the setting on hot and fan on full blast and rev up the motor to about 4000 rpms a few times...you can even hold it around 3500-4000 for a brief time and see if your heat gets hotter. If it does...rev it a few more times and then drive it normal and see it the heat stays hot. Could be a block in the coolant sytem hindering proper pressure and flow...raising rpms will speed water pump and increase pressure. could remove blockage. O and say a prayer...worked for me !

 

If coolant level is normal, changing out your tstat is going to be the next step. How many miles do you have on the truck?

 

Coolant level is fine, truck has 150,000 miles on it.

 

Also check the heater hoses for the heater core at the firewall make sure both get hot..... might have a clogged core...

 

Checked the hoses, the both get warm, one does get warmer than the other, not sure if that's normal or not. Its weird how it gets warm when on panel and truck is just sitting there, if I switch it to defrost it cools, or if Im driving it will blow cool. Kind of stumped on this, probably gonna check tstat next.

 

After driving the truck, check the big water hoses on the engine. If they are NOT too hot to touch, then it is likely the thermostat. Same for touching the radiator. The normal operating temp of engines is about 170-190 (which means the coolant is also that hot) which is too hot to touch for more than a fraction of a second.
I guess it could also be the valve that controls water to the heater core, if it is not the thermostat.

 

I've noticed that it will heat up when revving it up or getting on the gas, still just through panel only, also only one hose going to the heater core is super hot, other is luke warm. Thinking it might be clogged up, Haven't had time to do any work on it, plan on working on it this weekend.

 

I have almost exactly the same thing going on with my 2002 F150 4.6. Standard 3 **** controls. Will only get lukewarm at best and not even that on anything other than the "FLOOR" setting. Highway driving achieves the warmest temp.

Coolant level is fine. New thermostat with no change. Temp. comes up to where it should be according to gauge. Blend door is operating properly. Temperture in the overflow bottle is lukewarm at best. That may be normal I'm not sure???

A couple of questions.
Where is the valve located that controls flow to the heater?. Is this valve simply open/close in normal operation or is the degree of opening regulated somehow?

Truck has over 200K on it with the original water pump. Anyone think possibly that the pump is not moving as much water as it should. No overheating or leakage from the pump.