Hicksbarry94

I the other day my 99 ford f150 4.6l the heat quit working so I thought is was the thermostat so I went and got a new one replaced it and everything but I still have no heat nothing is leaking I don't smell antifreeze my truck does not run hot what could it possibly be :/

Frank_Ford

First make sure your coolant is topped off. Also, what is the condition of your coolant. If it is real dirty and rusty, something may have gotten plugged up in your system and is blocking or restricting the flow to your heater core. If not that, most likely the blend doors are not working. Usually from a bad vacuum line to the door. First check around the heater control.

When you changed your thermostat, did you put in an 190-195 degree therm. If not you will not get good fuel economy

Good luck

Hicksbarry94

I have the fail safe one and it is at 195 temp so if it is clogged how would I unclog it

jmplants

Check your heater condenser

bchauler

Could be the blend door. Put the heat on and pop the hood. Feel the two hoses that run to the firewall on the passengers side. Are either of them hot? Both?

lzf150

same thing happened to mine.
replaced the thermostat and nothing happened
ended up draining my whole heating core.
it was real dirty.
after draining it and putting in new anifreeze it worked.

Hicksbarry94

Don't the blend door make like a piping sound when it is not working cause it can't open

mduffy1805

Sounds like heater door to me. Had the same thing happen to me. When I replaced it found out th door was broke at the bottom where the motor is.

Hicksbarry94

How do I find out if it is the door or not?

Hicksbarry94

Where is the door located and how do I get to it to check