Hi I'm new to this site but have read a lot of threads on heating and blend door. I have a 97 f150 with 4.6 supercab . I have heat just not real hot. Replaced thermostat twice and still nothing better . So for chits I turned the ac on max ( removed pump last week) and had hot heat but every now and then I d hear a door move but still hot hotter than the normal settings .don't think or hope its the blend door. Motors not factory and vacuum hoses behind battery by firewall kinda hacked together but what I've been able to find looked righ.

 

vacuum hoses and cylinders are to move doors in the ducts to point the air at the defrost, dash or floor. There is one MOTOR operated door under the radio, above the transmission hump. This "blend door" is variable sop you can dial in the exact temp you want in the truck. It blends the cool air that bypasses the heater, with air from the heater core to get the right temp. The vacuum direction doors are OPEN- CLOSE - not variable. TAke the plastic dash off above the transmission hump to get a better view of the motor and drive.

 

https://www.ford-trucks.com/forums/1...-shooting.html

 

Will do tomorrow on the graveyard and just got done with rear brakes . Will it hurt anything running ac max to get the heat

 

well, i really dont understand how the AC on max is getting heat. What "max" does is close another damper so you go no outside air, just recirc the cab air. I assume thats what your getting when you say "better heat"... and no, that will not hurt.

 

Cool I ll check blend door and let it be for now if bad at least till summer thanx.

 

Blend door sounds to be going full to each side and all other doors function right going to use therm gun and try to get temps off everything ? Almost was hoping it was blend door just to know.

 

Another option is the "outside air door" i was talking about. Probalby in front of the glove box. If it leaks bad, you get cold air dumping onto the passenger side floor. When you go to "max AC" the door is suppose to close all the way and recirc inside air. Normally when the door is bad, you get lots of cold air onto the passenger floor.

 

here is a drawing on the ducts and doors

https://www.ford-trucks.com/forums/9...-please-2.html

 

Took temp reading on heads by each exhaust port and have about 250 give or take a few degrees but at thermostat housing and metal pipe at back of motor for heater core about 95 to 105 tops. The radiator is only about 50 or so .. could I be having a pump issue . Whether .the fact of shutter which I need to poke around here a little more I read last night about bad plugs or wires could be a possible added culprit of this also. Sounding almost like full coverage and a joy ride if only .

 

top hose to radiator should be thermostat temp... close to 200 degrees. What does your dash gauge say for temp ? Feel the heater hoses. One should be HOT inlet and the out should be quite a bit cooler after you transfer heat to the air. If water pump or fan dont work, you sould eventually overheat... again, look at dash guage.

 

Dash guage is about 3/8 up normal top hose temp only about 90 95. Temp at heads by each exhaust port about 250 lower thermostat housing about 120 . Dash gauge does rise up from cold don't believe its broke.

 

your original post said you tried the thermostat twice... but now you say the output of the thermostat to the radiator is 90 degrees ?? Something is wrong here.

 

Yea has me stumped the rubber shouldn't make that much of an insulated difference in temp.going to take temps again when I get home in morning and see exacts on .

 

Found water pump has excess play going to replace this weekend just dealing with a lot of issues with truck since I loaned it to father in law for a long trip , from this heat when u need it most , shutter and shake at 40 to 65 ,( plugs hopefully), and noticed no cel today so had codes checked of course p0442 and p0401 . Pretty much believe I'm gonna be through whole vehicle this year.