I usually post in the 73-79 F-series or super duty forum but, I have a question for the guys in this forum this time. My brother-in-law has a 97 F-150 with 4.6L that has no heat in the cab (blows cold air no matter what setting at HVAC controller). Heater core was replaced one year ago and T-stat was replaced last night. Coolant level is full and the heater hoses are BOTH hot so I believe warm coolant is flowing through the heater core. I am thinking that the HVAC controller may be at fault or maybe the mixing door in the HVAC plennum is malfunctioning. I have 97 ranger that had a broken hinge pin for the mixing door inside the plennum (common problem with these trucks), maybe this is the same issue (I don't know). I am wondering if anyone has had this happen with thier F-150 and maybe could point me in the right direction before I take the whole dash out to see what the trouble is. Any and all help will be greatly appreciated. Thanks, -Ed

 

Check in the following as I just had the same issue. Check the switch and blend door actuator, the last and hope it is not a broken blend door. The switch can be worn on the copper and contact, the actuator can be stripped on the gears, the blend door may be cracked at the actuator (common) or completely broken as it is brittle plastic. Unfortunately mine was the blend door inside the plenum and took a day to remove and replace but was only $20.75 with the new aluminum collar reinforced part. Saved over $1500.00 from going to Ford.

 

Now, as I am not so familiar with these model year trucks could you tell me where the actuator is located under the dash. I am assuming it is operated by electric and not vacuum, from you post (The switch can be worn on the copper and contact). I am hoping it's not the blend door thats broken, that was the problem on my 97 ranger and I really do have the time or the "want" to remove his dash. Thanks again, -Ed

 

read some ideas on the blend door, and the selector **** slipping on the shaft

https://www.ford-trucks.com/forums/9...h-a-twist.html

 

Thanks for the additional idea's. My brother-in-law is bringing the truck back to me today so I can check these problem areas and maybe get him some heat again. It's been pretty darn cold here in Michigan the last few days and he has to drive 35 miles to and from work with no heat. I'll let you know what we find later. Thanks again, -Ed

 

mixing "blend door" is above transmission hump, under the plastic dash panel. remove the plastic panel. move heat **** from cold to hot. if it dont go, or stuck/ broke, push it to hot and tie wire it there for now. make sure the hot/ cold **** is not slipping on the shaft.

 

My truck does the same thing sometimes I can Hear the "thump" at higher speeds then I'll have Heat. It will do the same thing when I'm running A/C and I don't want heat.

 

Sorry for the delay but, my brother-in-law has not brought the truck back to me to check it out yet. Still driving around with no heat in Michigan I guess. If he does bring it back I will let you know what we find. -Ed

 

The answer to not stripping the gears on those blend doors in the Explorer's, Ranger's, Expedition's and F-150's is to not turn the hot/cold selector all the way either way. Just always back it off a little, Ford had it a little off on the limit switch and the door will open all the way and try to go a little more or vice versa will close and still try to go more. Just ALWAYS back it off a little, easy fix compared to removing whole dash.

 

my 97 had same problem no heat I checked everything mine was the waterpump truck wouldn't over heat or anything but got curious so took it off and the fan blades on the water pump was completely rusted gone.