Recon1342
Recon1342 SuperDork
11/28/23 6:56 p.m.

1997 F-150, 4.6L V-8. 
 

No heat. At all. Zero. 
 

Replaced thermostat, no change.

The heat/cold control knob feels like it is spinning freely and not moving anything. I don't know if there's a busted linkage, or what. Anybody have any ideas?

02Pilot
02Pilot PowerDork
11/28/23 7:35 p.m.

No specific knowledge of what's in charge of sending the heat to the cabin on an F-150, but the first thing that comes to mind is a broken cable to the heater valve.

Edit: Looks like it might be vacuum controlled on these.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
11/28/23 7:44 p.m.

It's a servo module on these.  Common problem is that they die.  Other common problem is a clogged heater core.  Actuator replacement is pretty easy.  Heater core is a complete dash removal.

This video shows the actuator replacement.

 

Laserface
Laserface New Reader
11/28/23 10:42 p.m.

The knobs on those won't have much resistance, so that doesn't tell you anything.

Are both heater hoses hot? My vote is plugged heater core. How grody is the coolant?

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