F-150 thermostat?

[Angry Perch]

2012 F-150
5.0 liter

With heat on hi, vents blow cool at idle, and warm when I bring the RPMs up over 1000 or so.
Thermostat?

[Buckmark]

Could be, could also be low coolant level, poor flow through the heater core etc.
That vehicle may throw a fault code of P0128 coolant temp.
Check heater hoses temp in and out with a heat gun or your hand, if you have access to a scanner check engine coolant temp per scanner and proceed from there.

[jackelope]

2012 F-150
5.0 liter

With heat on hi, vents blow cool at idle, and warm when I bring the RPMs up over 1000 or so.
Thermostat?

On both ends of the dash?

[Angry Perch]

2012 F-150
5.0 liter

With heat on hi, vents blow cool at idle, and warm when I bring the RPMs up over 1000 or so.
Thermostat?

On both ends of the dash?

Yes I think so.

[CP]

I'd just change it.  Cheap part and an easy job.

[skeeter 20i]

can you change the temperature at all by just adjusting the blend knob?  If not then I might suspect the blend door inside the dash. 

[Woodchuck]

can you change the temperature at all by just adjusting the blend knob?  If not then I might suspect the blend door inside the dash.

A far more common issue than thermostat on that truck. 

[Fl0und3rz]

Are they still vacuum actuated in that year?  Vacuum leak?

[Woodchuck]

Are they still vacuum actuated in that year?  Vacuum leak?

Electric, dual zone trucks are even more fun.

[jackelope]

can you change the temperature at all by just adjusting the blend knob?  If not then I might suspect the blend door inside the dash. 

90% of the time it's one side or the other that doesn't work.  That's why I asked. Temperature blend door actuators go bad all the time.

Is the engine temperature behaving normally?

[Buckmark]

can you change the temperature at all by just adjusting the blend knob?  If not then I might suspect the blend door inside the dash. 

90% of the time it's one side or the other that doesn't work.  That's why I asked. Temperature blend door actuators go bad all the time.

Is the engine temperature behaving normally?

Thats why i said to start with some simple diagnostics
1) Engine coolant temp per pcm - if it is normal say 195 good, (easy check) next step
2) coolant hoses in and out of core, hot in and cold out? restriction in core, hot in and still hottish or very warm out, core is good for flow (easy check) next step
3) getting a little harder as now you are looking at possible air inlet door and or actuator, the blend doors on the vehicle show a right and left, so if it is even on both sides may then be inlet problem, etc etc....

Start at the basics, coolant temp, coolant flow then make it harder 

[Bean Counter]

I'd just change it.  Cheap part and an easy job.

 

[Angry Perch]

Thanks for all the input. i'll start looking into it tonight. I can sit at idle, and the vent blows cold. I rev to 1000+ RPM, and it goes warm. back to idle, and blows cool again. Temperature adjustment (blend) works as it should as long as RPMs are up.

[jackelope]

I'd just change it.  Cheap part and an easy job.

 

Sure. Just change it. Spend your 2 hours and your money and when it's not fixed, throw some more parts at it that don't fix it.
The blend door actuator actually takes less time than the thermostat to change and the part is likely cheaper. Just FYI.

[jackelope]

I'd just change it.  Cheap part and an easy job.

 

Sure. Just change it. Spend your 2 hours and your money and when it's not fixed, throw some more parts at it that don't fix it.
The blend door actuator actually takes less time than the thermostat to change and the part is likely cheaper. Just FYI.

Nevermind. The t-stat pays 1.1 and the right side actuator that goes bad commonly pays 1.4 hours.
But...why diagnose anything when you can just throw parts at stuff.