Blowing Nothing but Hot Air unless on 60 Degress

[rallyrabbit]

Weird problem that just started happening today. It's been really cold for 2 weeks and heat and adjuster has been working great. Today, a warmer day, I started having the same problem on 3 drives:
1) Set to Climate Control to Auto and 68 degrees: Blows nothing but HOT air
2) Set to Auto and 80: Blows nothing but HOT air
3) Set to 60: Blows fully cold air (can hear the blend box actuator moving but no clicking)
4) Set to 61, stays cool for a second and goes fully hot again

It's almost like 60 is a "fully open" or fully closed setting for the blend box flapper, and everything else is thinking it is too cold and needs to be hot.

Thing the temperature sensor in the blend box is bad?

 

[isis]

Temperature sensor is by your right knee, not in the blend door. It’s not hard to get to from under the steering wheel. YouTube it.

 

[rallyrabbit]

I appreciate the answer, but that isn't really what I am asking. I know replacement is easy of the temp sensor in the system. I'm asking for thoughts on whether the climate control temp sensor or the in car sensor is bad:

Temp Sensor
CV6Z-19C734-A

In Car
3M5Z-19C734-C

 

[Intuit]

We've seen missing teeth in the cog for one of the blend door actuators.

Picked up a lighted USB-C bore cam from Amazon for cheap.

I'd watch/listenTo the temperature blend door and verify that it's moving like it should. The three doors MIGHT be cycled through full range during power on/off self test? (power off is on a ten or fifteen minute delay)

Check for climate system codes.. With multiple temp sensors, a sensor fault should be easily identified on consecutive cold starts by comparing the readings during POST. Disconnected/shorted sensor should be easily flagged by BCM test as well.

I'd also wonder whether the sensor output can be read via ForScan?

 

[rallyrabbit]

I'd also wonder whether the sensor output can be read via ForScan?

Just went over to my brother in law's shop to test that, sensor shows -40c, so I think it is the problem. Thanks for the sounding board here

 

[Intuit]

That's pretty damned cold.
But why does it only not blow hot when set to 60F as opposed to 61F?
There is an 85F (IIRC) and a "Hi". Is there a 60F and a "Lo" ?

Regarding that specific number...

...it appears that specific number is THE number at which both C and F are the same...


...so that makes me wonder, what does the climate system read for a disconnected sensor?

 

[rallyrabbit]

I think the lowest setting being 60 degrees defaults to heating blend door closed and go full a/c. Just like the top hot setting goes full open for blend door. At least my testing shows this to be the case.