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.

 

[isis]

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

Where is that first one? I have an intermittent problem and only knew about the second one.

 

[rallyrabbit]

Where is that first one? I have an intermittent problem and only knew about the second one.

the temp sensor is on the side of the box assembly, this is the one in the way when you change the cabin filter.

the in car sensor is behind the controls, also attached the the box. One of them is supposed to be blend temperature and one is supposed to be cabin air temperature (the one behind the controls, i think, is the cabin temperature).

 

[SVTBob]

Might it be the passenger side actuator ?

 

[isis]

the temp sensor is on the side of the box assembly, this is the one in the way when you change the cabin filter.

the in car sensor is behind the controls, also attached the the box. One of them is supposed to be blend temperature and one is supposed to be cabin air temperature (the one behind the controls, i think, is the cabin temperature).

You are correct about the cabin air temperature one. I wasn’t even aware of the other one and haven’t had the car long enough to get to the cabin filter. Thanks for the info, maybe changing that one will help me out. I did the other one and the clicky blend door on the passenger side and it still acts up sometimes. Usually if I cold start the car everything works fine but if I shut it off to run into a store, when I come back it decides to pump cold a/c at any temperature setting below 80 degrees.

 

[rallyrabbit]

Well, I even found another one....

Temp Sensor
CV6Z-19C734-A

RallyRabbit: Can't find where this one goes yet..... This is a white sensor. Ideas?

In Car Temp Sensor
3M5Z-19C734-C

RallyRabbit: This sensor made a difference. On ST, you get to this by removing bottom steering column cover and it is to the right, remove it (mine was GUNKED up) and clean the vent on the dashboard.

Filter Box/Evap Box Temp Sensor
BE8Z-19C734-A

RallyRabbit: This goes in the evap box behind the cabin air filter. Replaced this, it is cheap, didn't make a difference. Apparently this one going bad keeps the A/C from functioning.