Climate control either hot or cold, no in between

[Timmmo57]

Is this normal? I have the auto climate control in my 2018 but only use it manually. It seems like no matter what temperature I set it to, the air coming out of the vent is really hot or really cool/cold. It's like there is a magic temperature (depending on ambient/cabin temp) that the controls the switching point between hot or cold air. Like say I set the temp to 73 or less, it blows cool, but once I set it to 74 or more, its super hot. (i'm just using these particular temp numbers as an example to explain the temperature extremes). Is it normal for it too work this way? No way to blend the air temp to just warm, or somewhere in between very hot/cold air temperature? I don't recall my previous 2014 Fiesta doing this but that was some years ago. Thanks.

 

[Timmmo57]

Anyone? The hot/cold blend door actuator seems to be working from a visual inspection. Maybe the cabin temp sensor? Seems strange that I cant get just "warm" air. And its not a matter of "it's only cold on max cold, and hot all the other times". there just is not a "middle of the road" temp and the "switching point" temp depends on the ambient temp. Thanks for any suggestions or input.

 

[Snrub]

I noticed something similar before my blend door actuator failed.

 

[madhatter]

temp sensor. it's a little blue wand that is in the passenger side footwell side of the center console stack. takes about 5 min to replace and cost <$20 if my memory serves. had this problem myself on my '14 and it fixed it.
quick google for the part number:
The part number for the secondary cabin air temperature sensor (the blue sensor located in the passenger footwell on a Ford Fiesta ST with automatic climate control) is BM5Z-19C734-A.

 

[Timmmo57]

temp sensor. it's a little blue wand that is in the passenger side footwell side of the center console stack. takes about 5 min to replace and cost <$20 if my memory serves. had this problem myself on my '14 and it fixed it.
quick google for the part number:
The part number for the secondary cabin air temperature sensor (the blue sensor located in the passenger footwell on a Ford Fiesta ST with automatic climate control) is BM5Z-19C734-A.

The part # you gave me is for the auto climate control cabin temp sensor, but it's not the blue one that goes in the passenger footwell. It's the round one that is mounted behind the dash to the right of the steering wheel (see pic below). The sensor you mentioned being in the passenger footwell is something else i guess.

 

[madhatter]

ew. not the right one. AI fail. sorry. you want the blue one. i can't find in my records what i ordered. its the size of a q tip and blue.

 

[Timmmo57]

Rockauto lists that as both an A/C refrigerant temp sensor and also as a heater core temp sensor??? Both are blue and look identical.

 

[Timmmo57]

OK... so I found out that the cabin temp sensor behind the little "vent" port on the drivers side was completely dislodged from where its supposed to be in its socket so I put it back in. Maybe just me, but it *seems* like it made a slight difference. I unplugged both the cabin temp sensor and the blue one on the passenger side and I did not notice any change in the air coming from the vents. I put a thermocouple in the vent and I found that at the LO temp setting (btw, I never use AUTO, this is on MANUAL mode), the air doesn't come out less than about 80 F without the A/C. (it's 60 F degrees outside). At a temp setting of 81 F, the vent air temp is about 89 F. At a setting of 82 F, the temp increased to 96 F. At a setting of 83 the vent air temp jumped to 120 F. Maybe the temp blend door actuator is an issue or the air temp setting is just very sensitive to begin with from the factory... I dunno. Do those temp sensors only work for the AUTO setting or manual operation also?