I have a 2013 F150 Platinum and occasionally the air will stop blowing cold and only the fans seem to be working. If I look at the outside temperature, it says it's -40 (Yep, NEGATIVE 40). This will last for only a few minutes and then the temp reading will slowly start to raise to a normal reading. Once that happens, the AC will kick back in and everything seems to be fine. I've now had this happen 4 times in the past 3 weeks.

Anyone have any ideas? Could it just be the ambient temperature sensor is going bad?

 

I don't think the outside temp indicator has any bearing on the ac....it's not on a thermostat that would kick compressor on and off.... it's on or its not unless the higher trims have different system than my xlt

 

I will have to say, that I think the outside temp display does affect the A/C. Here are two observations that led me to this conclusion. First, I don't like to run the A/C on max or recirculate unless I really need to. Every time the outside temperature reading climbs to 75, it will turn the recirculate back on. Every single time! I pull out of the driveway and the temp says 73 for instance. As I get on the open road where its warmer, as soon as it gets to 75, it turns the system to recirculate. Next, if the temperature is in the 90's when I get in the truck, when I start the truck the in-truck display temp will say way more than the actual temp until I get moving. It will say like 105 or so (my truck is black). As soon as I start the truck, the engine/condenser cooling fans turn on full blast; such that it sounds like a jet engine under the hood. Once I get moving and the temperature reading drops, the fans drop to normal speed. If I start the truck in milder temps like 80 for instance, the cooling fans start, but at a normal speed.

Furthermore, most manufacturers disable the compressor at very low outside temperatures. It will damage the a/c system if it tries to operate at like 5 degrees for instance.

The computer may very well use the same sensor for this as the in-truck temperature display.

That's just me connecting up some dots; so I could be wrong. However, I am very sure of my observations about my truck's a/c responding to the in-truck temperature display.

 

I always run it on recirculate and as far as I can remember running max ac automatically puts it on recirculate. I'll have to test it out tomorrow and see if mine does as yours. I've always argued with people who'd give me grief for having car windows down and running ac that unlike in your home which has a thermostat to regulate air temp in an automobile it's just simply on. Maybe newer modern stuff is different I'm sure it probably is in the luxury auto market.

 

You make very valid points. But what if there's another sensor controlling the HVAC system that's located elsewhere on the truck and it just happens to be reading accurately like the one that feeds the display on the dash?

It's a possibility I guess. Would be nice if somebody with a service manual could look at the schematic and see exactly where the sensor near the grille of the truck actually terminates, or perhaps the dealership has tools that can tell you whether or not the sensor by the grille of the truck is the one used to make calculations for the operation of the HVAC system.

In any case, if yours is showing odd readings on the display, I'd start with a new sensor since that should be simple and cheap. If that doesn't solve it, you'll need to try a reflash of the ECU after checking the wiring to make sure it's not damaged near the sensor.

 

I know I'm in the wrong decade with my observations but I notice a difference in temperature settings based on information from the light sensor on the dash. In other words, set point of 75 is fine in sunny conditions but not so much if it's cloudy or dark outside. Just my observations on my vehicle.

 

Others have said that this sensor is called the "sun load sensor" and it is in fact used for lots of purposes in the truck, one of which is controlling HVAC output.

We're basically driving computers on wheels today. I'm glad I'm old enough to remember the simple days.

 

Me too but I'm also glad I'm not driving without all the features that comes with it. That kind of stuff is neat how works.

 

I presumed that since his (Kingrl2) a/c only acts up when the in-truck display is giving whacked-out readings, that it is likely the same sensor. I feel it's unlikely that 2 temperature sensors failed at the same time.

Who knows though. This is all just observations and conjecture on my part.

 

I too have an issue like this. I believe the two are directly related. Mine reads 50° all the time. A new sensor was 15 dollars so I went ahead and replaced it. No change however. Still reads 50. So I am thinking I have some bad terminal in plugs or some chafed wires shorting...

 

I have a 2012 f250. It says -40 at start up. Every time. The longer it runs the temp goes up to where it should be. Shut it off and it starts all over. It is winter now and the air seems to work, but I don't know for sure. I am wondering if this is going to be a problem when it gets hot?

 

If the sender is saying it's too cold out the compressor will not run, so yes it could end up being a problem.