Truck is 2020 F150 302A with Tow mirrors.
Mirrors have power heated glass, puddle lights, and turn signals. Manual fold and manual extend.

Smashed the passenger mirror on part of a fence hanging out of a construction site. That took out the signal light lens, and teh convex glass, and over time, the power adjust on the flat glass stopped working too.

Bought those knock-off chinese replacements online. This model: VEVOR Towing Mirrors, Left & Right Pair Set for 2015-2018 Ford F150, Power Heated with Signal Light & Puddle Light, Plane & Convex Glass, Manual Controlling Telescoping Folding, Heating Defrost, Black
I knew they had a visual difference, but figured they were cheap enough.
So sure thing, there was 1 less pin on the connector. Looks like that pin is for the temperature sensor. All the lights and glass adjustments work.

So, what does the truck use that exterior temperature sensor for anyway? Can I just run without it?

 

It’s the ambient air temp sensor. Not only does it give you an outside temp reading, I believe that it also helps regulate the HVAC and air/fuel mixture.

 

I also believe the outdoor air sensor feeds input to electronic modules for engine and hvac performance. Is there a chance to rig a sensor to the mirror, connect to the wire that is available? Maybe even tie to the wire elsewhere, behind a fender etc?

 

@seventyseven250 Don't know if it would work, but I have a sensor I could likely remove from a smashed right side mirror, the small ones.

 

Truck threw a code last night, check engine light is on, I'm sure this is the reason. I may take apart the old mirror and see if I can rig up the sensor into the new mirror. That's a pain, because I'll have to cut the wires inside the mirror to do this.
I see Ford sells the sensor as it's own part too, if anyone was wondering.

 

Thanks @johnday , I'll use the sensor I have and see how that goes.

 

10/4, let us know how it goes.

 

Hadn't thought about it, but the Auto-start-stop doesn't work when the Check engine light is on, so that's one way to disable that.... lol.
I should have time to deal with it this week. Will update everyone.

 

More going on with that Sensor than you know about. It's wired direct to the PCM board through the harness. When in fault, sets the code.
Upon cold starts over a wide ambient outside Temp range,, this Sensor reading is compared to the T-Sensor part of the Map Sensor inside the intake manifold.
The cold readings have to be within reasonable agreement to set Fuel table richness for cold starting. There are two cold start tables that depend in the Ambient for which one selected. If in fault cold starts could become an issue in Winter.
On Hot re-starts, there will be an expected difference between Ambient and Map-T reading. for program control on how to set Fuel , Ignition and Idle levels.
Bottom line it has a lot of importance and may be used by other related functions..
Mount it as the original was, not all inside the Housing for convenience. Temp detection mis-mounted, it's not accurate for the system use.
Good luck.

 

Yeah, I don't plan to run without it. Will get it set up. the 2018 mirrors I bought don't have same mounting point, or more importantly, the internal wiring to get back to the truck door. So I'll need to connect to the truck wiring in the door and to wherever that sensor ends up. Been a busy week so I don't know when I'll have time to wrap this up.

 

For 2018, it depends on the build date as to where the sensor is located.
I have a 2018 and no sensor in the Mirror to my surprise when I looked for it.
If you connect a Sensor in the mirror, mount it in the same position as the old because if left lay inside the housing, the accumulated heat inside a Black container will register as higher temp, when it should not.
Good luck.

 

So little update and some pics. Some of this has been mentioned above by myself or others, but it's worth typing it out again to be clear if anyone else runs into this.

1) you need this temp sensor, as the truck throws a "check engine light" without it.
2) the best and easiest thing is to buy the correct mirrors with all the correct features. I didn't do that, so I had to mess around to make it work.
3) the comment from @bluegrass_7 above is right, if you put the sensor in an area with no airflow, the heat builds up and you have an erroneously high reading, which makes the truck engine fan freak out, which isn't great for those warm sunny days.

So here's what I did:
I needed to map out the wires in the various connectors to see which wires i needed to tap for this sensor.
The Cab-side connector had 14 wires. The OEM 2020 ford mirrors had 12 wires, and the VEVOR branded 2018 mirrors had 10 wires. It was important to map these out carefully, and of course the wires are mostly wrapped up and short and hard to see. And of course, the factory cab-side wire colors DO NOT match the factory mirror wire colors. Not even close. So you can't just match up wire colors, you really need to know the positions.

For added enjoyment, the sensor itself has two unmarked black wires that are indistinguishable. I thought probably that would mean I could connect the wires in either order, but I wasn't taking that change. after the connector from the sensor to the mirror, the wires DO have a color coding, so I snipped it off above that connector so I had colors to work with. This means one extra step if I ever try to put the original mirrors back on.




Here's my wire map.


So now that I figured out which two wires in the cab-side bundle are unused, and which 2 match up with the 2 in my sensor, I use t-tap connectors to splice in some spare yellow wire I had laying around. I needed significant extra length for the sensor.


Note, t-tap connectors are not very popular for Exterior or engine bay wiring. There are other options. I felt okay about it for this case because the connection is on the inside of the door, so it's a dry and protected environment. You can make your own choices for that.

Then test-plugged it in, and hey, everything worked. I had a reasonable reading on the truck infotainment screen. Nice. Time to tuck things away and finally be done.
Nope, on my very next drive, I realized I had no signal lights in that mirror. WTH? Turns out, I folded over one of the pins in the connector, so it wouldn't seat properly. That's the kind of thing that happens to me any time I touch plastic connectors. Somehow I always mangle them. But luckily this could be straightened carefully with need nose pliers and it worked again. Only weird thing, I could not get the connector to "snap" together. Just couldn't. I don't know what I messed up, but it was never clicking. So I used some tiny zip-ties to hold it together so it doesn't work it way loose again.



Got everything together, all works, all good.

A few notes, I don't know the best place to locate that sensor. If you could get it out to the underside of that convex mirror area exposed to outside air, that's clearly best, as it's shaded from the sun. I did run it for a while just near the door, but that spot gets heat soaked and the truck thinks it's 50c (122f) and that's not good. I'm experimenting with locations still. It'll be winter soon enough, lol.

 

You did a great job of hashing it all out.
The aftermarket does not know all the versions and running production changes that may occur over time or all the ramifications of why a change was made.
The CHT Sensor shares a Ground with other circuits.
If this Sensor or its circuit becomes faulty, could cause extended Winter cold temps extended cranking time to starting if the comparison done with the Map, CHT and other references is not within limits because it determines what Fuel Table to use for these low temp. starts, or higher temps starts. To expand on the Fuel Tables, it controls the uses of Direct injection and Port injection on a >percentage basis<. Cold and warm starts preference is high % Port injection for best atomization until the engine warms., then general power and other emissions considerations are in play with a change over to a different table and % of use. A lot of very important overall considerations going on at any given time.
If that ground goes intermittent, other circuits can be affected and present diagnostic decisions that may not work out until this is discovered.
Good work.
Good luck.

 

Small update. While I was parked this week, my drivers mirror got smacked and destroyed. But luckily it was those cheapo VEVOR mirrors, and I had the intact ford factor mirror for the drivers side, so I swapped that back and it's good as new. Now the two sides don't match, which is janky, but whatever, I'll live with it like this for a while.





The drivers side doesn't have the issue with a temperature sensor, so it's a direct swap with no messing about. Just 4 10mm bolts. Very quick.

 

A little bit of a Vincent van Gogh look eh (one ear cut off)? That's a shame. A couple of the dings on my F150 have been courtesy of people bumping carts and/or vehicles into me while I was in the store. Insurance doesn't usually cover those kinds of things.