such wonderful reading material! LOL
Honestly it was helpful. You had mentioned something about the "logic" of the hack and after reading the article I got to thinking that maybe if the computer was seeing a 73 degree evap temp it may throw off its logic and start doing wacky things....so I did looked at that temp/resistance chart ans saw that a resistance between 58k and 95k would yeild a temp between 50 and 32 degrees. Fortunately the kit of resistors I bought from Amazon was a variety pack! I dug out a 75K resistor and put it in to see results. well now the EVAP temp is reading a steady 41 degrees! You reported your reading was approx 40 so I felt pretty good.




I thought it was odd that the AC pressure keeps going high but I have wrapped my head around that it is basically how the computer forces the compressor to shut down. Interestingly I noticed that once I changed the resistance level to 75K, when the pressure would go high the EVAC% (which is the AC compressor load percent) would drop, incrementally 50,35,22,6 then start rising incrementally. with the broken evap sensor and the first resistor, I recall that it would just drop to 0, then eventually pop back to 100. So I felt like I was making progress because to me it looked like the AC compressor was now operating at a VARIABLE rate.
Note in this next pic 1 minute later the EVACC_DERATE changes to driver WOT (which I think the WOT is just a bad read by forscan, but it is detecting that the computer is giving a command) the percent load for the AC compressor has reached 100


I could feel the vents start to chill so I was getting excited...decided a drive was in order so I took off....
then the AC quit! vents started warming again....so as I was driving and puching buttons and selecting max ac then auto then changing temps then....blah blah...I realized that I had no idea what my initial selections were for the AC. I went to MAX and drove on with the windows down. In a couple minutes I felt the vents getting cool, then cold, then warm, then ambient.... GGRRRRR
Thinking through the article and remembering the different sensors that were playing a role in the computers decision I pulled over and swapped cabin temp sensors since I had it with me. Initially I had replaced the sensor but found no change in performance so I put the old sensor back in. I had not returned the new one yet so....


I put it back in. For those following along at home, this is where it goes and what it looks like. its right behind a little trim piece with air slots...pretty easy to get to, just take the panel off under the steering wheel and gently pop the clips.
Started driving the vehicle again, noticed the DTC for cabin temp and cabin humidity sensor had appeared. reset code as I knew it was because I disconnected it and reinstalled.
driving down the road vents getting cool, then cold...cabin getting cold...feels great...
here is data after 15 min of driving

wow 36 degrees out of the vent!!!
so I am doing the happy dance right?? well no.
Continued to drive and as I slowed down from a steady 45 on country roads to a stop and go 30, the cabin got warmer and warmer. AC would cycle on then off...vents would get cool about 65 degrees, then warm back up to just about ambient....
frustrated I drove back home. as I was driving vents got COLD and it was comfortable again.



So I did the stop and go driving again and there was no problem. Blew cold the whole time...no issues.
If you look at the Ambient temp readings you will see that it dropped. Somehow this ambient reading, the cabin reading, the sun load, maybe even more things, are incorporated in the computers decision.

I think that is having an affect on when the computer calls for AC. If the driver calls for AC, then the computer looks to the ambient, then the evap temp and seeing that it is 41 probably thinks, well I dont need to call for more compressor because the evap is right where it needs to be for this ambient. but its really not. So it blows air thinking it would be 41, when its actually 65 and then the cabin heats up until it is to a point where the cabin sensor shows its warm, then the computer says WOW 41 degree evap is not cutting it we need less than that and it starts to crank the AC compressor.
It might be with higher ambient temps the computer decides more often that the 41 degree evap is just fine and there is no need for the AC compressor to run, so it shuts it off...I dont know really, just speculating. but with a lower ambient it need the evap colder to reduce cabin temp, because there is less differential between the evap and the ambient, so it calls for more cold?

Anyhow I called it a night. Next day I had a 2 hour drive to a baseball game. temps were in the mid to upper 80s. AC was glorious. I was seeing vent temps less than 45 degrees most of the trip. At one point it froze on the way home...28 degree vents. That was mostly 40-60 MPH. when I got into town, AC was cycling again. on off, warm, cool, hot. But it worked on the way home after we got going.

Next day my wife drive an hour and she had the fan on way low...ambient in the mid 70s...froze up (as I would have expected)...she did not know that I would have had her cycle the AC switch because she was at a lower blower speed...but on her way home, on the highway, low 90 ambient, it was cycling cool, warm, cool, warm...If you ask her she says that she had it set EXACTLY as i told her and it just did not work...I dont know...
I took it out for a drive and ambient was 93 and sure enough warm, cool, warm, cool out of the vent 65.
But when the ambient dropped a couple degrees boom cold air out of the vent.

this morning after the car sat all night I went out to get a reading on all the temp sensors like the article stated. Vehicle off. here are the readings:


Do you think anything is way out of whack or needs to be replaced?

then I drove to town and back and I had mid thirties air out the vent with an ambient of 75.




So I know that this is a long write up, but I am hoping that it is helpful for someone with the same issues. Also I would like to finish this and have a solution!

Do you think the temp readings are close enough or do you think a sensor is bad?
I am going to leave in the "new" cabin sensor thinking that the old may have been intermittently working....
Maybe I will replace the AC pressure transducer/switch thingy again and check the reading against the gauges to see if another one is more accurate...maybe I had a dud.
I would guess that the "solution" at this point is replace the evaporator? and then see if it works?

instead of replacing the evaporator for a $20 evap temp sensor....I wonder if....because that evap sensor plug is so easy to get to in the taurus...if there is a temp sensor that would plug into it????? Any temp sensor would do as long as it fit....then I could stick the sensor in the floor vent located at the drivers feet....that would at least give a variable temp reading that was somewhat close to the temp of the evaporator.
Also this might be a good diagnostic to determine if the evaporator/temp sensor replacement would fix the situation.
Any thoughts???

 

I am looking at a part YH1735




it is a evaporator temperature sensor off a Ford… Looks like F series pick up…. Of course no one has a local one in stock so I got to order one. Amazon has it 25 bucks.
do you think it will click into my existing connector? I’m thinking to just stuff it in the floor vent next to the drivers feet. It will get a temperature that is closer to the evaporator and it will vary so that should help the computer adjust more accurately than given the static resistor reading.
The connector on my vehicle looks like this:



The female connector on the YH1735 looks like this:


is there anyway to confirm that they are the same connectors? Do you think it will work? What’s your opinion?

 

That sensor is for a range of the Super Duty models from the mid-teens.

The corresponding pigtail is the WPT-965. My 2020 pigtail guide shows that the Taurus uses that same pigtail for models up through 2017... I don't know if they simply didn't update the catalog for that entry since then as they show no data for that connector for that model for subsequent years.

My gut feeling is that it will plug right in but I can't find documentation that would explicitly support that. The connector shell diagrams for that connector in the EVTM for the 2016 F350 and the 2018 Taurus appear to be identical.

Be interesting to see how this progresses..

 

Well they say that education cost money…
this I can afford! LOL
part ordered I’ll post back in a couple days after I get it.

I suppose if the connector does not fit I could always cut the connector off and jam the wires in to see if it works

 

I just got the parts in. I have not had a chance to mess with the vehicle, packing up for an unexpected trip. I will have to check back next week…

 

All right... I received this part:



As well as a pressure sensor:


I tested and found that the pressure sensor that was in the vehicle was still showing +30 PSI via FORSCAN vs the gauges. Replaced the pressure switch and now FORSCAN shows 10 PSI higher than the gauge. I figure this is better than 30PSI so I am keeping the new pressure transducer thingy.

So the moment of truth arrives....and I WAS ABLE to plug in the evap sensor directly to the connector!!!
Problem is that it must be a different resistance....it is showing 183 degrees with a vent temp of 60 on my probe... GGGGRRRRRR
I was able to plug it in, and tuck it right in the foot vent above the accelerator as I hoped.




After driving around for 10 min or so watching the evap temp through forscan, it only dropped to about 175 degrees while my manual probe was showing approx 50 degrees.

I disconnected the new sensor and HVAC threw an error as expected...my resistor inserted again...41 degrees. error clear. Insert the evap part, no error so it must have good connection...but again showing 165 degrees....the temp probe on the part is cold to touch and manual probe shows 48 degrees.
so in theory the fix CAN work...I just need a evap sensor that has the same resistance range as the one the taurus is expecting to see.
Are you able to check the resistance of other ford evap sensors vs the one I purchased (YH1735)? I will see if I can find a different part number and edit shortly...

ok I see a Motorcraft YH1662 Air Temperature Sensor...
or this one...
I might think this one just from looking at the model years and possibly the connector: Motorcraft A/C Evaporator Temperature Sensor Part # YH1771

what about any other temp sensor that may have a pigtail or may plug directly into the socket??

 

Well, I looked closer at the respective temperature/resistance curves for the Taurus and the '15 F250 sensors. Very different, see below.

The YH1735 sensor, at 80F, is going to measure ~2.4kOhms. The Taurus' PCM is going to correlate that resistance to an evaporator temp of ~180F which matches your test result.

What is needed is a sensor with the same temp/resistance curve as the Taurus uses but available as a plug-in replacement instead of as the whole freakin' evaporator case. If you can locate some other candidates that might plug or splice in, I can check them against what's in the service manual to see if the thermistor is the same or similar enough.

 

ok I see a Motorcraft YH1662 Air Temperature Sensor...
or this one...
I might think this one just from looking at the model years and possibly the connector: Motorcraft A/C Evaporator Temperature Sensor Part # YH1771

 

I was just going to post that the YH1662 has the correct response curve (but the wrong connector - splicing would be required). Used on the 06-12 Fusion/Zephyr/MKZ/Milan per Buyer's Guide.

YH1771 is a no-go, it appears to be the same as the YH1735's curve.

 

OK i will order the YH1662
I would like to order the pigtail for the Taurus side I think you said it was pigtail is the WPT-965? needs to be the female, same as we have on the F250 evap part yh1735. here is the pic of what I want:



then I want to order a pigtail for the sensor side of the YH1662 would that be this???
Standard Motor Products HP3840 handypack Air Charge Temperature Sensor Connector Assorted, One Size
https://a.co/d/as0dqyg

then I am guessing I can just splice the wires off the pigtails together and viola....

Could you please give me good part numbers on those pigtails or amazon links so I get the right stuff?
thank you much!

 

Looks like the wrong connector.

Yes (fingers crossed....).

I'll see if I can locate something. Takes some digging.

 

thanks for checking it out. very curious if this will solve it

 

If the female connection on the taurus side is going to end up being 20 bucks I might as well just cut the pigtail off the yh1735 temperature sensor I have and use that. Problem solved on that end.

so really I just need what looks to be a female….or is it a male…pigtail for the yh1662
when I look up a 2012 fusion under electrical connections in rock auto I do see something maybe it’s HP4400…maybe hp4665. It doesn’t look perfect maybe it fits? Let me know what you can find on your end.

 

I came up empty on a connector that matches the Fusion sensor. I suspect it was only available as part of a harness and I can't locate anything with my limited sources

Have a pick and pull close by? If one has a Fusion, that's the most expedient way of getting the connector (and another sensor, if you wish).

 

OK I finally had a chance to look at the yh-1662. And golly it’s difficult to find a pigtail part that’s going to clip into this. I’ve been to a few parts stores and looked all over the Internet like you did.
But I ended up doing was going to the dealer and telling him I was working on a 2012 fusion, I needed the pigtail for the evaporation temp sensor which I had in hand. I gave him the sensor and package and he looked up the part number and went through all of his different schematics and cross-referenced with all kinds of different things blah blah blah he came up with part 3U2Z14S411CZB which is motorcraft wpt967. He had a couple pictures of it in the computer and it looks like it has an edge that will slide right into the slot on the sensor and it looks like the correct shape. It is called “Sun Load Temperature Sensor Connector”…
Dealer wanted 35 bucks three day delivery, rock auto popped at $25 including shipping…
ordered it from rock auto I will report back once I get it in hand see if it clicks together. I’m just going to cut the connector off the end of that other one and pigtail them together… I’ll report back shortly.