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S550 sync1 to sync3 upgrade - How I fixed the A/C to be true automated climate control

AUGalos

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Hi everyone,

This is my first post in this forum, hopefully it will be useful for everyone who have upgraded from sync1 to sync3 on S550. My car is a 2015 V6, so having the premium trim that brings sync2/3 was never an option. After a few years of frustrution I bought one of the kits that allows you to swap to the sync3 APIM and FCIM from hellhorse performance. This upgrade also makes your A/C go from manual to climate... well not exactly!

For everyone else out there who has done this, you probably can relate to what I am about to describe: The A/C doesn't work correctly at all times. When the temperature of the vehicle is at the two ends of the spectrum (too cold or too hot) things are working fine because all you need is full blast cold or hot air. But when the temperatures are not extreme, especially during spring and fall, the A/C is unable to regulate the air temperature correctly, and you cannot do it either because the manual controls are gone. After a couple of years of annoyance I decided to try and fix it, and I am happy to report that I did! So here is a guide if you are facing the same problem.

First of all, to explain why this is happening: The premium S550 cars have a dual zone climate-control HVAC. The interior part has nine pieces:
1716331053877-dh.png


One the other hand the manual HVAC of the basic model only has 6 pieces:
1716331227962-zj.png


What we are missing here are the two air discharge temperature sensors (center register (1) + footwell (7)) that give feedback to the system about the discharged air's temperature and the passenger side door actuator that controls the second zone. We are also missing the sunload sensor on the car dashboard that gives feedback of the amount of heat from the sun, this one is not included in this list. Unfortunately there is nothing we can do about the second zone actuator, the HVAC unit is missing the right parts to make it work, so there is no need to try to add it.

This guide will tell you how to install the three missing sensors so the HVAC becomes fully automatic, climate controlled (but not dual zone!).

Let's start with the missing hardware, you will need:

2 x Cabin Air Temperature Sensor: Part #: YH1947 (FL3Z19C734A):

https://parts.ford.com/shop/en/us/ac-repair-parts/cabin-air-temperature-sensor-52l-p-yh1947
1716332038760-j2.jpg


You will also need 2 x connectors for these sensors: Motorcraft Air Charge Temperature Sensor Connector WPT-967, ford calls it C2436 in the manual:

https://ford.oempartsonline.com/oem-parts/ford-wire-assembly-wpt967

1716333423298-5n.png

1716333458958-uf.png

1716333503770-ho.png

1 x Dashboard Sun Load light Control Sensor: DG9T-14A597-B
1716332414836-bt.jpg

https://541motorsports.com/products...ight-sensor-assembly-oem-dg9t-14a597-bc-15-20

You car already has a sensor that looks like this but it doesn't include the two sunload sensors that feed to the HVAC controls, it is only used to detect the ambient light so the car lights can turn on/off automaticaly. One way to distinguish between the two is to check the number of pins. What you have only has 2 pins, what you need has 4 pins. See the following photo of the connector, the black is the old one, the gray is the new one. Their back shape is slightly different (see the second photo) so if you try to plug in the 4-pin sunload to the 2-pin connector it won't fit.
1716332593995-3o.jpg
1716332616552-mr.jpg


So in addition to the sensor, you also need the 4-pin connector: C286 - Sunload Sensor, Pigtail kit part number WPT-1013, Service Part Number: 9U2Z-14S411-TA, Harness 14401:
https://parts.ford.com/shop/en/us/w...d-temperature-sensor-connector-wire-p-wpt1013
1716333621058-op.png

1716332983720-2d.png

1716333051699-4p.png


Finally, you will need the right pins to connect the wires to the connector that goes to the sync3 FCIM. Unfortunately I don't have the right part number for those, I post a photo in case someone has the information and I can add it to the guide. I ended up removing the neccessary cables+pins from used harnesses as I mention later in the guide.
1716333800936-hz.jpg


The sensor cables will terminate on the connector C2402B that plugs in to the FCIM:
1716334037684-cx.png

1716334081918-yh.png

1716334130075-4n.png

1716334164281-n9.png

1716333765718-2j.jpg


The VREF- return voltage needs to terminate on the connector C2402A of the FCIM:
1716334649306-qq.png

1716334678941-05.png

1716334711082-nf.png

1716334749564-wj.png

Here are the wiring diagrams:
1716334424982-2u.png

1716334454582-t3.png



Here is the summary of the connections you need to do:

1. Left Footwell Air Discharge Temperature Sensor:
PIN1 (white cable) -> C2402B: PIN 4 - VH409 (Sensor Discharge Temperature Left)
PIN2 (Gray/blue cable) -> C2402A: PIN 2 - RH111 (VERF- Climate Generic VREF Return)
2. Driver Side Center Air Discharge temperature Sensor:
PIN1 (Gray/blue cable) -> C2402A: PIN 2 - RH111 (VERF- Climate Generic VREF Return)
PIN2 (Gray cable) -> C2402B: PIN 5 - VH410 (Sensor Discharge Temperature Left 2nd)
3. SunLoad Sensor:
PIN1 (Yellow/Orange) -> C2402B: PIN 22 - VH417 (Sensor Sunload Right)
PIN2 (Blue/Brown) -> C2402B: PIN 24 - VF14 (SENSOR - AUTOLAMP DAY/NIGHT (AMBIENT LIGHT+)) === This one is already connected to the existing sensor, must de-pin and re-pin to the new connector
PIN3 (Violet/Gray) -> C2402B: PIN 21 - VH416 (Sensor Sunload Left)
PIN4 (Gray/Brown) -> C2402B: PIN 24 - RF14 (SENSOR - AUTOLAMP DAY/NIGHT (AMBIENT LIGHT-))=== This one is already connected to the existing sensor, must de-pin and re-pin to the new connector

The VREF- cables are supposed to meet within the two existing wire harnesses on two connection nodes S202 and S212 (look at the first diagram photo). Ford has really made this complicated because S202 is on the instrument panel harness and S212 is on the climate control system harness. Reaching these two points is impossible unless you tear the car apart so what I did is to just create a new connection node, right next to the CS2402A connector that plugs into the FCIM using a WAGO 221 Compact Splicing Wire Connecto. All cables are 22 gauge. You will need either a 4 or 5-port connector. I used this:
1716351015067-0u.png

This is where you need to make the splice to the VREF- cable to connect the discharge sensor returns.
1716354345909-a9.jpg

And here is a test 2-wire connection I did before diving into my car:
1716354427656-j6.jpg


Also, I highly recommend using a Wire Harness Cloth Electrical Tape to wrap your wires to prevent any accidental cuts in the future. This is the same tape that is used on all car harnesses. I bought this one from amazon: https://www.amazon.com/gp/product/B09S6KNNQP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Because this was the first time I was dealing with car connectors, pins, and harnesses I wanted to practice before doing any work in my car so I bought two used harnesses, which I used to extract all the cables, pins and connectors, just make sure you buy the harness from a premium car. Usually they have the car VIN from which the harness was taken so you can easily check the trim. If you know what you are doing you can just buy the parts directly. Here is what I bought:

1. HVAC Blower Motor Wire Harness fr3t-18b574-bc: https://www.ebay.com/itm/304546002940
2. Instrument panel/Dash Wiring Harness: https://www.ebay.com/itm/304525208012

In order to cut the wiring harness open and remove the wires I used a seam ripper knife like this one:
https://www.walmart.com/ip/Dritz-Seam-Ripper-1-Each/126578573?fulfillmentIntent=In-store&athbdg=L1200&from=/search

Now for the installation:

You need to remove all the front dash plastics, same as when you did the sync3 update in order to reach to the connectors in the back of the FCIM. The most tricky sensor location is the center discharge, it is in the left-most air vent on the center console. In order to reach it you must remove the car's instrument panel as well. There are multiple videos that show you how to do that, people remove it to replace it with the new digital dash. Important note: you don't need to disassemble your steering wheel for that! The footwell sensor location is right on top of where the driver's right foot is, under and behind the steering wheel. I chose to feed all the sensor wires behind the APIM and terminate where the sync3 FCIM connectors are.

Once everything is done, you need to go in with your ODB-reader + FORSCAN and make sure that the sensors are enabled. All of them are in the FCIM:

For the air discharge sensors you must go to the FCIM module configuration "AS BUILT FORMAT":
7A7-01-03 *xxx xxxx xxxx Front Left-Hand Side Discharge Sensor - Panel (FLDSP) & Front Left-Hand Side Discharge Sensor - Floor (FLDSF)
0=FLDSP not present & FLDSF not present
2=FLDSP not present & FLDSF present
4=FLDSP present & FLDSF not present
6=FLDSP present & FLDSF present <- This is what you need

For the Sun load go to the FCIM module configuration list, not the "AS BUILT FORMAT". You will see a bunch of options, if you search for sunload sensor you will find it, if it is disabled, switch the value to enabled.

The last thing you should do is to use the FORSCAN oscilloscope, add the newly added sensors and see if their values are changing:
1716353187398-x9.png


I apologize for not having photos of the installation, honestly it wasn't very hard. The trickiest part was to remove the existing non-sunload sensor from the dash and de-pin the two ambient light pins that I transfered to the new connector. It took me a couple of hours to do it, but a couple of months of research to figure out what parts I need, where do they connect, and also practice de-pin and re-pin on the used harnesses.

Happy to answer any questions
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nm_mustang

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Nice write up. How did you install the center/footwell discharge sensors? Did you have to drill a hole and glue in place or is the mounting hole available just covered up with a plastic plug
 
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AUGalos

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Nice write up. How did you install the center/footwell discharge sensors? Did you have to drill a hole and glue in place or is the mounting hole available just covered up with a plastic plug
The mounting holes are both available. The one on the center discharge has a plastic plug that is easily removed, the footwell is just empty. When installing you don't need glue to keep it in place as the sensor includes flexible plastic fins that once is pushed in the hole, will hold it in place.
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