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Another Failure -- Oh Boy

temp sensor ac air conditioning hot air blows hot

Best Answer mcgyver68 , 06 June 2014 - 08:46 AM

I had exactly the same problem after a car wash at the dealer after a service where the dealer had removed the passenger side mirror. Dealer thought they damaged the temp sensor in the mirror.  They replaced the mirror and all is well. The sensor is a little nub protruding from the bottom of the mirror.

 

I just shared this info with my dealer. Minds blown. The TSB yesterday, clearly did nothing to address this issue. And Mr. Admin; and anyone considering if the price of membership is worth it... ^^^ this right here ^^^, probably saved me at least at least ten-fold the cost of membership, in aggravation alone! A hearty thank you to ALL who have replied on this thread!!

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21 replies to this topic

#1 OFFLINE   mcgyver68

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Posted 04 June 2014 - 04:58 PM

Heading out this morning at dawn, I-10 west for South Bay, 3 stops/meetings. I noticed my indicated outdoor air temperature is erratic, up and down within a range from -40F to +179F, occasionally going to a double dash ( -- ) suggesting loss of signal. I began to wonder how many different sub-systems are multiplexed with this signal and what the effect might be. If the ECM believed the OAT, would the engine shut down?!?!  I don't know. And I am headed away from home, like in WW2 when the red light came on, you were at the point of no return. I went into my climate screen and disabled the OAT display, like a total dork, as if that would do anything; still showed on the dash.

 

Three hours later, my first meeting is done and I returned to my car which was now well soaked in the brilliant sun. Turn it on, AC on, fan fast, vents up, -- "geez its HOT today". Punched the "MAX AC" button, minute later, still blowing hot air. DaFuq?! I glanced at the dash with foreboding... FML - Damned OAT showed a steady -40F. Climate Control ECM takes its cue from the OAT signal. Yeppers, at -40F, the compressor would grenade - can't let it turn.  I power cycle the car a couple of times... no difference. I called Ford.

 

Apparently my favorite Service Advisor is "no longer with the company"... terrific. Some other young lady answered the phone, well-intentioned, but unable to help. I now had to decide if I would cancel my remaining appointments and haul ass home with ice water and windows down, or if I would man-up and suffer the heat. I had a sudden brain fart. From my limited knowledge of very simple programmable logic controls, I know that out-of-range signals can cause all kinds of hell. But a dead or missing signal, will typically cause a well designed system to revert to a limp-home or emergency operation mode. So I called back to Ford and asked for the young lady from earlier. She was unavailable and I spoke to a writer named Ken. I asked Ken if he would please go ask the EV tech, where this OAT is and if I un-plug it to null the signal, will my AC work temporarily. 

 

At this point, I am 99% sure the guy will be rolling his eyes and telling me to just bring the car in, etc. But he didn't do that at all. He was taking notes and wanted to clarify a couple things. Really??!  In 2014 America, tort lawyers on every billboard, someone is willing to use their brain, realize they aren't talking to an idiot, and do the right thing for the situation. I was amazed really. Ken said he would call back shortly. Then --- He DID!! This is what I learned...

 

C-Max energi does NOT have an OAT sensor, per se. It utilizes some kind of odd-tech pressure/temp delta sensor atop the evaporator (yes - inside the car), that some how or another talks to some other sensor somewhere and manages to figure out both the inside and outside temp via one signal. Great!  The tech advises the sensor may be accessible behind the glove box, that it is a two-wire harness. And that if it were disconnected, indeed the AC would revert to a closed loop and blow cold air. WOW!!  I also learned that there is an existing TSB on this failure mode so maybe you should ask your dealer about it next time you are in for service.  

 

As Ken was talking I opened my glove box and realized I would need tools to pull it out. Then, with the deliberate hope of a petulant child, I slammed the glove box door closed fairly hard, half-hoping it might jar this thing in close proximity behind it. I can't believe it, but the sensor came off -40F, still stayed wacky all day, but above zero indicated, and my AC continued to blow cold the whole day. Which is fortunate because FWY 60 was shut down this afternoon, causing grid lock overflow across the region. I would not have attempted to come home until after dark.

 

Off to the dealer first thing in the morning. 

 

 









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#2 OFFLINE   jdbob

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Posted 04 June 2014 - 06:10 PM

C-Max energi does NOT have an OAT sensor, per se. It utilizes some kind of odd-tech pressure/temp delta sensor atop the evaporator (yes - inside the car), that some how or another talks to some other sensor somewhere and manages to figure out both the inside and outside temp via one signal. 

 

Incorrect. The Outside Air Temperature Sensor (OAT) is in the right-hand exterior mirror. The wires are routed through the battery junction box (fuse box) in the engine compartment for some reason, going through 5 different connectors believe or not, and then into the Powertrain Control Module (PCM). That information is sent via CAN busses to the HVAC computer.

 

First thing I would do is look inside the mirror.



#3 OFFLINE   fotomoto

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Posted 04 June 2014 - 06:33 PM

+1 on the mirror.   My hybrid did after pressure washing the mirror.  

 

null_zps55b1102a.jpg

 

Got a code later on, P0600 (serial communications fault).  Canceled it and drove the car for many months, thousands of miles, and numerous washes; however, it did it again about a month ago.  Again, a day after a wash but this time the HVAC went to heat and full fan just like the OP.  I rolled down the windows, kept driving and a few minutes later it settled down and began cooling again.  No code this time and has been working fine since.  I think the OAT isn't sealed well enough.  It hasn't done it in my NRG and I wash the cars exactly the same (back to back at home with the same pressure washer).


Edited by fotomoto, 04 June 2014 - 06:35 PM.

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#4 OFFLINE   mcgyver68

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Posted 04 June 2014 - 07:30 PM

+1 on the mirror.   My hybrid did after pressure washing the mirror.  

 

null_zps55b1102a.jpg

 

Got a code later on, P0600 (serial communications fault).  Canceled it and drove the car for many months, thousands of miles, and numerous washes; however, it did it again about a month ago.  Again, a day after a wash but this time the HVAC went to heat and full fan just like the OP.  I rolled down the windows, kept driving and a few minutes later it settled down and began cooling again.  No code this time and has been working fine since.  I think the OAT isn't sealed well enough.  It hasn't done it in my NRG and I wash the cars exactly the same (back to back at home with the same pressure washer).

 

Incorrect. The Outside Air Temperature Sensor (OAT) is in the right-hand exterior mirror. The wires are routed through the battery junction box (fuse box) in the engine compartment for some reason, going through 5 different connectors believe or not, and then into the Powertrain Control Module (PCM). That information is sent via CAN busses to the HVAC computer.

 

First thing I would do is look inside the mirror.

 

 

Wow!  You know, that was my very first thought, because I washed the car last night. That's why I was looking under the front bumper, thought about the side mirrors too. That's why I was also quite surprised when this other (non-existent??) system was described. Yes Foto, that is exactly what it was doing. 



#5 OFFLINE   mcgyver68

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Posted 05 June 2014 - 02:35 PM

UPDATE:  Ford just called, car is ready. They did the AC bulletin, re-calibrated the mystery sensor in the evaporator, replaced the cabin air filter and evacuated and recharged the AC. No mention of any OAT in the mirrors. I'll ask again if I get the chance.



#6 OFFLINE   fotomoto

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Posted 05 June 2014 - 05:54 PM

Did a little parts fiche sleuthing and damn if I can find an OAT sensor located in the right mirror assembly.  Nor can I find an OAT listed for the CMax, period.  Typically they are located down low on the front end somewhere.  That location gets more attention from my pressure washer so I still think it's a water related issue........   :headscratch:



#7 OFFLINE   jdbob

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Posted 05 June 2014 - 10:22 PM

Ford refers to it as Ambient Air Temperature, maybe that's the problem. Or maybe you can only buy a complete mirror assembly and not the actual sensor (which appears to be nothing more than a 50 cent thermistor).

 

climateop.gif


Edited by jdbob, 06 June 2014 - 12:21 AM.


#8 OFFLINE   Binky

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Posted 06 June 2014 - 04:53 AM

This would likely explain the failures I had everytime it rained as well.   My car's been in the shop two months now due water related failures.   Granted not the same exact failure, but when you daisy chain 5 different systems to the ECU and CANBUS, it totally makes sense.


Edited by Binky, 06 June 2014 - 04:54 AM.


#9 OFFLINE   mcgyver68

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Posted 06 June 2014 - 05:49 AM

Here is a strange bit... Dealer took a long time to complete the job because they have to find Hybrid compressor oil, and a clean manifold to install it with. I'm wondering why in the world they have to suck the oil out of the system to perform this bulletin. The TSB did not address any sort of temp sensor outside the car. But I told the technicians what I learned here about it being in the mirror; they'd never heard of it. When I got the car back the mirror was jacked all the way to one side and there were greasy finger prints, so they were definitely looking for it. I think I'm going to go look for it today too and try to find a way to protect the device from water.



#10 OFFLINE   PJFW8

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Posted 06 June 2014 - 06:07 AM

I had exactly the same problem after a car wash at the dealer after a service where the dealer had removed the passenger side mirror. Dealer thought they damaged the temp sensor in the mirror.  They replaced the mirror and all is well. The sensor is a little nub protruding from the bottom of the mirror.


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#11 OFFLINE   mcgyver68

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Posted 06 June 2014 - 08:46 AM   Best Answer

I had exactly the same problem after a car wash at the dealer after a service where the dealer had removed the passenger side mirror. Dealer thought they damaged the temp sensor in the mirror.  They replaced the mirror and all is well. The sensor is a little nub protruding from the bottom of the mirror.

 

I just shared this info with my dealer. Minds blown. The TSB yesterday, clearly did nothing to address this issue. And Mr. Admin; and anyone considering if the price of membership is worth it... ^^^ this right here ^^^, probably saved me at least at least ten-fold the cost of membership, in aggravation alone! A hearty thank you to ALL who have replied on this thread!!



#12 OFFLINE   ArizonaEnergi

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Posted 10 June 2014 - 07:12 AM

Here's a picture of the outside temperature sensor on the passenger side mirror.  Sounds like it might be a good idea to see if the inside area above this can be accessed and some sealing goop applied.

 

Attached File  Outside Temp Sensor.png   471.77KB   7 downloads


Edited by ArizonaEnergi, 10 June 2014 - 07:12 AM.


#13 OFFLINE   makarowski

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Posted 06 July 2014 - 09:14 AM

I just had my ext temperature sensor go off in the weeds for a tad.... started my car on a warm day (85F) ... and noticed that the display was reading -40!

 

after about 1 mile or so of driving, it started moving and equalized at the right temp.  My fingers are crossed it was a loose connection, but should not have happened so soon. I'll mention it at the next service/TSB...

 

Cheers

Brian



#14 OFFLINE   honemch

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Posted 06 July 2014 - 09:15 AM

I just had my ext temperature sensor go off in the weeds for a tad.... started my car on a warm day (85F) ... and noticed that the display was reading -40!

after about 1 mile or so of driving, it started moving and equalized at the right temp. My fingers are crossed it was a loose connection, but should not have happened so soon. I'll mention it at the next service/TSB...

Cheers
Brian


I'm guessing you just washed the car...?

#15 OFFLINE   drdiesel1

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Posted 06 July 2014 - 11:10 AM

-40°f is an open in the circuit.  +167°f is a circuit short to ground. These issue's are most likely the sensor itself :victory:

 

If water can enter the sensor and conduct, it will be erratic until it dries out. I just washed my 14. I'll go have a look.


Edited by drdiesel1, 06 July 2014 - 11:13 AM.


#16 OFFLINE   drdiesel1

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Posted 06 July 2014 - 11:16 AM

No problems. It's reading normal. I'll keep an eye on this and report back if flakes out :drop:

 

It would be nice if the vehicle(s) having these issue's could have the PCM, IPC and APIM modules

scanned for DTC's. If they had an actual buss communication fault, the system should set U codes.

If it's the sensors output error they wouldn't have U Code stored, as long as it didn't cause a communication fault.

 

I'm pretty sure a com fault would show a blank or hash marks on the temperature display. My money is on the sensor as the COF!


Edited by drdiesel1, 06 July 2014 - 11:24 AM.


#17 OFFLINE   rbort

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Posted 06 July 2014 - 04:46 PM

Lesson learned from this post:

 

1.  Temperature sensor is inside right door mirror

2.  It sticks out below it, see picture above.

 

Due to this, when washing the car:

 

a) Do not spray excess water on the mirror or inside it

b) When washing the mirror be gentle and careful with the bottom side where the sensor is.

 

Knowing about this is going to help me keep mine working in good order.

 

-=>Raja.



#18 OFFLINE   makarowski

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Posted 07 July 2014 - 03:38 PM

My car was washed two days earlier... so don't think it was that... unless it was some oxidation that occurred later (and caused the temporary open circuit) ...

 

has not reoccurred since. .. so keeping an eye on it...



#19 OFFLINE   mcgyver68

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Posted 04 August 2014 - 03:16 AM

My car was washed two days earlier... so don't think it was that... unless it was some oxidation that occurred later (and caused the temporary open circuit) ...

 

has not reoccurred since. .. so keeping an eye on it...

 

Here is another update -- I just got my whole mirror assembly replaced, as it is the only way to obtain a new sensor. I picked it up from the shop and started to drive... HOT air coming from the vents and -40 on the temp indicator. Into reverse, and right back up the service drive..

 

Turns out that if the sensor loses sync, or whatever, that it must go through a re-calibration mode that involves either driving it above 20mph for >90 seconds, or leaving the car parked for >6 hours. I invited the tech to demonstrate this. He did and the AC came back working well with the correct temp displayed.

 

The tech and Service Manager agreed with me that this should be something that can be done while hooked up to the service computer in the shop. Oh well, it works well again. 

 

OH! They saved the old one for me to check out. I think the water is getting in between the halves of the mirror assembly. Look down the center where the big fat torsion spring is (collapsible mirrors) and the multi-pin connector is at the bottom, all opened up to the world.

 

Another thing... the production date on this assembly was early 2014. So they ran out of the spares over run that was projected. They have a problem. 


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#20 OFFLINE   Smiling Jack

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Posted 04 August 2014 - 11:01 AM

Here is another update -- I just got my whole mirror assembly replaced, as it is the only way to obtain a new sensor. I picked it up from the shop and started to drive... HOT air coming from the vents and -40 on the temp indicator. Into reverse, and right back up the service drive..

 

Turns out that if the sensor loses sync, or whatever, that it must go through a re-calibration mode that involves either driving it above 20mph for >90 seconds, or leaving the car parked for >6 hours. I invited the tech to demonstrate this. He did and the AC came back working well with the correct temp displayed.

 

The tech and Service Manager agreed with me that this should be something that can be done while hooked up to the service computer in the shop. Oh well, it works well again. 

 

OH! They saved the old one for me to check out. I think the water is getting in between the halves of the mirror assembly. Look down the center where the big fat torsion spring is (collapsible mirrors) and the multi-pin connector is at the bottom, all opened up to the world.

 

Another thing... the production date on this assembly was early 2014. So they ran out of the spares over run that was projected. They have a problem. 

McGyver,

 

Having seen the situation, what would you recommend to the rest of us (who have not yet had a problem) as a preventive measure?











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