AC evaporator and (probe)

[Ghosterbear]

2006 quad cab 4x4 dually. AC stopped working, took to dealer I always use. They have replaced everything and after 5 visits (loss of my truck for over 21 days) AC still does not work!
Now they are telling me that there is a probe that goes into the Evaporator that is not working and needs to be replaced BUT it is no longer available. I'm in upstate NY but I know that their are hundreds of these trucks still running down South so there has to be parts to fix my AC.
Does anyone know of a good part number for the probe? Should the probe have come with the Evaporator? Is there a current part number for the Evaporator with the probe? Is there a probe? If so what is it called? These guys unfortunately do not seem to know what they are doing with my AC.
Any help would be appreciated!
Ghosterbear

 

[BigPapa]

The evaporator temperature sensor is a two-wire temperature sensing element located at the coldest point on the face of the A/C evaporator. The probe (1) for evaporator temperature sensor is attached to the evaporator coil fins. The wire lead (2) for evaporator temperature sensor is routed through an opening at the back of the HVAC housing and the connector (3) is attached to the HVAC wire harness.

I have searched for the 5140727AA Sensor and cannot find it available, either, nor an aftermarket replacement.

This is from a 2009 post by bob4x4 on DTR. Maybe he’ll jump in and comment.

Replace the evaporator temperature sensor with part number 5140727AA. Relocate the new sensor to the upper right hand corner of the evaporator. The distances are taken from the air exit side of the core, with the top denoted as positioned in vehicle. 5 5/8 inches (143mm) from the outside LEFT plate (this corresponds with the 12th fin column from the left) 2 inches (51mm) from the TOP of the plates (not the top of the tank).

 

[DavidC]

None available ?. Is there a way to bypass with jumper, fixed resistor etc.

 

[seafish]

Rather then throwing more parts at it, my helpful advice would be to take it to a reputable automotive AC repair shop with good yelp or other good reviews in your greater area in order to find out what the problem REALLY is.

 

[sag2]

If it is single zone A/C it is no longer available. It does fit 2002-2007 trucks so finding one at the wrecking yard should not be terribly difficult.

 

[Ghosterbear]

AC is a dual zone. dual zone is what came on my Laramie.
I will talk to a good AC shop if I can find one in the area.
With all of the older trucks like mine running around in Southern States some one must know how to fix the AC. I was hoping that someone that has had their AC rebuilt would come forward with what their AC shop did to fix their AC.

 

[Prairie Dog]

Does anyone have a schematic showing this probe in the circuit?
It would be interesting to know if it's just a switch, a variable resitor or a digital input to the puter.

Scott

 

[DavidC]

From what I have read it is a switch. Kind of like the ones used on RV AC's that turn the compressor off if the coil freezes. Don't take my word for it tho without knowing for sure. If it is like that and you can't find an original a RV one would probably work if you really want it.

 

[BigPapa]

Ask and you shall receive....

 

[DavidC]

Is there a test procedure in the FSM for that sensor ?

 

[BigPapa]

The evaporator temperature sensor monitors the surface temperature of A/C evaporator and supplies an input signal to the A/C-heater control. The A/C-heater control uses the evaporator temperature sensor input signal to optimize A/C system performance and to protect the A/C system from evaporator freezing. The evaporator temperature sensor will change its internal resistance in response to the temperatures it monitors and is connected to the A/C-heater control through sensor ground circuit and a 5-volt reference signal circuit. As the temperature of the A/C evaporator decreases, the internal resistance of the evaporator temperature sensor decreases.

The A/C-heater control uses the monitored voltage reading as an indication of evaporator temperature. The A/C heater control is programmed to respond to this input by requesting the powertrain control module (PCM) or the engine control module (ECM) (depending on engine application) to cycle the A/C compressor clutch as necessary to optimize A/C system performance and to protect the A/C system from evaporator freezing.

The evaporator temperature sensor is diagnosed using a scan tool.

The evaporator temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

 

[DavidC]

So it is a resistor reading that.

 

[seafish]

So it is a resistor reading that.

correct, but even more accurately a thermistor!!

A RESISTOR is an electric component that transmits current in direct proportion to the voltage across it.

A THERMISTOR is a resistor whose resistance varies rapidly and predictably with temperature and as a result can be used to measure temperature.

 

[DavidC]

Correct. Hard to believe all these years and cannot find any values of said resistance. So with the high resistance down to a certain level the compressor runs and at some low resistance the compressor stops. I am just thinking of something like a variable resistor/rheostat that could be adjusted to at least give some AC to the OP. A rheostat with the wiper and one of the other two terminals wired would give that adjustability for the compressor to at least run. Wouldn't give any freeze protection but would at least give AC while the search goes on.

 

[BigPapa]

I looked everywhere and all I could find on specs or testing was "The evaporator temperature sensor is diagnosed using a scan tool."

 

[DavidC]

So I understand it is a two wire plug outside of the AC box. If I had one I would go unplug it and put an ohmmeter across the pins to get the number of everything ok.

 

[Bob4x4]

Remember the resistance varies with temp

 

[Motorhead]

My 2007, 5.9 with single zone AC, the sensor is accessible without dismantling the AC evaporator box. I would suggest checking some of the big aftermarket AC parts suppliers such as 4 seasons.

 

[Prairie Dog]

For some reason I was thinking this probe was in the condensor which was confusing the crap out of me.
So it's a freeze sensor for the evaporator - a common item in them. Problem is, if you just stick a resisitor in there it will never know when it freezes up. Not good.
I'm for getting one from a junk yard if an aftermarket part isn't available.

BTW, found this: https://www.moparpartsoverstock.com...oX58JWXMkaj2dqMEBIgMRGAA7AblTxO8aAv8IEALw_wcB
If you put it in the basket and go to check out, there's a place to put your VIN in to verify fitment.

Scott

 

[Motorhead]

What you really need is the proper value of the thermistor, same value as yours and splice it on to the connector that yours is on. What a stupid thing for Mopar to do UNLESS as I said above, it is available in the after market segment.
IF needed, I can remove mine and give you the resistance at certain temperatures, IF yours is the one that removes without taking the AC box apart. Find the connector where the termistor plugs into the main wire loom. Disconnect the connector. Put an OHM meter across the two posts of the thermistor. Measure the resistance at ambient temperature. Start the truck and turn on the heater and see if the resistance value changes. I sure hope this dealer you have been going to that has just thrown new parts at your truck, at your expense, refund you when you find the problem!