AC evaporator and (probe)

[DavidC]

As far as I know there was no freeze control thru 2002. What makes it so special now ?. Is it the dual zones ?. You would know if it froze as air flow would be diminished, it happens in the RV once in a while depending on weather and running thru the ductwork but I can turn the compressor off and let the fan run to defrost. When running thru the quick cool straight out of the AC it never freezes. I agree the correct thermistor is the ticket as you could at least replace it and hopefully the manufacturer does not stop making it. Usually freezing comes from bad airflow/design so again why do these trucks even have this.

 

[Prairie Dog]

In post #19 I listed a link to what looks like the correct OEM part. It's only $41 and for that, I wouldn't reinvent the wheel.

 

[Ghosterbear]

Thanks for all the help and suggestions. There are no sensors available through dealers or from aftermarket outfits that I can find. Biggest local junk yard that usually has everything is telling me no. Someone must have figured out a way to solve this problem as there are 100s of these trucks still running in the south and up here.
I am going to take truck up to Rochester area AC place that has a good rep to see if they can fix it.
In the back of my mind I have the feeling that the dealers tech threw the sensor out with the leaking evaporator because he didn't know what it was for or thought he would get a new one with the new evaporator. I hope I am wrong about that but dealer is saying that the sensor is the problem but the couldn't tell me how they finally figured that out.
Ghosterbear

 

[Motorhead]

Thanks for all the help and suggestions. There are no sensors available through dealers or from aftermarket outfits that I can find. Biggest local junk yard that usually has everything is telling me no. Someone must have figured out a way to solve this problem as there are 100s of these trucks still running in the south and up here.
I am going to take truck up to Rochester area AC place that has a good rep to see if they can fix it.
In the back of my mind I have the feeling that the dealers tech threw the sensor out with the leaking evaporator because he didn't know what it was for or thought he would get a new one with the new evaporator. I hope I am wrong about that but dealer is saying that the sensor is the problem but the couldn't tell me how they finally figured that out.
Ghosterbear

Going to a SPECIALIST, especially in the Hot and Humid area that you live in is probably your best bet. I would seriously consider that if they fix your system, (I sincerely hope they do), I would ask them for a print out on what the REAL cause was. If it was something that your dealer didn't do with all the expensive parts they threw at your truck, I would take that writeup and the invoice form the A/C shop to the dealer and DEMAND a refund.
Quick story: A friend of mine referred a lady to me that had a late 90's Jaguar sedan. This was after FORD bought out Jaguar. The car had a 4.0 ltr naturally aspirated V8 that kept eating up and throwing the serpentine belt. She had even taken the car to a BIG Jaguar dealer in Santa Barbara, spent $1200 and the serpentine belt failed again at about 2,000 miles like it had before. Jaguar had TWO Ford built V8's for that car, both 4 litre, one Naturally Aspirated and one Supercharged. I looked at the belt while the car was running and noticed that the belt as it rode over the water pump serpentine pulley, it rode up on both sides of the belt. I RESEARCHED and found out that the SUPERCHARGED engine used a 5 groove serpentine pulley setup and the N.A. Engine used a 6 groove pulley system. This car had either from the factory or someone had put the supercharged pulley with one less grove on the water pump. As I recall, this car only had about 30,000 miles but was out of warranty. I ordered the right pulley from the same Jaguar dealer in Santa barbara and fixed the car. I'm Mr "Nobody" other than I have worked out of my home on cars and equipment for over 40 years.
Anyhow, The dealers mechanics never took the time to "LOOK" at and for the problem. They just threw new parts at is and moved on.
I did a write up for her and gave her the old pulley which she took to the Jag dealer and was given a FULL refund of $1200 and had a car that she could now trust. This AC shop you are going to will more than likely fix your truck PROPERLY. My fingers are crossed for you! Let us know what the outcome is. Chris

 

[BigPapa]

There are no sensors available through dealers or from aftermarket outfits that I can find.

I checked out the link that Prairie Dog posted:

https://www.moparpartsoverstock.com...oX58JWXMkaj2dqMEBIgMRGAA7AblTxO8aAv8IEALw_wcB

I went all the way to putting in a payment and it said nothing about them not having it. If I was you I'd try to order it from them, call them if you can. I didn't check to see if they had a number posted.

 

[sag2]

The factory scan tool reads the evap temp. No testing is required.

 

[Ghosterbear]

Went to local Dodge dealer as they have a great parts guy. Plugged in my Vin# and it brought up a totally different temperature sensor number!
He dug into it further and since my 2006 was manufactured on 11/30/2005 it has a different P/N and sensor in it. 3500 Cummins manufactured after 5/30/2006 have the sensor number that everyone is using. Hope parts guy is right as the new sensor number is in stock. I will double check him at one of the other local parts guys using my Vin. number. Whatever I find out next week I will let everyone know.

 

[Doc Holiday]

Went to local Dodge dealer as they have a great parts guy. Plugged in my Vin# and it brought up a totally different temperature sensor number!
He dug into it further and since my 2006 was manufactured on 11/30/2005 it has a different P/N and sensor in it. 3500 Cummins manufactured after 5/30/2006 have the sensor number that everyone is using. Hope parts guy is right as the new sensor number is in stock. I will double check him at one of the other local parts guys using my Vin. number. Whatever I find out next week I will let everyone know.

So what’s the correct part number?

 

[Ghosterbear]

My P/N for the temperature sensor probe is:#68004239AA I know it is good because I ordered one and have received it.
The P/N for the evaporator core with o-rings is:#68138270AA or AB I am not sure on this as one parts guy says it ends in AA and that evaporator is on BO till August. The other parts dealer says it is available as AB and it will be at the dealer tomorrow AM. The dealer that printed out the AC parts list and schematic shows AB. Will update as I find out.

 

[Ghosterbear]

OK for 2006 3500 Cummins 4x4 Quad Cab dually trucks built before 3/17/06 (LIKE MINE)
`Evaporator Kit AC P/N 68004242AA $318.25 at my local Dealer at other dealers $424.00 5 to 10 day delivery or 2 to 3 days for $28. UPS ( It is not stocked in our local delivery area Cleveland, Ohio so it has to be shipped from somewhere else?)

AC temperature Sensor Probe P/N 68004239AA $30. (This is the same probe used in the later models per my parts guy)

Now if I can only get my AC fixed by the dealer that has worked on it 6 different times and told me if I could find the Temperature probe that He would install it for free. This would require them to pull out my dash again, a 5 hour job per their "book".
If anyone is interested I will let them know how I make out.
Ghosterbear

 

[sag2]

The guys that have done a few take about 45 minutes to get it apart.

 

[Christopher McKenna]

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.

While overhauling the entire A/C system on my rig, I took the time to verify the range of the thermistor and sure enough, this particular design sports a wide range - 40-degree C span. It may go much further under colder temps- that was AMB to 32-degrees.

Since many manufacturers define the characteristics of the NTC to align with the feedback circuit at the controller level, one has to carefully choose the correct replacement. Varying brands say from a KIA for example, will measure 2k Ohms at Ambient and only hit 8k Ohms at ice up. This is why it's important to match the curve and response to controller.

Electronics supply houses such as Mouser, Digi-Key, Allied and so forth, would be a start for a replacement for this component that went EOL (End of Life).

I've not found a source that's OTS (Off-The-Shelf) for this particular thermistor myself yet.

 

[Christopher McKenna]

The other aspect for anyone seeking information on HVAC is with regards to placement of the NTC probe on the evaporator. The information presented herein is actually old and out of date. The photo's shown are from the service manual which contains gross errors - incorrect sensor location for 2004-2005. 2006, I'm not certain but, when having issues sourcing parts, I had to use 2004-2006 BOMs along with emailing Chrysler about the confusion and errors with parts and supplier listings for HVAC components - in particular, 2005 2500 Cummins model.

The photo shown from the service manual represents the 2003 model - 2004.5 evaporator temperature sensor probe location. That location, is actually in the bottom half of the HAA / HAD molded part and is incorrect. The evaporator core mounts into the top half first to align its plumbing to mold. The plumbing side is actually the top of the HVAC HAA / HAD (Dual) when mated to the other half of the HAA mold and assembled into the vehicle.

I've got this system down pat from 2004-2005 due to encountering plethora of documentation and parts and materials issues when rebuilding it into a new-condition system but, with far better materials (foam seals) that will outlast the OEM design.

What happened was, due to placement of that sensor in the drip pan, the core would freeze up. I believe this to be gross error. Reason I say this is, it's actually inverted in location thus, either the tech writer writing the manual made an error and they never bothered to update the manual and roll the rev and / or, there was a gross error in engineering where they flipped it.

In year 2004.5 - an engineering memo, not a TSB sadly, went out to relocate the sensor. Some engineering group (STAR) was the one who disclosed the change I believe to shop techs at dealerships. Many have had to phone engineering in order to obtain information on this system - dealers included.

Reportedly, 2005 was the first year the change was implemented off the line thus, if one had a 2005 model, the sensor was already located in the correct location. Sensor location: 2.125 in. on the z-axis (measured from edge of cooling fins near plumbing) and 3.750 in. on the x-axis / 8 rows in. Sensor probe is then inserted into the 8th row with its barbed anchor tang into row 7, mounted on its left-face (driver-side) as mounted in vehicle. This would be the exit side of the air flow.

Sensor length is 1.125 in. Core thickness is 2.750 on newer cores and 2.875 on the older core. This is for a 2005 model. Older core was heavier and densely packed vs. open and see-through on the new OEM Mopar Evap Core.

In order to find the correct replacement A/C evaporator temperature sensor that will work with certain year models, we would need to know a few things about the design. In particular, what the reference signal is. It could be a 5V reference signal but, to be certain, we'd have to find the two contacts at the harness level that mates to the dashboard harness and take a reading to see what voltage is being fed to this sensor. This is one parameter when selecting a probe like this. The second would be what is its max operating temperature and it's min operating temp along with the base type and lead type and lastly, it's Ohm specification. This is measured at 25C and is another spec to fill in when ordering a probe.

I will email Chrysler Dodge and ask engineering what this sensor is and see if they respond. They've responded to my inquires in the past in a matter of hours. If they don't respond, that means some reverse engineering would be required in order to source replacements for the plug in probe PN 5140727AA.

Hopefully we can get some answers and more importantly, HVAC components that went obsolete.

CM

 

[cwbyinjeep]

The other aspect for anyone seeking information on HVAC is with regards to placement of the NTC probe on the evaporator. The information presented herein is actually old and out of date. The photo's shown are from the service manual which contains gross errors - incorrect sensor location for 2004-2005. 2006, I'm not certain but, when having issues sourcing parts, I had to use 2004-2006 BOMs along with emailing Chrysler about the confusion and errors with parts and supplier listings for HVAC components - in particular, 2005 2500 Cummins model.

The photo shown from the service manual represents the 2003 model - 2004.5 evaporator temperature sensor probe location. That location, is actually in the bottom half of the HAA / HAD molded part and is incorrect. The evaporator core mounts into the top half first to align its plumbing to mold. The plumbing side is actually the top of the HVAC HAA / HAD (Dual) when mated to the other half of the HAA mold and assembled into the vehicle.

I've got this system down pat from 2004-2005 due to encountering plethora of documentation and parts and materials issues when rebuilding it into a new-condition system but, with far better materials (foam seals) that will outlast the OEM design.

What happened was, due to placement of that sensor in the drip pan, the core would freeze up. I believe this to be gross error. Reason I say this is, it's actually inverted in location thus, either the tech writer writing the manual made an error and they never bothered to update the manual and roll the rev and / or, there was a gross error in engineering where they flipped it.

In year 2004.5 - an engineering memo, not a TSB sadly, went out to relocate the sensor. Some engineering group (STAR) was the one who disclosed the change I believe to shop techs at dealerships. Many have had to phone engineering in order to obtain information on this system - dealers included.

Reportedly, 2005 was the first year the change was implemented off the line thus, if one had a 2005 model, the sensor was already located in the correct location. Sensor location: 2.125 in. on the z-axis (measured from edge of cooling fins near plumbing) and 3.750 in. on the x-axis / 8 rows in. Sensor probe is then inserted into the 8th row with its barbed anchor tang into row 7, mounted on its left-face (driver-side) as mounted in vehicle. This would be the exit side of the air flow.

Sensor length is 1.125 in. Core thickness is 2.750 on newer cores and 2.875 on the older core. This is for a 2005 model. Older core was heavier and densely packed vs. open and see-through on the new OEM Mopar Evap Core.

In order to find the correct replacement A/C evaporator temperature sensor that will work with certain year models, we would need to know a few things about the design. In particular, what the reference signal is. It could be a 5V reference signal but, to be certain, we'd have to find the two contacts at the harness level that mates to the dashboard harness and take a reading to see what voltage is being fed to this sensor. This is one parameter when selecting a probe like this. The second would be what is its max operating temperature and it's min operating temp along with the base type and lead type and lastly, it's Ohm specification. This is measured at 25C and is another spec to fill in when ordering a probe.

I will email Chrysler Dodge and ask engineering what this sensor is and see if they respond. They've responded to my inquires in the past in a matter of hours. If they don't respond, that means some reverse engineering would be required in order to source replacements for the plug in probe PN 5140727AA.

Hopefully we can get some answers and more importantly, HVAC components that went obsolete.

CM

I have truck apart and while we've not verified the sensor is bad, I have had freezing of the AC and needed to go to fresh air/compressor off to thaw the core several times the past couple years (truck only goes 6-10k miles a year). If I don't go to full cold setting and run blower on speed 2 or 3 it doesn't freeze up. So now I have a dash completely out of the truck at buddy's shop and he'll need to get it back together and out of his way in next day or two and stuck trying to solve this temp sender issue on a 2003 3500 Laramie/dual zone. FUN!

 

[Christopher McKenna]

Hey there. After reading your post twice:

1. Since we know the core is icing up - this is an indicator the thermistor isn't open nor shorted thus the reason why the A/C compressor still receives energy to clutch coil. However, the thermistor values could be out of tolerance and /or out of range thus, be partially functioning. It could also be due to Item 2.

2. We also know that on 2003-2004.5 that icing was due to incorrectly locating the sensor at the evaporator due to engineering or the supplier inverting the assembly. Remembering when A/C sensors used to come preinstalled on EVAP cores from the dealership and aftermarket suppliers. In fact, a lot of them still run the outdated images showing the assembly of both PNs sold under the EVAP PN.

In this case, since we know that the core is icing over - probable root cause coule be a mis-located NTC sensor.
To remedy the issue, simply relocate the sensor and retest. Take note of its location before removing.

If you have a DMM, you can test the sensor quite easily. I've got a procedure I can write out should you desire to test it outside the vehicle.

On my end, Dodge hit me back via email. I hope to have an answer shortly on either a work-around or a superseding PN that's readily available. I did start the process of sourcing a thermistor along with parts to fabricate a new harness assembly if it comes down to it that we're left out to dry with regards to the part being obsolete. I believe it was originally manufactured in Germany. Possibly by Bosch come to think of it.

CM

 

[cwbyinjeep]

Hey there. After reading your post twice:

1. Since we know the core is icing up - this is an indicator the thermistor isn't open nor shorted thus the reason why the A/C compressor still receives energy to clutch coil. However, the thermistor values could be out of tolerance and /or out of range thus, be partially functioning. It could also be due to Item 2.

2. We also know that on 2003-2004.5 that icing was due to incorrectly locating the sensor at the evaporator due to engineering or the supplier inverting the assembly. Remembering when A/C sensors used to come preinstalled on EVAP cores from the dealership and aftermarket suppliers. In fact, a lot of them still run the outdated images showing the assembly of both PNs sold under the EVAP PN.

In this case, since we know that the core is icing over - probable root cause coule be a mis-located NTC sensor.
To remedy the issue, simply relocate the sensor and retest. Take note of its location before removing.

If you have a DMM, you can test the sensor quite easily. I've got a procedure I can write out should you desire to test it outside the vehicle.

On my end, Dodge hit me back via email. I hope to have an answer shortly on either a work-around or a superseding PN that's readily available. I did start the process of sourcing a thermistor along with parts to fabricate a new harness assembly if it comes down to it that we're left out to dry with regards to the part being obsolete. I believe it was originally manufactured in Germany. Possibly by Bosch come to think of it.

CM

My truck is an 03 and to my knowledge no one has ever been in the dash,..i've owned since 2004 and 19k miles. So if they didn't address the issue by May of 2004 I already had it. One of the damper doors was stripped, but it's always been finicky, just made it work but not running it at full cold and dual zone has always worked until past year. Any help on verifying we're working with a good sensor would be awesome and I'm having a hard time locating any picture (for dummies) of the correct sensor placement. It appears to be much lower than 2" as it is now from top of body (not tank)

 

[Christopher McKenna]

Dodge didn't address it until 2005 during new builds. I believe that only under certain conditions ice buildup on the cores was forming. Many running 2003 - 2004.5 ran for long periods of time without issue. I think that's why it took until 2005 to change it. Ice was probably not forming 100% across all models. However, that still doesn't rule out a faulty sensor that is partially functioning. We can cover that test later.

I listed the dims out earlier but decided to snap a pic of my core and put some dims on it to help you out quickly. Hopefully this will help.

 

[Christopher McKenna]

Typically the temperature of the core operates ~ 10 degrees above freezing to avoid formation of ice crystals. So, when one encounters ice, there's three primary root causes involved and they are:

1. lack of airflow over coil
2. small leaks in evaporator
3. low refrigerant level

Now, with these Dodge Ram HVAC HAA systems in general - they should be gutted and overhauled and improved beyond the OEM design. While the mechanical engineering was spot on with the mold of the HAA / HAD upper and lower half along with ingenious cooling for the blower motor, there were serious flaws at the materials engineering level. In particular, the doors and seals.

The door material was brittle and over time, it would stress under torque loading thus, fatigue failures are still common. All the doors should be gutted and replaced along with all the foam seals throughout the distribution center and dash duct level. Blend door dot com sells nice aluminum doors. However, the seal material will dry rot over time thus, if one is ambitious enough, the foam should be replaced with a more reliable and long-life material. If anyone is seeking information on how to overhaul and what materials to use, please feel free to inquire. One will want to use HD actuators rated for high current / high torque applications to ensure tight seals and long life.

Since overhauling my rig towards a global expedition vehicle, I gutted the dash down to the frame and am redoing the wiring as needed thus, it was easy to gut the entire HVAC system from engine bay to cockpit in a single go. I had the time to tear-down and source materials suited for the end-use environment and application that will outlast the OEM design.

IN VEHICLE TEMP SENSOR TEST
Note: this is a gross test vs engineering level test involving thermal cycling at known temps while monitoring output curve. This would require testing outside the vehicle post removal of the HAA / HAD unit and sensor from the vehicle. This will at least show whether its outputting or not. Some hand held programmers (Snap-On) have built in test capabilities to test this sensor in vehicle but, typically, with the vehicle running etc. Some programmers feature a thermal warm up in certain thermistor applications thus, even when not running, they can heat it and allow it to cool.

PROCEDURE​

1. DISCONNECT TEMP SENSOR CONNECTOR FROM MAIN HARNESS
2. BACKPROBE CONNECTOR (NOTE: USE MINI PROBES OR PAPERCLIPS IF PROBES DON'T FIT. BE CAREFUL NOT TO CRACK CONNECTOR)
3. VERIFY RESISTANCE AT AMBIENT (AMB) - EXPECTED OUTPUT: 4K TO 7K OHMS DEPENDING ON TEMP INSIDE HAA UNIT.
4. REMOVE BLOWER MOTOR ASSY
5. SPRAY FREEZE SPRAY IN SHORT BURSTS AT CORE. WE DON'T WANT TO INDUCE THERMAL SHOCK - SHORT BURSTS SHOULD SUFFICE.
6. VERIFY RESISTANCE AT COLD - EXPECTED OUTPUT: RAPID INCREASE IN RESISTANCE. AT ~ 32F, 16K OHMS IS EXPECTED
7. OBSERVE RESISTANCE DROP AS SENSOR WARMS UP.
8. REPEAT TEST 3X WHILE WATCHING FOR ERRATIC OUTPUT VIA DMM DISPLAY.

​

 

[Bob4x4]

Interesting reading but the evap temp is very close to 32 degrees,the outlet air temp is close to 10 degrees warmer than evap

 

[Christopher McKenna]

Depending on refrigerant and psi specification, it varies in temp but, in principle, the evaporator's external surface temp is typically kept above freezing to prevent ice from forming. And remember now, there's specified internal refrigerant temp at x psi vs. surface temp. There's a differential there due to air flow and heat transfer rates etc thus why an evaps surface temperature is higher than specified internal temp for the medium. If it were freezing or below freezing, I would imagine a lot of ice-overs.

Now, in looking into the HVAC controller and its control circuit - it's definitely a 5-volt reference signal with a switched ground via controller after looking into the testing of the circuit and systems level diagrams.

For what it's worth, I once had an issue with a controller in the 2005 2500 Cummins - PN 550556321 Rev AD (single zone / HAA controller) The DOM on the old controller Rev AD was March of 2004
Upon opening it up, I found missing solder at the interface connector. Not a single pin was soldered to the board thus leading to intermittent issues. I soldered the pins in and that solved that intermittent and erratic controller issue. I've since updated the controller the latest revision (AE).

I would open the controller and inspect for missing solder. . I can show you via pictures later on what to look for if interested. The controller you'll have will be for a dual zone but, the same principle applies for the electronics inside.

So, if were to list out common modes of failure here:

- TEMP SENSOR - forks - three failure modes: 1. thermistor failure. 2. Bad Ground. 3. Bad reference signal, 4. Noise interference from other electronic devices
- CONTROLLER - forks - wonky software, poor workmanship and / or circuit design, noise, bad or intermittent ground, bad or intermittent reference signal
- A/C EVAP - gross failure (leak), restricted airflow, temp sensor placement / location - debris blocking airflow to sensor.

There's a test to verify the reference signal but you'd have to have it all together. I can provide you with that test later when the dash has been installed.

Regards,

CM