AC evaporator and (probe)

[Christopher McKenna]

Chris Wilson what connections did you have to fix?

Let me find the photos that I took of my controller. I will show you as soon as I find them.

Regards,
CM

 

[Christopher McKenna]

I found the controller images and am almost finished with the document for rework instructions.

I will upload it as an image shortly.

CM

 

[Christopher McKenna]

REWORK INSTRUCTIONS REV- UPLOADED. THIS IS A COMMON DEFECT INVOLVING MISSING SOLDER AT P1 CONNECTOR AT THE CONTROLLER INTERFACE OF PCBA / CCA.

Regards,
CM

 

[Christopher McKenna]

KESTER SOLDER CAN BE EASILY SOURCED AT AMAZON Amazon product ASIN B004X4L6D4
DIGI-KEY, MOUSER, ALLIED ELECTRONICS ARE WHERE I SOURCE ALL ELECTRONICS RELATED TOOLS, SUPPLIES ECT. BUT, IT CAN BE PURCHASED READILY IN STOCK FROM AMAZON QUICKER IN SOME CASES.

 

[Christopher McKenna]

Happy Saturday Morning. Hope everyone is alive and well today.

In digging into the various configurations for the RAM HVAC systems - I can definitely attest that there's conflicting information - not in this thread but, if one were to solely go by aftermarket databases - it's way off Part Number wise in many cases.

So, when investigating which PN Thermistor Assembly was used for 2006 models, OEM Mopar PN 68004239AA shows under some whacky nomenclature for starters. First, some were calling it a heat sensor while other sites listed it under AC Probe.

The other confusing aspect that throws people is the "FITS" category. Some sites list a range of fitment from 2006-2019 while other sites had listed a range of 2011-2020.

These sites - this is what leads to mass confusion and rightly so. The people inputting the data don't really know and didn't know, so, they just filled in those fields with something arbitrary.

But, I've seen these mass-flow air types in certain 2006 models myself and, we've got a fellow on here running one in a 2007 model thus, we know it went back long before 2011 when that configuration change was cut in.

And one sure way to tell is by the HAA or HAD (D=Dual Zone) that one has installed in the vehicle. If you have an easy access mount style air-flow style thermistor assembly, it will have its mount point affixed directly to the HAA or HAD injection molded clamshell. That's how one can easily identify which configuration is which.

If one has the older configuration style, sporting a direct contact probe thermistor assembly, there is no mount on the clamshell. The HAA or HAD must be removed from vehicle, clamshell case opened up 100%, access EVAP CORE, and one would find a direct contact thermistor probe assembly mounted inside the fins of the EVAP CORE.

As mentioned prior, there were two EVAP CORES and a number of PNs and revision changes to both, controller and thermistor probe assemblies thus, making it far more complicated if one didn't have the history on their vehicle such as what happened in my case involving a small family business that was in business flipping trucks. They used whatever parts they had on hand - not giving a care in the world about compatibility.

So, if one were to stuff the wrong EVAP CORE in compounded with say, the wrong thermistor and wrong controller - all bets were off of anything functioning properly.

Thus, the place to start is ask the Number One Question: What are we working with? That's when one opens everything up and starts noting all PNs for the system and, anything that cannot be identified, shall be replaced as standard default. In my case, someone had swapped the case of one controller (injection molded case) with guts from another controller thus, the PN on the outside didn't match what was on the inside. This is worst-case scenario of course. The CCAs were aftermarket knock-offs - no OEM logo, zero identification, zero Rev ID, Zero Lot Code and so forth.. it was just a bogus cob-job.

The second controller sporting OEM PN had zero solder at P1. That's the controller shown in the detailed rework instructions that came out of my personal rig that I've gutted and am overhauling. The 3rd - was purchased via a dealership. This way, I know what I'm dealing with configuration wise. No more used anything. Too risky with electronics control modules etc.

So, the first place to start is to know and understand the system and its configuration. Once established, inspect the control module. Chances are, it is defective right off the line. It's quite common. So, that's the first line of rooting and troubleshooting - inspection of the electronic control module should be done first to rule out defects at controller level. This is the brains of the HVAC system.

Following that, ALL the interconnects at the wire-harness level should be wrung-out 100% by removing the harness from the vehicle and bench testing it - wiggle and flex test and bend test while wringing it out. If at any time she drops out at the meter, you know know which conductor is intermittent and / or sporting high-impedance or worse, an open circuit / no continuity. So, run those continuity checks to determine the condition and state of the harness interconnects.

Rule and factor as much out as possible to avoid chasing and going around in circles. Once ruled out and established, then we move on to testing components such as the thermistor harness and thermistor itself. If the thermistor works to OEM SPEC or, within close proximity to spec, that component can be ruled / factored out and set aside.

Walk the path one-by-one in sequence in the cockpit side. Of course, a good quality OBD tool does come in handy as well so, if one has that type of tool, use it as your eyes and ears as well.

CM

 

[Christopher McKenna]

Monday - 6/28 UPDATE STATUS

I'll be delving into this after taking some time off of other projects to get back to this and start mapping out test plans for components that I had pulled the last go around for the raw components selected. Some of those components are still on backorder so, we'll have to go with whatever suppliers have in stock for these initial tests. Due to the short-supply side economy, it's tougher getting things in without dealing with long lead times.

Regards,
CM

 

[Bobbycat]

I'm planning on testing some of the components in the HVAC system on my truck today (hopefully). Finally got it in the shop and have a bunch of other stuff to do to it along with the freezing issue.

 

[Bobbycat]

So my 2003 with dual zone controls is tore down to the box at this point; but I haven't tested anything yet. The reason is that I ordered MOPAR 68234947AA (evap core) and a new heater core. The Evap core shows that it includes the probe in the pictures (one dealer stated that it included it as well), so we will see if it does. The odd thing is that all of the online catalogs say that it will NOT fit my 2003, but the dealerships say it's the correct part and the aftermarket parts list it as an interchange for my truck. So for the risk of it not being correct and having to pay return shipping I figured it was worth the money. I paid around $280 including shipping, and the heater core was about $90. The logic was that for under $400 I will never have to take the dash back out ever again (I'm probably not that lucky). I'm going to test the harness while I have everything apart, but I doubt that is what is causing my issue. My money is on the probe or the HVAC control head and the head can be easily dealt with after the fact. My plan is install the old probe in the new evap core next to the new probe, just in case there is some kind of a compatibility problem with the new probe.

 

[Christopher McKenna]

Unless someone updated the BOM, it will not come with the probe installed as indicated via images for, that particular component went obsolete years ago without an ALT PN thus, there's no BOM thus, there's no PN to pick and place. It used to be delivered that way - similar to how the high-side pressure line is delivered with pressure switch installed - often times, with the incorrect PN as well for certain models to varying PNs of switches included under the same, Top Level Parent PN. I also remember others ordering the EVAP / PROBE combo and it didn't come with the probe.

The dealer is (IMO) the best option for the EVAP core - also, I've got a comprehensive list of PNs for a myriad of A/C Condenser Cores right down to the OEM Supplier of the Highest Quality Evap Cores - Magneti-Marelli. These were the premium condensers that I had rooted down to manufacture of who was supplying what on the OEM Build Sheet Configuration Matrix that I've assembled for my 2005 model rig.

There were two thickness cores if memory serves me correctly after a design change was phased in that incorporated both, an EVAP and PROBE TYPE revision change. When this was rolled in exactly, is unknown but, appears to have rolled in some time in 2006. We would need VIN codes to configurations to determine how far into 2006 it went before phasing in the new core and air-flow probe assy.

Many of the condensers sold were complete and utter rubbish not to mention, the mounting points were always cheap and way off. The core thickness and densities were all over the map. I cannot tell you the number of cores I had received and inspected and wound up sending back due to being complete rubbish.

The A/C Compressor - same thing there. There should only be one compressor installed in these systems and that's the original, OEM Supplier Sanden. Brand-new, filled with proper oil - after months of investigative work, Sanden TX - hands down, makes the highest quality compressors right out of the box. Avoid remans over in Asia plants - get them drop-shipped directly out of their Texas facility / plant. This will avoid a lot of headaches down the road. It's also got the correct electronics to mate up with the wire-harness for the A/C clutch circuit to function properly already installed.

Back to the Probe ASSY. I've listed out some quick testing for these probe-assemblies in this thread that you can use to verify <FUNCTION> of the probe before installing. If you need any assistance - please don't hesitate to inquire.

Regards,
CM

 

[Bobbycat]

Thanks for the insight Chris. I ordered the OEM EVAP core and heater core (from a well known "rock" of an online retailer) for less than half what the local dealer wanted. For something like this I wouldn't use aftermarket parts unless it was a last resort. I have noted the test procedure you outlined in this thread and I plan on testing both probes (if the new one comes with it). If it doesn't come with the probe and mine tests bad, there is a Ram 1500 (I think it's a 2002 or 2003) in a local private junk yard that I have already scavenged some parts off of that still has the heater box in it as a contingency. I will report back regardless of the outcome; I think it's a dick move when someone offers help and the help-ee never even takes the time to say thank you or anything.
As a side note, as I believe Chris stated before, mine truck has dual zone temp control and everything appears to still be functional with no broken parts found yet (I am waiting to split the box until the parts for it get here).

 

[Bobbycat]

Received the Mopar evap and heater cores today. To confirm what Chris stated previously, OEM EVAP core does not come with a probe; and to make it even better, it's made in F****** China. Now trying to decide if my old USA made OEM components are better to leave in or replace with these Chinese "OEM" parts.

 

[Bobbycat]

Chris,
I have been thinking about the function of the evap probe, and had a quick question about it.
The fact that my AC works but ices up, and correct me if I'm wrong, would indicate that the probe functions, correct? The possible points of failure for icing up would be:
1. The probe is installed in the incorrect position
2. The probe has lost/drifted over time outside of calibration
3. Wiring between the probe and control head, altering signal to control giving false value
4. Control head itself
Monday I'm going to go scavenge the probe out of the local parts truck; and test both under the same conditions per the test procedure you outlined earlier and see how close they compare to each other at the same temperatures.

 

[Christopher McKenna]

Bobbycat,

Sorry for not getting back to you sooner.
Torn rotator cuff on me end has made everything difficult.
Let's walk the path and root things out by ruling out as we go.

VERIFY PROBE COORDINATES
Ensure x and y placement matches what's shown on the super-imposed photo for thermistor probe location on the EVAP CORE on this thread. I drew out a crude x, y coordinate over EVAP CORE for correct placement of thermistor assembly.

ELEC TEST AMB: VERIFY THERMISTOR OHMS AT AMB TEMP
NOTES AND WARNINGS SECTION: DO NOT APPLY VOLTAGE OR CURRENT TO COMPONENT. DO NOT APPLY THERMAL HEAT VIA FLAME ---> CATASTROPHIC FAILURE AND OR DAMAGE <---WILL OCCUR TO COMPONENT. DO NOT DROP, WHACK, OR OTHERWISE SUBJECT PROBE TO IMPACT SHOCK.

1. GENTLY (DO NOT DROP / IMPACT SHOCK PROBE) REMOVE THERMISTOR PROBE ASSY FROM VEHICLE.

2. SET DMM TO OHM AUTO: VERIFY OHMS AT AMB TEMP ~77F. DMM OHM READING _____________

3. VERIFY R25 VALUE IS ~5000 OHMS @ AMB / ~77F ROOM TEMP. PASS ______________ FAIL_______________

4. <IF> STEP 3 = PASS PROCEED TO STEP 5: ELEC TEST COLD. <IF> OHM READING FAILS TO MEET AMP SPEC = FAIL. [ABORT TEST]. CHECK LEADS OF THERMISTOR ASSY TO ENSURE THEY'RE NOT BROKEN INSIDE SLEEVING. IF THERMISTOR PROBE LEADS CHECK OUT 100% - THERMISTOR UNIT DEEMED DEFECTIVE / FAULTY / HARD FAILURE. REPLACEMENT REQUIRED.

5. ELEC TEST COLD: VERIFY THERMISTOR OHMS AT COLD TEMP
ATTACH DMM PROBES (clip-on FLuke_micro leads or, rude but works: form tight loops on thin wire paperclips and slip over pin contacts) TO CONNECTOR LEADS OF THERMISTOR

6. PLACE PROBE ASSY IN PLASTIC ZIP LOCK BAG. CLOSE BAG. SECURE DMM LEADS WITH TAPE TO BAG. PLACE BAG INTO ICE MAKER INSIDE FREEZER. NOTE: CAREFULLY RUN PROBE LEADS OUT THE DOOR SEAL WITHOUT YANKING / TUGGING ETC.

7. DWELL DUT (DEVICE UNDER TEST) UNTIL OHM READING BOTTOMS OUT / STOPS MOVING ON DMM. NOTE OHM READING OVER DURATION OF DWELL TIME / SOAK TIME. MONITOR DMM READING DURING THE ENTIRE TEST WHILE WATCHING FOR ERRATIC READINGS THAT MAY JUMP OR DROP OUT. THIS WOULD READ INFINITE / OPEN CKT.

8. NOTE OHM READING WHEN PROBE TEMP REACHES EQUILIBRIUM. DMM DISPLAY WILL DISPLAY A CONSTANT VALUE. THIS IS WHAT IS TO BE RECORDED ALONG WITH TEMP AND HOW LONG IT TOOK TO REACH EQUILIBRIUM.

DWELL TIME _____________ MINS

OHM READING AT EQUILIBRIUM _____________

TEMP AT EQUILIBRIUM _________________

<END>

Report back whenever possible. I'll compare plots that I've done in the past and see what we're working with here on the Thermistory Assy before moving onto the other control system items.

Regards,
CM

 

[Bobbycat]

I removed the dash and box out of the junkyard truck and got the thermistor. The junkyard truck was a 2002 per the VIN plate, my truck is a 2003 (Feb if I remember correctly). From here on out I will refer to the sensors as 02 and 03. I tested two sensors at the same time with the same meter, to get reading as comparable as possible, temperatures were taken with a non contact IR temp gauge set at .95 emissivity.
02 Temp. 03
4.55K. 82F. 4.54K
6.00k. 72F. 5.97K
6.15K. 70F. 6.13K
30.50K 5F. 33.45K after about 55 mins.

The two sensors are different in appearance also, and I can take a picture of them if that is helpful. Given what I have seen so far, it looks like the 03 sensor is actually the better out of the two, despite my freezing issues. It's also worth noting, both sensors were installed in the incorrect location. I really wish I could find a new sensor to confirm what the values should be.

 

[Christopher McKenna]

Bobbycat,

Let's get the images of both sensors into this thread for documentation purposes. I've been compiling a configuration matrix and would like to upload the images. I always wondererd how far back this 3rd gen HVAC sensor design went to the point engineering rolled out the 2005.5 - unknown 2006 configuration change. This is what most interests me is the control systems configurations.

I'll pull my log files from my library and start review of the sensor outputs.

Thanks,
CM

 

[Christopher McKenna]

BC:

Upon looking at the data there, it's immediately recognizable on my end at least, that we've got the same type of component sporting the same R25 value.

The AMB TEMP OHM reading indicates both components inside the probe are 5K.
Both probes are NTC Types (as are most in HVAC systems).
R25 value @ 82F is NORMAL / PASS. For, at 77 degrees, it will read 5K +/- tolerance limits.
As temperature declines: @ 72 degrees, resistance increases which is how NTCs function by design.
A reading of 6K and 5.97K is negligable. The delta there is the difference in resistance in cabling if using two different sets of leads. If using same set of test leads, factor that out and we're looking at tolerance deltas.
@ 70F - 6.15 VS. 6.13 K-Ohms is negligable. Delta tolerance or cabling delta. However, it doesn't matter for, the numbers are merely reflective of the same thing.

You've got two sensors that function indentlcally with a slight variance at extreme low which again, is negligable. Since we don't have the whole curve (and that's fine), we cannot determine where the two start to drift but, again, negligable in this case.

These sensors are perfectly fine.

CM

 

[Christopher McKenna]

I'll bet, once the sensor is located in the correct flow lane, the controller (if working properly), will finally see proper input thus, it will finally be able to control the compressor.

What had occurred back then, was an inversion, which wound up as a misprint in the OEM manual with regards to installation location of the thermistor. I know that for a fact so, that's not a mystery. Since I don't own any air-flow test equipment, I cannot test for dead-zones properly.

But, knowing how stuff works, I assume there was either a dead-zone or, warm air was constantly blowing over the probe in that location (hot spot) thus, the output reading at controller input never hit the upper limit thus the compressor remained engaged 100% thus, freeze-ups would occur.

They either had a flow problem due to design differences involving the HAD systems. The HAD systems appear to be more problematic based on user feedback.

You may find that, once the probe is mounted in the correct orientation at the EVAP CORE, the controller will disengage compresssor from circuit as designed but, we still need to verify the other items. Those are open items that need to be checked off the list.

CM

 

[Bobbycat]

Chris,
Thank you for the help and knowledge that you have brought to this discussion.
Where the sensor was located appears to be almost as far away from the incoming refrigerant as possible, so I can see that being the cause of my problems. I will try to test harnesses tonight, but I'm a little reluctant to take the controller apart (I don't want to damage it if it's good) until I get everything back together and function test the AC with juice in the system. I also figured that the controller is extremely easy to get to compared to everything else. I'm waiting on the defrost door (it was mostly stripped out on the coupler, but still seemed to work). The door in the 2002 was completely broken and usable. Dorman makes some aftermarket (aluminum critical components) replacement doors for these trucks; the defrost door is on order.
I got to wondering about compatibility of HVAC parts in newer truck, like a 2007-8 and using the controller, sensor and box? The body style is the same so it could be an option of ducting and wiring was compatible.
When I start getting deep into things like this it really makes me loose faith in the "Dodge" parts of the truck. I can honestly say, if they didn't have a Cummins engine in them I would never own one.

 

[Bobbycat]

I'll bet, once the sensor is located in the correct flow lane, the controller (if working properly), will finally see proper input thus, it will finally be able to control the compressor.

What had occurred back then, was an inversion, which wound up as a misprint in the OEM manual with regards to installation location of the thermistor. I know that for a fact so, that's not a mystery. Since I don't own any air-flow test equipment, I cannot test for dead-zones properly.

But, knowing how stuff works, I assume there was either a dead-zone or, warm air was constantly blowing over the probe in that location (hot spot) thus, the output reading at controller input never hit the upper limit thus the compressor remained engaged 100% thus, freeze-ups would occur.

They either had a flow problem due to design differences involving the HAD systems. The HAD systems appear to be more problematic based on user feedback.

You may find that, once the probe is mounted in the correct orientation at the EVAP CORE, the controller will disengage compresssor from circuit as designed but, we still need to verify the other items. Those are open items that need to be checked off the list.

CM

Chris, do you think it is worth while to install the spare sensor as a backup in the box, or do you feel that is a wasted redundancy?

 

[Christopher McKenna]

Hello again BC.

Do not run two thermistor assemblies concurrently. It's the equivalent of running two resistors or caps in parallel thus, the circuit will MALFUNCTION. I am 100% confident failure will occur.

The driver circuit is designed around a 5V reference signal. It cannot handle doubling current draw.
The input sense circuit and divider is designed around a single input channel signal only. Long story made very short - the answer is no regarding redundancy. Should one want to place a backup sensor in case the primary sensor goes out, this could easily be done.

At some point while re-assembling my own HVAC system to better than OEM condition, I will be looking into designing two access panels - one for the thermistor assembly and secondly, one for an incoming air-filter that slides in and out of the HAA complete with proper gaskets and / or seals.

In general, redundancy in electronic control systems, in space satellite systems for example, redundancy involves two or more of everything running on their own separate BUS lines to basically, in short, it's a complete system redundancy that is isolated from one another.

I will instruct you how to remove and open the control module. The CCA integrity and workmanship must be verified. Removal of controller from vehicle is as simple as removal of a panel and four screws. That's it. The rest is plastic tab retention securing the cover and rear housing together. One simply must carefully pry two halves apart. I use plastic spudger tools whenever working with plastics - like door panels and mobile devices.

These controllers are quite easy to open and inspect without incurring any damage. I can instruct - complete with photos on the "How To" aspect but, this is a must for, we need to at the very least, inspect the solder to pin interface of the control inputs.

I will take the time to put forth the documentation if needed without question.

Next up is mention of mixing year, make and model - in particular, swapping for example, a 2007-2008 HVAC system into a 3rd Gen. Mechanically, if the envelope allows it and the mount points are the same - and, even if they don't, anyone with mechanical fab skills can make the HAA fit.

However, a number of constraints may occur such as interference between the dash frame and the HAD envelope. The other area is how the plumbing aligns and comes off the distribution center into the dash - it may or may not work.

But, the biggest hurdle that isn't as easy to resolve like mechanical form & fit is the function aspect and that functionality is rooted in the electronics. In particular, the entire electronics systems - not just the HVAC controller. The entire system - right down to the relays used inside the Power Distribution Center (PDC) to newer style fuse boxes as in my 3rd Gen which is not a TIPM but, rather an IPM (Integrated Power Module) is not the same design as the TIPMs found in the later model Rams. This leads us to a major mis-wire condition for, the wire-harnesses for IPM are not the same as a TIPM (Totally Integrated Power Module) thus, a later control module will not be able to communicate with the ECM.

That one change to a latter configuration at the HVAC level would drive change throughout the entire Ram electrical - right down to the seatbelt modules and even, possibly, stuff as simple as the fuel pump sending level.

I know the HVAC controller is tethered to and communicates with the ECM module. The ECM module is tied to the relays inside the IPM module not to mention the clutch fan circuit - the list is beyond extensive as to the number of engineering changes imparted just from changing out the HVAC controller. It's way too risky. I've thought of doing this myself in the past year during tear down of the cab. It's a no-go. Could it be done? Oh yes. Totally but, not without changing the entire vehicle over electronics wise via ripple effect.

Regards,
CM