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AC Fix TSB (Pre 8/20 build trucks)

Seeing all these horror stories… I’m getting cold feet. The 2019 I just bought hasn’t had the TSB done (whether that’s a good thing or bad thing idk).

I’m thinking of just doing this job myself. Parts cost is about $200 for everything shipped to my door. Maybe add a few bucks for a tech authority subscription for directions…

Doing it myself ensures there are no cuts/tears and no antifreeze spilled as I cap heater cores before I remove HVAC boxes.

Anyone think I should do it and post a step by step?
 
cumminsturbofreak said:
Seeing all these horror stories… I’m getting cold feet. The 2019 I just bought hasn’t had the TSB done (whether that’s a good thing or bad thing idk).

I’m thinking of just doing this job myself. Parts cost is about $200 for everything shipped to my door. Maybe add a few bucks for a tech authority subscription for directions…

Doing it myself ensures there are no cuts/tears and no antifreeze spilled as I cap heater cores before I remove HVAC boxes.

Anyone think I should do it and post a step by step?
Click to expand...
Usually your DIYs or mod threads that i have seen on the other form are great so for sure!
 
So iv been following this issue for poor AC for 2 summers now. I have a 2019 3500 Limited. My AC is pretty pathetic. I have been to the deler 4 times now. Last week they did the so called TSB for housing and eveap replacement. The AC is only blowing 50 degrees...... I am experienced with AC as a tradesman.... I have 2 Toyotas that both blow at 39 Farenheight, they blow so cold i have to turn the blower down.
Now back to the Ram. im told it is within spec. this is complete BS. I have ran some tests. what i have found id that the the compressor is turning off at the 50Degretemp, then re-engages at 52, then turns off at 50. it is very aperant that this issue is temp sensor or its a programming issue. the compressor is turning off way too early to make cold AC...... Im from Alberta and not happy at all with the AC performance. A 100K truck 1 ton should be able to keep us comfortable during the summer months.....
 
progatschnigg said:
So iv been following this issue for poor AC for 2 summers now. I have a 2019 3500 Limited. My AC is pretty pathetic. I have been to the deler 4 times now. Last week they did the so called TSB for housing and eveap replacement. The AC is only blowing 50 degrees...... I am experienced with AC as a tradesman.... I have 2 Toyotas that both blow at 39 Farenheight, they blow so cold i have to turn the blower down.
Now back to the Ram. im told it is within spec. this is complete BS. I have ran some tests. what i have found id that the the compressor is turning off at the 50Degretemp, then re-engages at 52, then turns off at 50. it is very aperant that this issue is temp sensor or its a programming issue. the compressor is turning off way too early to make cold AC...... Im from Alberta and not happy at all with the AC performance. A 100K truck 1 ton should be able to keep us comfortable during the summer months.....
Click to expand...
Im thinking if we can develope a new software or add-on that alters the compressor cycling this issue will be solved..... anyone figure out how to reprogram the AC cchip yet??
 
Will have to check the spec when I get back to work Monday, 134 does not work as well as R12.
 
brv10 said:
Will have to check the spec when I get back to work Monday, 134 does not work as well as R12.
Click to expand...
134 works fine. I found the AC shuts off the compressor when the evap sensor hits 4.3*C (39F). Vent temp eventually gets down to 8.5*C (47F), which is nice and comfortable.

Now I found better performance in my truck by slightly overcharging the system. I added about 1/4 more than specified. I also found if you put a 330kohm resistor in parallel with the evap sensor, you can lower vent temps by 2 degrees or so. Though I haven’t installed it yet to see if it freezes the evap…
 
CTF2019 said:
134 works fine. I found the AC shuts off the compressor when the evap sensor hits 4.3*C (39F). Vent temp eventually gets down to 8.5*C (47F), which is nice and comfortable.

Now I found better performance in my truck by slightly overcharging the system. I added about 1/4 more than specified. I also found if you put a 330kohm resistor in parallel with the evap sensor, you can lower vent temps by 2 degrees or so. Though I haven’t installed it yet to see if it freezes the evap…
Click to expand...
I been thinking of insulating the evao sensor, to fool it into running colder. I like your idea of a resister. Big question is how hard is it to locate the sensor or wiring? I havent looked at the HVAC box much yet. But yes the compressor cycles off to early. Nothing to do with R134a ect.
 
I'm also from Alberta, brought it to my dealer last fall after finding about TSB, they tested it said it's fine but they obviously couldn't test it properly as the outside temps were already cool. Will try again this summer. Last year in BC it was brutally hot and it could barely keep up
 
MEGA HO 3500 said:
I'm also from Alberta, brought it to my dealer last fall after finding about TSB, they tested it said it's fine but they obviously couldn't test it properly as the outside temps were already cool. Will try again this summer. Last year in BC it was brutally hot and it could barely keep up
Click to expand...
Yu0 same issue here..... i have a 08 tundra and a 2011 Sequoia. They both blow so cold you uave to turn the fan down.
This Ram is garbage.... for a 100K truck Limited. This is complete ********. All it needs to do is run the compressor longer and cycle at a colder temp. Makes me think they did this for fuel economy. Which is irrelavant on a 1 ton diesel. IDK...
 
CTF2019 said:
134 works fine. I found the AC shuts off the compressor when the evap sensor hits 4.3*C (39F). Vent temp eventually gets down to 8.5*C (47F), which is nice and comfortable.

Now I found better performance in my truck by slightly overcharging the system. I added about 1/4 more than specified. I also found if you put a 330kohm resistor in parallel with the evap sensor, you can lower vent temps by 2 degrees or so. Though I haven’t installed it yet to see if it freezes the evap…
Click to expand...
You need to get down to 32 or lower to freeze it up.
 
UPDATE,
So iv basically gave up with the dealership. Today I torn the glove box out and gained access to the evaporator sensor.
With the sensor in an ice bath it wwas reading about 8.5Kohms.
Sitting in ambient air, 20*Cish it was around 3.5Kohm
I ran a bunch of tests with the sensor removed. AC runs very cold, got the vent well past the freezing point. but clutch wont cycle of course.
This is a negative co-officient sensor, so temp goes down, resistance goes up. I determined if I need the Compressor to stay on longer, I would need to lower the resistance of the sensor. So I started hooking up some resisters in parallel to the sensor. Well after trial and error, ther A/C is the best its ever been. Cycles off at 39, back on at 41*F. I ended up using around 40K ohm of resisters. Tomorrow I will do some driving tests and get the actual resistance value.
But as of now I am super pumped with the results. I dont understand why warranty wasnt able to test the sensor/or replace it. I dont have the actual specs for the sensors values. But at least now I know how to fine tune the compressor cycling temps. Hope this helps everyone.
Pretty sad Ram and the dealership keeps saying it is working within spec..... 50*F vent temps is wayy off being good enough...
 
I can't find any specs for that anywhere.
 

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progatschnigg said:
UPDATE,
So iv basically gave up with the dealership. Today I torn the glove box out and gained access to the evaporator sensor.
With the sensor in an ice bath it wwas reading about 8.5Kohms.
Sitting in ambient air, 20*Cish it was around 3.5Kohm
I ran a bunch of tests with the sensor removed. AC runs very cold, got the vent well past the freezing point. but clutch wont cycle of course.
This is a negative co-officient sensor, so temp goes down, resistance goes up. I determined if I need the Compressor to stay on longer, I would need to lower the resistance of the sensor. So I started hooking up some resisters in parallel to the sensor. Well after trial and error, ther A/C is the best its ever been. Cycles off at 39, back on at 41*F. I ended up using around 40K ohm of resisters. Tomorrow I will do some driving tests and get the actual resistance value.
But as of now I am super pumped with the results. I dont understand why warranty wasnt able to test the sensor/or replace it. I dont have the actual specs for the sensors values. But at least now I know how to fine tune the compressor cycling temps. Hope this helps everyone.
Pretty sad Ram and the dealership keeps saying it is working within spec..... 50*F vent temps is wayy off being good enough...
Click to expand...
You mean 400kohm?

Using a 400kohm in parallel, I calculated the ac shut off temp at evap would drop about 3*F. Either I’m wildly off in my calc or you’re missing a zero?
 
CTF2019 said:
You mean 400kohm?

Using a 400kohm in parallel, I calculated the ac shut off temp at evap would drop about 3*F. Either I’m wildly off in my calc or you’re missing a zero?
Click to expand...
So i ended up adding 1 more 4.65Kohm resister the other day, cause the AC was too cold! Lol.
I measured the resisters i added, its at 29,000 ohm, or 29Kohm. The temp sesor on my workbench was at approx 3200ohms. With the parallel resisters added it measured around 2900ohms.
Getting 43*F vent temps
 
You sure?
Chrysler documentation was saying this.
1688013010213.png
That is what I based my calculations off.

I'm going to have to pull mine now and test on bench.
 
CTF2019 said:
You sure?
Chrysler documentation was saying this.
View attachment 59019
That is what I based my calculations off.

I'm going to have to pull mine now and test on bench.
Click to expand...
Iv been trying to find the evap sensor specs for a while now. When i uad it on my workbench it was around 20-23 degrees celcius. My fluke meter mesured 3200ohm approx. I did a ice bath test and it was approx 8000ohm. My truck is a 19. I uploaded a youtube video showing some resistance values. Title is, 2019 Ram A/C sensor hack for colder A/C.
I will probably purchase a new sensor, maybe mines out of spec. But for now its working great. Thx.
 

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progatschnigg said:
Iv been trying to find the evap sensor specs for a while now. When i uad it on my workbench it was around 20-23 degrees celcius. My fluke meter mesured 3200ohm approx. I did a ice bath test and it was approx 8000ohm. My truck is a 19. I uploaded a youtube video showing some resistance values. Title is, 2019 Ram A/C sensor hack for colder A/C.
I will probably purchase a new sensor, maybe mines out of spec. But for now it’s working great. Thx.
Click to expand...
Can you post the link to the video?
 
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