2011 Dodge Ram Poor AC Performance - Filter drier service

This is the second truck I have service in as many weeks that had the same issue. The first truck was actually building up enough pressure to discharge from the pressure relief port.
This truck is exhibiting poor AC performance and was 0.5 lbs low on refrigerant. The radiator had no build up or restriction and there were no visible leaks. When the pressures still weren't normal I was give the vehicle to diagnose.
I always like to look at the pressures to see if the compressor is working and also to see if the cooling fans are lowering the high side pressures adequately. This vehicle had the opposite problem when looking at the gauges. The high side pressure was too low and it actually dropped below the static pressure readings taken before start up.
The high side pressure dropped down to 70psi while idling with the AC turned on. The normal high side pressure is between 200 and 350 psi. Using the scan tool we can compare the pressure sensor readings at the compressor to the pressures measured at the high side service port.
What we found was a large discrepancy. This is caused by a restriction between the pressure sensor and the high side service port and the only thing between these two items is the AC condenser which happens to contain the filter/drier. Using the thermal imager we can determine where the blockage is and on this vehicle is was apparent that the blockage is at the filter/drier. After replacing the filter drier our pressures are much better but there is still some room for improvement. The condenser still has some slight restriction and the system will likely need replaced in the future.

[@scottschantz2553]

Nice job Chad. Appreciate your detailed instruction. Always look forward to your videos. Thanks.

[@boydduckett9240]

What? Someone actually FIXING a vehicle instead of throwing all kinds of parts at it? Nice job sir!

[@bartscave]

Great to see a new video from you Chad! You have been missed.

[@franciscodiez5825]

Great job Chad 👍 Thanks for sharing and bringing us along

[@PaulysAuto]

Great video Chad, great reason to confirm scan data to manual gauge readings...thanks for sharing this with us 🙏 😀 👍

[@KalebJTaber]

Thank you for sharing your knowledge. Super thorough and clear walk through, I appreciate your help!

[@packrat9433]

Very good video! Thaks a bunch! I am replacing my condenser and drier (Seperate on Dodge Ram) tomorrow. Thank you!

[@josephannable7771]

Great content. Amazing explanation

[@shamessun]

Thank you for this video

[@Alex-jm6fk]

You can have up to 30 degrees temp difference across the condenser in a normally operating system.

[@goatsgarage2635]

Dang after market bumper makes that easier lol

[@spelunkerd]

What an interesting look at the system, one not often seen. Do the scan tool pressure sensors measure absolute pressure, and the analog gauges measure relative pressure?

[@ThePracticalMechanic]

The service manual had very limited information about the AC pressure transducer so I’m not sure if it is actually a relative or absolute sensor. I will make sure to check the next one with the system at ambient pressure and see what pressure is displayed on the scan tool. I have a few more scheduled this week that will have the same sensor so I can verify. The gauges are a relative pressure for sure but on this older machine the calibration could be off enough to see the difference we saw when checking static pressures.

[@spelunkerd]

@@ThePracticalMechanic Thanks, Chad. Great to see you posting videos, I always learn a little more.

[@ThePracticalMechanic]

@@spelunkerd the 2006 dodge I just checked uses a relative pressure transducer and not an absolute. It reads 0psi on the machine and scantool but is 5 psi off when static pressure was around 100 psi. I will check the next one with my newer machine and see if the results are similar.

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