Automotive Air Conditioning Information Forum

I have a 2011 Ram 2500 with a 6.7. When the AC runs for a while driving I can hear the compressor when it's on inside the cab it almost sounds like a hydraulic pump. Currently, my Low side is around 30 and my high is about 300. THe A/C works perfect otherwise.

What does it sound like with hood open and you standing there.
Is this at all RPMs
Any work recently or ever done?
New complaint?
Ambient?
How long does the AC have to run before the noise shows up

More noticeable at 1200 rpm+ Cant really hear it outside of the vehicle every component of the AC system was replaced last year Noise has been there since before that work was done. 100*f Most of the time it can be noticed within 5 mins of running.

If you cannot hear it outside the vehicle with the hood up, then I suspect it is not the comp, but rather a harmonic from something, perhaps not even an AC component.
Especially since it did it before all the work was done.
By the statement "everything was replaced" we assume that includes the comp??

Does the sound disappear if you switch the AC off while on the road?

Can we assume Cummins... no chance of a harmonic from the injector pump??

Mileage?
Is the rubber of the harmonic crank balancer shot?

Could be a harmonic issue. but it's definitely the from the AC. It cycles on and off and when it does is the only time you hear the noise. When its constantly running to get to evap temp you can hear it the whole time essentially. Truthfully though with how loud the cummins is it would mask the sound.

So, again, is comp new also?
This is important because if sound was there with both old and new comps, then I can't see how 2 different comps could both be to blame

Would love to have Ice weigh in on this one...

CComp is a new Oreilys unit.

In looking at the parts diagram for your truck's A/C system, I don't see any in-line mufflers pictured on any of the metal lines and hoses. These mufflers, which look like small cylinders or cans, are intended to dampen the compressor's pumping sounds on many vehicles.

Apparently, the design engineers (and bean counters) left the mufflers off this system—maybe because of the diesel engine's higher noise level—reasoning that any compressor sounds wouldn't be heard anyway.

I'm beginning to think that the noises you're hearing, ostensibly coming from the compressor, are just the "nature of the beast," especially since the system is working well otherwise.

I sure hope so I thought this is what lead to my old compressor failure but I’m pretty sure it was the bad fan clutch. I had a couple of blow off before failure because of super high pressures

admorrow wrote: ↑Tue Jun 21, 2022 10:18 pm I sure hope so I thought this is what lead to my old compressor failure but I’m pretty sure it was the bad fan clutch. I had a couple of blow off before failure because of super high pressures

Poor condensing due to a bad fan clutch definitely will drive-up the high-side pressures and strain the compressor. At 100F ambient, the high side at 300 PSI is a little higher than I'd like to see but don't think it's anything to worry about.

Did you test the pressures at or about 1,500 RPM engine speed, A/C on max or "recirc," blower on medium, and windows open? If not, I'm sure the high side will come down a bit if you do.

Once you're on the road, the high side should moderate due to the increased airflow across the condenser.