Automotive Air Conditioning Information Forum

I have a 2007 chrysler 300 touring with the single zone hvac control. I have put a new evaporator in ( it was leaking) a new compressor, and a new drier from four seasons on rock auto. Charged system with 12 oz cans of pure refrigerant no sealant. I also replace the expansion valve with a denso. Now the problem I am having I believe I had before replacing these components but when at idle on fresh air and max fan I have high suction pressure and slightly low high pressure. 49 psi low and 165 high. This was around 80 degrees ambient temp. I get around 58 degrees out of center vent. when I rev it up pressures and temps get better. i thought maybe the aftermarket ac compressor was not making enough flow or maybe I could try adjusting the expansion valve. Condenser is not blocked and fan motor operates fine. I am confident all blend doors are operating properly. i even pinched off heater core lines and had no change in temperature from center air vent.

Several aspects about your post suggest the following:

• Nowhere in your description do you mention evacuating the system. Before charging, the system MUST be evacuated to remove all traces of moisture and air.

• Charging from the small 12-ounce cans could result in an undercharge if you didn't weigh-in the refrigerant using an accurate charging scale. The small cans often contain less than 12 ounces and sometimes can't be emptied fully. Your system potentially could be a number of ounces short of a full charge.

• The Manifold Gauge Set hoses MUST be purged of all moisture and air before charging.

• Your testing conditions (engine idling, air intake open, etc.) don't place much of a heat load on the system, and the compressor isn't doing much of anything at idle speed. Testing should be around 1,800 RPM engine speed, windows and doors open, cabin blower on high, and A/C control set to "max."

• Is the aftermarket compressor new or rebuilt?

• I suggest not altering the TXV adjustment. It's set at the factory using sophisticated equipment.

• According to the specs that I have, your car takes 26 ounces net weight of R-134a and 5.5 fluid ounces of PAG-46.

I vacuumed the whole system including manifold gauge set for 30 minutes then let set for another 30 minutes for a leak test and it held a vacuum. I am certain all air was purged from my gauges. The compressor is new. I added as close as I could get to 26 oz which is 2 cans and another 2 oz. I added pag 46 oil to the system. You right about the heat load not being very high but I would think that since it isn’t high that the ac should be performing pretty well at idle which every vehicle I have messed with does. I think when I did my testing at was at 1500 rpm and got 42 psi low and maybe around 200 high and my vent temp was maybe 52 which is much better

First as a general rule, a mobile system will not predictably perform well at idle, as mentioned. If you find one that does, you are lucky.
You said the evap was leaking, so you replaced it. Why was the comp replaced? Did it grenade? If so the condenser must also be replaced, because it will be full of shrapnel and underperform. Was there any debris at the entrance to the expansion valve.
Please always give RPM and hi and lo pressures at every step you are testing as per John's advice.
Do the pressures look better and the vent temp improve if you continuously mist the condenser with a hose?

I replaced the compressor because the original was starting to get noisy. Wanted to replace it before it did grenade. Found no debris at the expansion valve. When I get a chance, I will mist the condenser and see what happens

dbtractor wrote: ↑Tue Aug 15, 2023 10:26 am I vacuumed the whole system including manifold gauge set for 30 minutes then let set for another 30 minutes for a leak test and it held a vacuum. I am certain all air was purged from my gauges. The compressor is new.

Very good. Were you able to pull a vacuum of 29.9 InHg or thereabouts?

dbtractor wrote: ↑Tue Aug 15, 2023 10:26 am The compressor is new.

Also very good. Rebuilt compressors have been known to give trouble after installation.

dbtractor wrote: ↑Tue Aug 15, 2023 10:26 am I added as close as I could get to 26 oz which is 2 cans and another 2 oz. I added pag 46 oil to the system.

I'm guessing that you're pretty close to the correct refrigerant charge specification. Do you recall how much oil you added to the system? Too much oil can negatively affect performance, too.

dbtractor wrote: ↑Tue Aug 15, 2023 10:26 am You right about the heat load not being very high but I would think that since it isn’t high that the ac should be performing pretty well at idle which every vehicle I have messed with does. I think when I did my testing at was at 1500 rpm and got 42 psi low and maybe around 200 high and my vent temp was maybe 52 which is much better

At 1,500 RPM, the high-pressure side suggests an ambient temperature of about 80°F. If so, the HP reading of 200 PSI looks about right. At 42 PSI, the low-pressure side indicates an evaporator temperature of about 46-48°F, too warm for the system to produce comfortable cabin air. Although you installed a Denso TXV, typically a high-quality part, it isn't unheard of to get a defective TXV once in a while. A 42-PSI reading on the low side implies that the TXV might be hanging open more than it should.

Pulled a vacuum down to 29 in hg my gauge may be reading 1 in hg off though. I added oil 2.5 oz to compressor and .5 to evaporator

Was the compressor empty of oil when you received it? You want a total of 5.5 fluid ounces of PAG-46 oil in the system, no more than that.

It had shipping oil so I drained it and added back to it. And accounted for what may have been left in the system

dbtractor wrote: ↑Tue Aug 15, 2023 1:03 pm Pulled a vacuum down to 29 in hg my gauge may be reading 1 in hg off though. I added oil 2.5 oz to compressor and .5 to evaporator

Vacuum looks good, although using a micron gauge like the pros do in addition to your Manifold Gauge Set would give a more precise reading. I shoot for around 500 microns, letting the vacuum pump run for at least one hour or as long as necessary to reach 500 microns. A reading of 500 microns is a nice, deep vacuum that's sure to remove all the undesirable air and moisture.

Replacing 2.5 ounces of oil into the compressor and adding 0.5 ounce to the new evaporator comes up short, I think. Presuming that 0.5 ounce remained in the condenser, an un-measurable amount in the lines and hoses, and nothing in the new R/D leaves you with only about 3.5 ounces in total. I would add another 2 ounces to this system, easily do-able without recovering and recharging it.