Hello- if someone would be interested in helping me solve an AC problem I’m experiencing in my 2005 Ram 2500, I’d appreciate it. I can fill you in on more of the details via PM. Thanks in advance.

1. System was vacuumed and held -30 for 10 minutes.

2. Filled to OEM capacity with 134a

3. Reman compressor- clutch engages and condenser fan turns on when switched to AC. Recirc door works, blend doors responds to input- dual zone controls- on heat zones get hot on cold- zone become like warm.

4. Laser temp of evap core- 78* with AC on, laser dash temp of vents- 78* w/ AC on

5. Accumulator freezes up when charging- high side line after the expansion valve also freezes up but no coldness enters or exits the evap core. BUT both lines to the core have been disconnected and compressed air blows through freely with no apparent restriction.

6. AC line to and from the compressor are NOT hot when AC compressor clutch is running.

7. Hooked gauges to high and low side and ran compressor. Both read 110 with compressor off- but BOTH increased to 125-130 with compressor cycling on.

Bottom line- system is charged and responds when AC is called for but evap core is not getting cold and consequently there is no cooling in the cab.

Any ideas???

System pressure is ambient temp dependent, but regardless, your low side pressure is way high and your high side is too low.

Is the AC condenser fan coming on?

Did you add additional oil to the system?

Condenser fan comes on right as the compressor clutch engages. All happens after AC button is pressed inside the cab- like it should. I did all a small can of oil when I changed the compressor. Ambient temp during the gauge reading was 72 degrees.

How much is a small can

I believe it was 3 oz combo of oil and R134. It was for compressor lubrication.

I just replaced the compressor on an 07 Civic hybrid this past weekend. The compressor I used came precharged with oil and the instructions clearly stated to add no oil to the system.

Now days the systems are build to "just enough" specs and you can get into trouble adding too much oil, or freon for that matter.

I still haven't figured mine out on the. 2015 2500 5.7 hemi. When you first start it up in the morning, it will run cold for 15 minutes then gradually go away to warm. This happens EVERY time! Once warm it will not get cold again until the next morning after sitting all night. My dealer techs couldn't figure it out, did the dye thing, charged it twice, and now it is in the shop until they figure it out...

Orifice tube system correct.

Change it ?

pretty sure you have a partially clogged condenser. run the a/c and feel the condenser core, it should be warm/hot from top to bottom. any cold spots and there's your problem. BTW, I have seen this before. iapco103

Roger on checking out the condenser core- it’s not warm/hot at all. Which I don’t understand because the gauges change pressure when the compressor is on which means it’s at least getting to the high side fitting…orifice tube is original but I will try a new one if that is a possibility of being the problem.

Correction- initially the top hose and upper half of the condenser get hot then after a few minutes they are just warm….no significant heat below the middle of the condenser when running.

You mentioned that the pressure is 110 when the system is off. That is about right. That is the pressure at which the the low side and high side equalize at. 110 is fine. Your cooling fan turns on when the system is turned on, which is fine.
If both the low side and high side stay at 125 - 130 then you have a restriction in the line somewhere. Low side should be 30 to 40 psi for good cooling. Most common restriction point is at either the expansion valve or where you have the orifice tube at.
Most common place is at either the expansion valve or where you have the orifice tube at. Both of those tend to get mucked up after a while and cause the system feel warm.
I don't know if your system uses an expansion valve or orifice tube, but this is what I would check first.
So, what I would do is check the expansion valve or orifice tube. If they are mucky or have a any deposits on them replace them. Then, blow out all the lines before switching out the orifice tube or exp valve.
Vacuum down for about 30 min and recharge again.

Your system is equalized,compressor & exp.valve or orifice tube separate the high & low,possible bad replacement compressor?

Thank you for your insight. I plan to buy a new high side line that includes a new orifice. Hopefully that does the trick. When I replaced the compressor it makes sense that it may have become occluded due to debris in the system.

This can be normal when charging to the high side. The cold is created when the refrigerant expands. It is common to get cold at the fitting it is being put in at as it expands into the empty system. It is better to charge through the low side because if the pressure on the high side goes up as it should, It can prevent the refrigerant from moving from the can to the system and the can could rupture if the pressure gets too high.



Only one should be hot. The other will be cool. Hot is high pressure going to the condenser at the front of the car. Cool is the low pressure intake from the evaporator.



Are you closing the high side pressure gauge valve? The gauge manifold has a knob on each side. You should close them unless charging and then only the low side valve. If they are both open the high pressure can migrate to the low side negating the system.

When a gas is compressed it get hot. When it expands it gets cold.
The orifice tube/Expansion Valve is basically a small hole (restriction) with High Pressure refrigerant on one side. The refrigerant escapes through the small hole and the pressure drops creating cold in the evaporator.

If the High and low pressure is too close to each other, then you have a bad compressor not creating pressure or the orifice tube/expansion valve is defective and not creating a restriction and it will not build pressure.
If the Orifice tube is clogged it will build very high pressure on the high side and very low pressure on the low side.


You mentioned you added 3 oz of oil. You also mentioned a remanufactured compressor. Some will come with oil and some will not. Did you check the compressor for oil?

I do not know the specs off the bat but that system should use about 6 oz of oil. check the label under the hood. You need to be sure that the oil is correct type and amount.

You said the compressor was a reman unit, how did the old one fail? A bad clutch will not send trash into the system but if the compressor was making noise then it was coming apart inside and probably sending metal filings into the system.
When you replaced the compressor what color was the oil coming out of the system? Clear or green is okay, Green is a dye some people use to find leaks. Grey, black or any other color is metal in the system and you have to do a serious cleaning/replacement of parts.

When replacing the compressor you should do the following.
Flush the hoses and evaporator. Take note of the oil coming out.**
Replace the orifice tube/expansion valve.
Replace the filter/dryer/accumulator.
If you have the modern style condenser that can not be flushed replace it otherwise flush the evaporator and the condenser.

How many of those things did you do when you replaced the compressor?

** If the oil shows metal filings you are bettor off replacing the evaporator & condenser unless you have a professional flushing machine.

Thanks for the info- upon retesting with the valves on the gauges closed when the compressor came on the high side went to 125 and the low side went to negative 20-30….when I shut the compressor off and let the truck idle the high side retreated to 110 and the low side rose to over 75…the high side line from the orifice froze up the whole was to the evaporator and warmed up one the compressor was shut off.

Negative pressure is clogged orifice tube or expansion valve.

The correct pressures will be dependent on the temperature.

Here is a chart.

Good catch. I didn't catch the word negative.

Yes extreme high and low pressures indicate a clogged orifice tube or expansion valve. Zero or Negative low is an extreme.

Got it. I’ll put a new one on and let you know what happens. Thanks