Tried Midas. Seeking a 2nd opinion.

[JohnHere]

When the shop said that the HS pressure was 400-plus PSI and the LS pressure was "retarded," was that condition noted with the A/C system running, or were those pressures recorded with the system and engine off?

[David]

DetroitAC and JohnHere, thank you so much for offering your insights.

The engine was on when the AC was pressure tested when it showed the high pressure.

Attached are 2 photos. The 1st photo shows the condenser fan line (if i got the right one?) at 94 degrees when the car hasn't been tuned on all day and cold. The 2nd photo shows the condenser fan line at 156 degrees after the car was turned on for 2 minutes.

Does this seem right?

[JohnHere]

The line on which you're measuring the temperature looks to be the liquid line or the high-pressure line. It should be warm-to-hot while the A/C system is running.

Is that the same line the shop changed out? In fact, some OT's are crimped permanently in position, requiring that the entire line be replaced. I'd sure like to know whether an OT is present inside the line, but that would require recovering the system and disconnecting the line to verify.

Do you have a Manifold Gauge Set of your own? If so, I'm curious as to what the pressures are now and whether you still get a reading in the "retard" zone on the low-side gauge and 400-plus PSI on the high-side gauge, backing up what the shop said. If you work on it yourself, be sure to wear sturdy PPE—eye, face, and hand protection—in case something lets go and releases the refrigerant under extremely high pressure.

[David]

No, the line I'm measuring is the lower condenser pipe.

DetroitAC said he thinks it's a clogged condenser filter and asked me if the very bottom of the condenser pipe gets cold. That's why I measured it before and after the car started. Is it supposed to get cold after the car starts and the AC runs for 2 minutes or is it supposed to get hot, like it did?

The liquid line is on top and near the firewall. It was completely replaced with a new one that already has an OT inside it.

Unfortunately I do not own any Manifold Gauges. I did buy an AC refill kit from Autozone last month and when I plugged it in, the arrow shot up to the red and I interpreted that as the system is over pressurized, which MIDAS confirmed. I had the car running and then plugged in the AC refill kit (didn't inject anything into the system) and the arrow was in the red and I also tested it with the car off and the again arrow jumped to the red.

Would really like to figure out if the condenser filter is clogged.

[tbirdtbird]

There is no condenser filter. The condenser itself acts as a filter because of its small passageways

Getting the temp of the condenser line when the car is off will be of no value.
Once the car and AC has been running about 15 min,(max fan, max cool, rpm at 1500, doors open) (shoot) take the temp of the pipe into and the pipe out of the condenser and we can compare those 2 temps.
When you take the pix, see if you can include in the shot where the red dot from the IR gun is showing. In these other 2 pix it is hard to tell exactly what part you are shooting

[JohnHere]

No, the line I'm measuring is the lower condenser pipe.

Right. That pipe is the liquid line or high-pressure (HP) line coming from the condenser, according to the A/C line routing diagram that I have for your truck.

The liquid line is on top and near the firewall. It was completely replaced with a new one that already has an OT inside it.

According to the same diagram, another liquid-line "extension," to which you refer, connects to the first line near the top of the radiator on the passenger side, which in turn connects to the evaporator inlet at the firewall. That entire two-piece HP line should be warm-to-hot up to wherever the OT is positioned. Just past the OT, the line should be cold. If it's hot all the way past the OT and into the evaporator, the OT is either missing or defective in some way.

Unfortunately I do not own any Manifold Gauges. I did buy an AC refill kit from Autozone last month and when I plugged it in, the arrow shot up to the red and I interpreted that as the system is over pressurized, which MIDAS confirmed. I had the car running and then plugged in the AC refill kit (didn't inject anything into the system) and the arrow was in the red and I also tested it with the car off and the again arrow jumped to the red.

DetroitAC mentioned earlier in the thread the possibility of the system being full of air or even nitrogen. Either one could have happened, although I think it's a remote possibility, especially for a competent shop paying close attention to what they're doing.

Two additional scenarios come to mind that could raise the low pressure (LP) into the "retard" zone on the LP gauge:
—Accidentally leaving both Manifold Gauge Set handwheels open and allowing the HP side to flow into the LP side, and
—Grossly overcharging the system.

There is no condenser filter. The condenser itself acts as a filter because of its small passageways.

tbirdtbird is correct. If the condenser is suspected of being clogged or partially clogged, it will have to be replaced.

Again, be careful working on this and be sure to wear your PPE (personal protection equipment). The evaporator, in particular, isn't designed to contain such high pressures and could suddenly disintegrate, releasing a cloud of HP refrigerant, oil, and shrapnel. Unprotected eyes and skin are especially vulnerable.

[DetroitAC]

For your reported condenser pressure of 400 psig +, yes it seems right, as in that is what your liquid line temperature should be for that much pressure. No, it's not right that you have that much pressure.

The condenser has it's own separate fan, it's on it's highest speed and running like hell when this is happening? I remember other AC development guys had one of these trucks with a fan set to run full speed all the time, sounded like it was trying to take off.

Good job checking that temperature, filter isn't the issue.

[JohnHere]

Here's another consideration:
Any compressor reed valves that are not fully sealing can allow HS-to-LS bleed-over, or reverse flow, as this system seems to be experiencing.

[David]

Thanks for the continued insights, fellas.

Would really like to treat myself to cold air and not pay for parts + install fees for things I don't need.

So what would be the next step toward process of elimination?

Many thanks!

[goslo]

I recall some of those Durango's and trucks would shut the compressor OFF at a stop light. All to save gas while you sweated the light out. Was told that was the way they were made.

400psi is way over juiced and could have a restriction. We need temp readings as others said at inlet and outlet of every device on the system. Some place the outlet on something is colder than the inlet. Also need low side pressures.

When reving the engine, do the gauge needles swing in relation to rpms? High side go up and low side down?

When you shut the engine down, does the system equalize steadily? Pressures should roughly match once equalized reaching close to ambient air temp.

Also think I read a recharge can kit with the hose and gauge was used? Those are a huge no-no. Air and moisture in that hose.