This will be a long story giving some info so bare with me.
My wifes Excursion (not diesel but same AC system as diesel equiped trucks) AC sucks *****, the POS has always thrown hot air at idle, but when going down the road or if I spray water directly on the condenser the AC throws it Ice cold to be specific 45°,checked it with a thermo gun at the vents.

Heres the stuff I replaced and did when my original AC compressor went bad (which also did the same thing.
1. AC compressor with the required oil capacity
2. Orifice filter tube
3. Reciver Drier
4. Fan clutch (OEM)
5. Flushed AC system
Installed gauges and used a vacuum pump, the vaccum held 29HG after 2hrs that I left it there, so I procedeed to add refrigerant making sure to purge the AC lines before adding the refrigerant into the system. Ac on full blast both rear and front, added the first 12oz can, noticed right away the AC clutch engaged and stayed engaged which I found odd looked at my gauges the low side was at 60PSI and the high side was at 360 psi on a 103° day????? Blockage???? But how? I flushed the entire AC system blew dryed it, condensor has no obstructions? so me being stubborn knowing I should stop I proceeded I added the required quanity of refrigerant ignoring the gauges( i was frustrated, after all I did it in direct sun light at 103° lol...) Well, giving a glimpse at the gauges low side at 110 and high side at 420 but as soon as I rev it at 3k or throw water at the condensor the low side goes down to 55 and high side at 200?

So question what going on here is my condensor blocked? Even though I flushed it the right way? How can I check if it is blocked? NEED HELP!!! my wife keeps driving my OBS (the AC is ice cold on that thing) and she is starting to like the power of it as well lol.....

 

Forgot to add the AC compressor is ingaged while Idling, and the drier is hot, but once water hits the condensor it starts to sweat and get iced. Idle with full charge low side 120, high side 420.

 

I would say there is something in the condenser. If you throw water on it and it cools down in the cab then the condenser is not converting properly. There is most likely a blockage within it or its clogged full of bugs and debris on the outside.

 

I'm going to echo Bakerbuilt here, there is an airflow problem currently. Spray the condenser down with simple green and wash it out (low pressure water) and check pressures again at idle.

 

The fins are clear of bugs, mud, etc. Thats why its got me stumped.

 

 

Hmm... Will have to check that out.

 

What's the charge amount for an Excursion? My truck was 2.5lb IIRC.

If you throw it in neutral while coasting down a hill will it cool well? Your pressures are getting within spec while at a higher RPM which is what makes me think it is an airflow issue at idle.

 

Never mind.....my lack of reading.

 

So it's a lack of idle airflow/cooling of the condenser. Fan clutch is new, but maybe defective. Does it have the fan shroud and not broken? I think there's also some seals or rubbers around the radiator & condenser to force the air to pull through the condenser. I don't know if it's possible on that engine, but verify the fan isn't inverted, pushing air instead of pulling it through.

If the pressure switches were inverted it might stop the compressor, but wouldn't change your pressures with the compressor engaged.

 

Can you hear the fan clutch engage? My pressures increase when mine idles also. Going to tear into it soon. Was thinking on changing the orifice tube to the 38639. Any buddy done that here? Suppose to drop the temp out the ducks. But don't run it on high below 80 temp out side. Haven't made my mine up yet, but it gets hot out here in the summer months.

 

So no buddy has run the 38639 tube?

 

From what I'm finding online that condenser is a parallel flow not a tube and fin. It may have some blocked tubes making only a portion of the heat exchanger carry all of the hot refrigerant vapor flow. Parallel flows wont clear totally like a the older inefficient tube and fin design condenser. The flush fluid takes the path of least resistance which is the open tubes so clogged tubes have very little chance of being cleaned out.
The density of the water can pull out a lot of heat which is shown by the pressure drop you are seeing.
A cheap IR point and shoot thermometer should point out the active (hot) areas where flow is and cool areas where there is no flow and no heat being exchanged if good airflow is verified top to bottom.

 

Did you get this figured out? Would like to here what you found? I have a similar problem. Just changed the orifice tube and recharged. It's cooler but not enough. My fan works, at least it's pulling. Going to check between the radiator and see what that looks like. Need to find my gun to check temps on the condenser.

 

Still havent gotten around to it, but ill update as soon as I look into it.