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Discussion Starter · #1 ·
With the other issues I had I kind of forgot about this one.

AC seems to work ok until it gets 90's+, then blinks out. Compressor not running.

With the AC switch on (when compressor is not turning on);

pressures about 115psi L&H.

FORScan showing with (ac working or not);
"ACC On Air conditioner compressor cycling switch
ACP OPEN (OK) A/C pressure switch
WAC/ACCR On Air conditioning clutch".
Does this mean the compressor clutch should be engauged but is not?

When the compressor was turning on, at around 1800rpm, I believe the high side was going up to about 375+or- (hard to tell through the windshield) & the low was dropping to about 20-25 then cycling off.
 

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I would look for a leak because I think when the AC is working and the temperature outside is hot it makes the AC work harder so you may be low on Freeon. If you have a stain or oily dirt on a hose or condenser you have a leak.
 

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Every AC system I looked at has a dual pressure switch and a safety pressure switch that goes inline with the wiring to the clutch. So if high pressure gets too high it will remove power to the clutch no matter what the HVAC control or ECU says. Is the clutch fan working? Is the condenser clogged, pressures at idle???
 
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High pressure switch cuts the system off at about 350, so sounds like you may have too much charge or the condenser coil is not getting air flow -- bent fins, bug guts, fan not working

Get your hand on the line just in front (up stream) of the orifice -- will be about ambient + 20 degrees on the up stream side, and cold on the down stream side -- if the up stream side is much hotter, then there is a problem with the condenser

Your truck have the factory electronic fan clutch ? -- should see a speed increase when the AC is turned on, and the truck is parked
use a brick, 2x4, or other means to hold the throttle to about 1500 -- so you can watch the gauges under the hood and check temperatures
 
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Discussion Starter · #5 ·
I have the 7.3 fan clutch adapter.

I may have a couple of issues here, not sure. It is possible that I have an incorrect charge & wondering if there is a restriction in the orifice.

Not sure either of those are the reason that the compressor will not engauge (hot ambient temps & hot engine 195ish temps) when it appears that all the sensors are telling it to come on.

I put a jumper on the low pressure switch, just to make sure that wasn't the issue.

It seems to function ok (blowing about 35-40 below ambient temps) until it has been running for 30 minutes or more, when ambient temps are 90's or close.

I may swap the relay with a different one to see if that changes anything, what stinks is that when it does it the engine bay is so stinkin hot makes it hard to check things.
 

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Discussion Starter · #6 ·
I have checked the air gap on the compressor clutch, with the feeler gauge in a little over 1", it has .035 on one side & .040 on the other. About 1/2" in is somewhat more.

Is this enough out of specs to cause no clutch engaugement when hot?

Does the shroud have to come loose from the block to give clearance for the clutch to come out to change shims?
 

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The clutch air gap clearance specification is 0.35-0.75 mm (0.014-0.030 in)
The A/C pressure cut off switch opens at 435-475 psi

I have seen excessive clearance cause your problem but usually the clutch engages and then releases when the gap is excessive, gets worse when running for a period of time... so maybe it's an issue. I like the suggestions about the high pressure elevating due to the fan or poor airflow through the cooling stack. The time to diagnose something like this is when the concern is present.
 

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The clutch face does not wear evenly, so measuring with a feeler like that will not work well on a used clutch -- it does seem like your clearance is excessive ,and can probably take all the shims out -- measuring the travel of the clutch plate is a more accurate method

The magnetic pull of the clutch is greater when cold, and as things heat up if the clearance is too much, the clutch may slip or not be able to engage at all
 

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Discussion Starter · #9 ·
I pulled the shim, there was only 1. It was a .035, I filed it down a bit & reinstalled. The whole family is out of town & this is my only ride so I couldn't wait on a shim kit. I will see how it does tomorrow.
 

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Discussion Starter · #10 ·
I filed the shim down about .005'ish, so far so good on the compressor engaging. Drove about 50 miles in 90+ temps & it did not turn off.

There was some oil/grease on the friction surfaces as well, I cleaned them off. Not sure if it is compressor oil or bearing grease but either way it will probably require a compressor in the future.
 
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