I was wandering if anyone coud tell me how much freon the system holds, also my low side pressure is around 36 pounds and high side was 132 pounds. The needle on the high side was bouncing just a little bit also. The wes chked on a 75-80 degree day. I was only cooling to 59 degrees out of the duct inside. the lines going to the dryer are also freezing and the line comming out of the dryer is also freezing. any ides i would really be thankful thanks guys oh also its a 2003 2500hd thanks again

Moving to Interior section...

Your pressures are low. I think they should have about 3-4 pounds of 134a. Your lines are freezing up because your low on freon. Ithink your psi's should be closer to 200 hi and 70 lo.

Per my Helms manual, a dry system takes 1.6lb of R-134A. That is after being on a vacuum pump to remove all previous refrigerant and any air that may have gotten into the system.

This chart may be of help if you have gauges. Readings are taken with the windows open, AC set to the coldest setting, Fan on MAX and Recirc ON, Dash vents selected and all open, engine at idle.

After re-reading the original post, make sure you have good air flow through the evaporator because your pressures don't look that far off.. Do you have in-cab air filters on your truck? If so, may need replaced. Otherwise, may be blocked or clogged evaporator. If the freon can't pick up heat from the air it will frost back. If you allow frost to form all the way back to the compressor, you could damage the reed valves by liquid slugging.

On my 02' I believe the ac took approx 1.85 lbs of 134. This was for a crew cab with no rear air.

well I let the freon out, thought i would start new. Changed the master oriface while i was there. It had metal in it! sucked the system down chraged it with freon best i can get is 53degrees out of the center vent on an 80 degree day. I think im just going to replace the drier and compressor, flust the condensr and evap. I tired of messing with it and cant get any help from the dealerships. They tell me a 20 degree dif from th eoutside air is fine.

The chart above is what will tell you if the system is within specs, a general rule of thumb is 20 deg diff, but the chart will tell you what its range is. I have replaced tons of compressors in those trucks, most concerns start out as a a/c belt coming off or squealing type of concern.

The chart above is what will tell you if the system is within specs, a general rule of thumb is 20 deg diff, but the chart will tell you what its range is. I have replaced tons of compressors in those trucks, most concerns start out as a a/c belt coming off or squealing type of concern.

You have seen this on a diesel. I replace a a lot for compressors on gen 3 engines for a squeeling or belt comming off, but never a diesel.
Acording to GM your max discharge temp at those ambiant air temps. will range from 63 dergrees at low humitity to 68 degrees at high humitity. although i usually see temps in the low 40's on properly running a/c systems. there is a bulletin that may apply to you.

Subject: Poor A/C Performance -- A/C Will Not Blow Cold Enough (Perform A/C System Checks, Replace Accumulator if Necessary)


Models: 2002-2004 Chevrolet Silverado

2002-2004 GMC Sierra

with 6.6L Diesel Engine (VINs 1, 2 -- RPOs LB7, LLY)

and Denso A/C Compressor




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This bulletin is being revised to add part numbers for the hose, bracket and insulator to the Parts Information. Please discard Corporate Bulletin Number 02-01-38-007B (Section 01 -- HVAC).


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Condition
Some customers may comment on less than desirable A/C performance, especially when the ambient temperature is above 32°C (90°F).

Correction
Perform the following A/C system checks and replace the accumulator with P/N 89018601, if necessary. This new accumulator requires the accumulator bracket, the accumulator insulator and the A/C suction hose to be replaced also.

• Check for A/C system leaks.

• Check the A/C system for proper refrigerant charge. This requires recovering the refrigerant to determine charge in system. Refer to Refrigerant Recovery and Recharging in the HVAC sub-section of the Service Manual.

• If no leaks were found and the A/C system is charged to specification, replace the accumulator using the procedure listed below.

If normal diagnostics do not lead to a correction, then perform the following A/C system checks.

Re-calibrate the actuators. Refer to Recalibrating Actuators in the HVAC System - Manual/Automatic sub-section of the Service Manual (SI Document ID #904666).
Inspect the lower A/C condenser deflector for proper installation. The deflector should be positioned at the lower part of the condenser and extend forward into the top of the front bumper and below the two fresh air intake holes.
Check the engine cooling fan clutch for proper operation. Refer to Fan Clutch Diagnosis in the Engine Cooling sub-section of the Service Manual (SI Document ID #774320).
If the vehicle is equipped with a front license plate, inspect for proper installation. If the license plate bracket is installed upside down, it will block part of the two fresh air intake holes in the bumper. When the license plate bracket is installed correctly, the writing on the back of the bracket will be upside down.
Inspect for material between the radiator and condenser. Remove the top plate to confirm that there is no restriction. A radiator front filled with material will decrease condenser performance.

Some improvements have been found by lowering the A/C charge from 0.82 kg (1.8 lbs) to 0.73 kg (1.6 lbs).
Check the low pressure cycling switch for proper operation. The low pressure switch opens at 172-234 kPa (25-34 psi) , which stops compressor operation and closes when the low side pressure reaches 276-310 kPa (40-45 psi). This enables the compressor to turn back on.
Important: Compressor clutch engagement cannot be used to determine the status of the low pressure switch. The low pressure switch is one of several inputs to the HVAC control module for A/C request authorization. A/C request is one of several inputs to the powertrain control module (PCM) that control A/C compressor clutch engagement.

Using a scan tool to monitor low pressure switch status while monitoring the low side pressure with the ACR 2000 at the service port and watch the pressure at which the switch opens/closes is imperative to successfully diagnosing the switch.


If the A/C performance has not improved after performing the above steps, replace the accumulator with P/N 89018601, using the procedure listed below. This new accumulator also requires the accumulator bracket, accumulator insulator and A/C suction hose to be replaced.