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Every once an awhile, the A/C temp AND airflow diminish.
I'm suspecting icing on the evap because both problems are similtainous.
If it were a airflow damper, (I believe they're elect not vaccum on the 2500HD), then just airflow would diminish, but the air temp would remain the same.
I loose about 70% temp and airflow.
Anyone tackle this problem? Only happens in extreme heat, then resumes to normal airflow and temp, after parking the truck a spell, and not always happens.
I understand several Pontiac modles have the same phenomina.
I suspect icing on the evap.
Anyone have a take?
Thanks for any imput.
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happens to my HD too......once I stopped and let it sit.....big puddle underneath......my guess ice....don't know why yet...
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happens to my HD too......once I stopped and let it sit.....big puddle underneath......my guess ice....don't know why yet...
I suspect that too, and if it's the prob,, then we can find a solution.
I'm not real hep with R134, but I know some genius wrenches that are.
I'll look into how it can be adjusted to not ice up.
Several methods depending on the refrigerant gas metering device, all simple depending of the type of metering, or a simple thermistor adjustment/location if it has one.
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Do you run it in recirc mode or fresh air mode?
Recirc turns it into an ice maker. Fresh air keeps ice down to minimum.
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Do you run it in recirc mode or fresh air mode?
Recirc turns it into an ice maker. Fresh air keeps ice down to minimum.
I run it in fresh most of the time, and it still does it. Around town it doesn't usually happen, only out on the highway for awhile (seems like anyway). Real hot days it happens more often.
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I run it in fresh most of the time, and it still does it. Around town it doesn't usually happen, only out on the highway for awhile (seems like anyway). Real hot days it happens more often.
Ditto here too,, gotta be ice.
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IF you have a diesel, you might try this bulletin.......
Poor A/C Performance - A/C Will Not Blow Cold Enough (Perform A/C System Checks, Replace Accumulator, If Necessary) #02-01-38-007C - (Jul 27, 2004)
Poor A/C Performance -- A/C Will Not Blow Cold Enough (Perform A/C System Checks, Replace Accumulator if Necessary)
2002-2004 Chevrolet Silverado
2002-2004 GMC Sierra
with 6.6L Diesel Engine (VINs 1, 2 -- RPOs LB7, LLY)
and Denso A/C Compressor
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).
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.
Accumulator Replacement
Remove the suction hose mounting bolt from the A/C compressor.
Remove the suction hose from the compressor.
Remove the suction hose nut from the accumulator.
Remove the suction hose from the accumulator.
Remove the evaporator tube nut from the evaporator.
Remove the evaporator tube from the evaporator.
Disconnect the electrical connector from the A/C low pressure switch.
Remove the nut from the evaporator fitting.
Remove the accumulator bracket nut from the retaining stud.
Remove the accumulator.
Remove the retaining bracket bolt. This bolt must be reused for the new bracket.
Remove the insulator. One half of the insulator must be reused.
Install the new insulator and one half of the old insulator onto the new accumulator.
Install the new retaining bracket and bolt to the accumulator. Do not tighten at this time.
Add the PAG oil directly into the new accumulator that was removed during the recovery process plus an additional 90 ml (3 oz).
Install the new accumulator.
Install the accumulator bracket nut.
Tighten
Tighten the nut to 9 N·m (80 lb in).
Tighten the retaining bracket bolt.
Tighten
Tighten the nut to 10 N·m (89 lb in).
Install the nut to the evaporator fitting.
Tighten
Tighten the nut to 16 N·m (12 lb ft).
Install the evaporator tube to the evaporator.
Install the evaporator tube nut to the evaporator.
Tighten
Tighten the nut to 16 N·m (12 lb ft).
Install the new suction hose to the accumulator.
Install the suction hose nut to the accumulator.
Tighten
Tighten the nut to 16 N·m (12 lb ft).
Connect the electrical connector to the A/C low pressure switch.
Install the new suction hose to the compressor.
Install the suction hose mounting bolt to the A/C compressor.
Tighten
Tighten the bolt to 16 N·m (12 lb ft).
Parts Information
Part Number
Description
89018601
Accumulator
15136596
Hose Assembly
15136597
Bracket
10372792
Insulator
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation
Description
Labor Time
D4702*
HVAC System Check
0.6 hr
Add:
To Replace Accumulator
0.4 hr
Add:
To Recover/Recharge A/C System
0.5 hr
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I suspect you have a faulty cycling switch though..........
Air Conditioning (A/C) Inoperative/Intermittent, A/C Blows Warm Air (Replace A/C Low Pressure Cycling Switch) #03-01-39-007 - (May 29, 2003)
Air Conditioning (A/C) Inoperative/Intermittent, A/C Blows Warm Air (Replace A/C Low Pressure Cycling Switch)
2003 Cadillac Escalade, Escalade EXT, Escalade ESV
2002-2003 Chevrolet TrailBlazer, TrailBlazer EXT
2003 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2002-2003 GMC Envoy, Envoy XL
2003 GMC Sierra, Yukon, Yukon XL
2002-2003 Oldsmobile Bravada
2003 HUMMER H2
Condition
Some customers may comment that the A/C system is intermittently inoperative or blows warm air.
Cause
An intermittent inoperative (open) A/C low pressure cycling switch may be the cause. This is an intermittent condition and temperatures may play a critical role if the vehicle is in the failed mode or operating as designed.
Correction
Follow the diagnosis and service procedure below to correct this condition.
Park the vehicle inside or in the shade.
Open the windows in order to ventilate the interior of the vehicle.
If the A/C system was operating, allow the A/C system to equalize.
Turn OFF the ignition.
Open the hood and install fender covers.
Caution:
Avoid breathing the A/C Refrigerant 134a (R-134a) and the lubricant vapor or the mist. Exposure may irritate the eyes, nose, and throat. Work in a well ventilated area. In order to remove R-134a from the A/C system, use service equipment that is certified to meet the requirements of SAE J 2210 (R-134a recycling equipment). If an accidental system discharge occurs, ventilate the work area before continuing service. Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.
For personal protection, goggles and gloves should be worn and a clean cloth wrapped around fittings, valves, and connections when doing work that includes opening the refrigerant system. If R-134a comes in contact with any part of the body severe frostbite and personal injury can result. The exposed area should be flushed immediately with cold water and prompt medical help should be obtained.
Notice:
R-134a is the only approved refrigerant for use in this vehicle. The use of any other refrigerant may result in poor system performance or component failure.
To avoid system damage use only R-134a dedicated tools when servicing the A/C system.
Use only Polyalkylene Glycol Synthetic Refrigerant Oil (PAG) for internal circulation through the R-134a A/C system and only 525 viscosity mineral oil on fitting threads and O-rings. If lubricants other than those specified are used, compressor failure and/or fitting seizure may result.
R-12 refrigerant and R-134a refrigerant must never be mixed, even in the smallest of amounts, as they are incompatible with each other. If the refrigerants are mixed, compressor failure is likely to occur. Refer to the manufacturer instructions included with the service equipment before servicing.
Install the J 43600 ACR 2000 Air Conditioning Service Center.
Important:
The ambient temperature must be at least 16°C (60°F) .
Do not induce additional air flow across the front of the vehicle during the test.
Record the ambient temperature displayed on the J 43600.
Record readings of the low and high side STATIC pressures. The pressures should be within the specifications listed below.
- Above 16°C (60°F): 345 kPa (50 psi)
- Above 24°C (75°F): 483 kPa (70 psi)
- Above 33°C (90°F): 690 kPa (100 psi)
- If the static pressures are within specification, continue with Step 12.
- If the static pressures are NOT within specifications, refer to Leak Testing (SI Document ID# 1141201).
Apply the parking brake.
Place the transaxle/transmission in PARK.
Start the engine.
Turn on the A/C system.
Inspect the A/C compressor to see if it is operating properly.
If the compressor is not operating as designed, tap on the low pressure cycling switch (2) with a small hand tool. The compressor should start operating correctly.
If the compressor does not operate correctly after tapping on the low pressure cycling switch (2), disconnect the switch and jumper the lower pressure cycling switch connector with a fused jumper. If the compressor still does not operate properly, refer to HVAC Compressor Clutch Does Not Engage diagnostic in SI.
Important: DO NOT USE A/C low pressure cycling switch, P/N 15035084 on the vehicles listed above.
If the compressor does operate correctly after tapping on the switch or jumping the low pressure cycling switch connector, replace the low pressure cycling switch (2), P/N 89040362. Refer to Air Conditioning (A/C) Low Pressure Switch Replacement in SI.
Perform the Air Conditioning (A/C) System Performance Test in SI.
Disconnect the J 43600 ACR 2000 Air Conditioning Service Center.
Remove the fender covers and close the hood.
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Every once an awhile, the A/C temp AND airflow diminish.
I'm suspecting icing on the evap because both problems are similtainous.
If it were a airflow damper, (I believe they're elect not vaccum on the 2500HD), then just airflow would diminish, but the air temp would remain the same.
I loose about 70% temp and airflow.
Anyone tackle this problem? Only happens in extreme heat, then resumes to normal airflow and temp, after parking the truck a spell, and not always happens.
I understand several Pontiac modles have the same phenomina.
I suspect icing on the evap.
Anyone have a take?
Thanks for any imput.
You are correct in your assumption. Evap. is likely icing up. I'm not a GM tech. so don't know their specific problems, but of the bulletins posted I would say replace the accumulator for possible moisture in system. An open cycling switch would not allow the compressor to engage, which is not your problem. A cycling switch that didn't cut off compressor at 22.5 lbs. could cause your symptom though.
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I suspect you have a faulty cycling switch though..........
Air Conditioning (A/C) Inoperative/Intermittent, A/C Blows Warm Air (Replace A/C Low Pressure Cycling Switch) #03-01-39-007 - (May 29, 2003)
Air Conditioning (A/C) Inoperative/Intermittent, A/C Blows Warm Air (Replace A/C Low Pressure Cycling Switch)
2003 Cadillac Escalade, Escalade EXT, Escalade ESV
2002-2003 Chevrolet TrailBlazer, TrailBlazer EXT
2003 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2002-2003 GMC Envoy, Envoy XL
2003 GMC Sierra, Yukon, Yukon XL
2002-2003 Oldsmobile Bravada
2003 HUMMER H2
Condition
Some customers may comment that the A/C system is intermittently inoperative or blows warm air.
Cause
An intermittent inoperative (open) A/C low pressure cycling switch may be the cause. This is an intermittent condition and temperatures may play a critical role if the vehicle is in the failed mode or operating as designed.
Correction
Follow the diagnosis and service procedure below to correct this condition.
Park the vehicle inside or in the shade.
Open the windows in order to ventilate the interior of the vehicle.
If the A/C system was operating, allow the A/C system to equalize.
Turn OFF the ignition.
Open the hood and install fender covers.
Caution:
Avoid breathing the A/C Refrigerant 134a (R-134a) and the lubricant vapor or the mist. Exposure may irritate the eyes, nose, and throat. Work in a well ventilated area. In order to remove R-134a from the A/C system, use service equipment that is certified to meet the requirements of SAE J 2210 (R-134a recycling equipment). If an accidental system discharge occurs, ventilate the work area before continuing service. Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.
For personal protection, goggles and gloves should be worn and a clean cloth wrapped around fittings, valves, and connections when doing work that includes opening the refrigerant system. If R-134a comes in contact with any part of the body severe frostbite and personal injury can result. The exposed area should be flushed immediately with cold water and prompt medical help should be obtained.
Notice:
R-134a is the only approved refrigerant for use in this vehicle. The use of any other refrigerant may result in poor system performance or component failure.
To avoid system damage use only R-134a dedicated tools when servicing the A/C system.
Use only Polyalkylene Glycol Synthetic Refrigerant Oil (PAG) for internal circulation through the R-134a A/C system and only 525 viscosity mineral oil on fitting threads and O-rings. If lubricants other than those specified are used, compressor failure and/or fitting seizure may result.
R-12 refrigerant and R-134a refrigerant must never be mixed, even in the smallest of amounts, as they are incompatible with each other. If the refrigerants are mixed, compressor failure is likely to occur. Refer to the manufacturer instructions included with the service equipment before servicing.
Install the J 43600 ACR 2000 Air Conditioning Service Center.
Important:
The ambient temperature must be at least 16°C (60°F) .
Do not induce additional air flow across the front of the vehicle during the test.
Record the ambient temperature displayed on the J 43600.
Record readings of the low and high side STATIC pressures. The pressures should be within the specifications listed below.
- Above 16°C (60°F): 345 kPa (50 psi)
- Above 24°C (75°F): 483 kPa (70 psi)
- Above 33°C (90°F): 690 kPa (100 psi)
- If the static pressures are within specification, continue with Step 12.
- If the static pressures are NOT within specifications, refer to Leak Testing (SI Document ID# 1141201).
Apply the parking brake.
Place the transaxle/transmission in PARK.
Start the engine.
Turn on the A/C system.
Inspect the A/C compressor to see if it is operating properly.
If the compressor is not operating as designed, tap on the low pressure cycling switch (2) with a small hand tool. The compressor should start operating correctly.
If the compressor does not operate correctly after tapping on the low pressure cycling switch (2), disconnect the switch and jumper the lower pressure cycling switch connector with a fused jumper. If the compressor still does not operate properly, refer to HVAC Compressor Clutch Does Not Engage diagnostic in SI.
Important: DO NOT USE A/C low pressure cycling switch, P/N 15035084 on the vehicles listed above.
If the compressor does operate correctly after tapping on the switch or jumping the low pressure cycling switch connector, replace the low pressure cycling switch (2), P/N 89040362. Refer to Air Conditioning (A/C) Low Pressure Switch Replacement in SI.
Perform the Air Conditioning (A/C) System Performance Test in SI.
Disconnect the J 43600 ACR 2000 Air Conditioning Service Center.
Remove the fender covers and close the hood.
Thanks D Dog, I'll look into it.
