# '04 GMC 2500HD AC Issue



## markq (Sep 22, 2005)

Hey guys.....the AC in my truck is not blowing cool anymore. I only have about 39K miles on the truck so I'm thinking there must be a leak in the cooling system somewhere. I called a couple places and was told that it will cost $99 (plus freon I think) just to flush and re-pressurize the system, then they'll be able to search for the leak. Once they find the leak then I'll have to pay to get that fixed, and i'm assuming another $99 to re-pressurize the system.

Does this sound right to you?!? I usually do as much of my own mechanic work as I can, but I don't know much at all about the AC systems.

I bought one of the recharge kits from Walmart, but it dint seem to work correctly, or at least I couldn't get it to. Its supposed to have a red color to it so you can see if its leaking, but I couldn't even get the pressure system to work the way the package said it would.

With temps hitting 100 + its unbearable driving around in that thing.

Anyone had issues with their AC, or have any advice for me?

Thanks!!!


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## PLM-1 (Nov 29, 2004)

markq said:


> Hey guys.....the AC in my truck is not blowing cool anymore. I only have about 39K miles on the truck so I'm thinking there must be a leak in the cooling system somewhere. I called a couple places and was told that it will cost $99 (plus freon I think) just to flush and re-pressurize the system, then they'll be able to search for the leak. Once they find the leak then I'll have to pay to get that fixed, and i'm assuming another $99 to re-pressurize the system.
> 
> Does this sound right to you?!? I usually do as much of my own mechanic work as I can, but I don't know much at all about the AC systems.
> 
> ...


There is a TSB out on this. Let me dig it up.


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## PLM-1 (Nov 29, 2004)

Subjectoor A/C Performance - A/C Will Not Blow Cold Enough (Perform A/C System Checks, Replace Accumulator, If Necessary) #02-01-38-007C - (07/27/2004)

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

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).
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&pubid=271#ss1-1539443">Condition

Some customers may comment on less than desirable A/C performance, especially when the ambient temperature is above 32°C (90°F).
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&pubid=271#ss2-1539443">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.
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&pubid=271#ss3-1539443">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).
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&pubid=271#ss4-1539443">Parts Information

Part Number
Description
89018601
Accumulator
15136596
Hose Assembly
15136597
Bracket
10372792
Insulator
Parts are currently available from GMSPO.
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1539443&pubid=271#ss5-1539443">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
*This a unique Labor Operation Number for use only with this bulletin. This number will not be published in the Labor Time Guide.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

© Copyright General Motors Corporation. All Rights Reserved.


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## markq (Sep 22, 2005)

*..............*

thanks for the info........

the top portion of the TSB says that it applies to the 6.6 Diesel. I have the 6.0 Gas.......any chance this could be the culprit on mine?

Also, will a dealership perform the work for free since there is a TSB issued, or will I have to purchase all the parts and pay the labor to get it done?

Thanks for the help!!!


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## jce4isu (Sep 12, 2005)

my 05 2500hd did the same thing change the filters in the truck pass side i bet that will help


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## PLM-1 (Nov 29, 2004)

markq said:


> thanks for the info........
> 
> the top portion of the TSB says that it applies to the 6.6 Diesel. I have the 6.0 Gas.......any chance this could be the culprit on mine?
> 
> ...


Unfortunately, I do not believe that TSBs are covered in any way, which is BS IMO. I'm not sure if it applies to the gas engines or not. Look on your compressor and see if it says DENSO on it or not. I'm curious


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## PLM-1 (Nov 29, 2004)

jce4isu said:


> my 05 2500hd did the same thing change the filters in the truck pass side i bet that will help


There are no cab filters on the 03 or newer trucks ... only the 00-02.


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## markq (Sep 22, 2005)

*........*

Thanks for the info PLM

I'll check the compressor this weekend if I get a chance.....

So will I need a new compressor? The TSB referred to the accumulator, hose and bracket.

I there a way that I can SAFELY depressurize the system and replace the parts myself, then just have it charged back up?

I don't know much at all about the AC systems - can I depressurize it, do I need special tools, etc?


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## PLM-1 (Nov 29, 2004)

markq said:


> Thanks for the info PLM
> 
> I'll check the compressor this weekend if I get a chance.....
> 
> ...


No I don't believe you will need a new compressor, the accumulator and lines are "supposed" to correct the malfunction. I know in my state, you can recharge R134a systems yourself. You can buy the kit at Oreillys, Autozone, etc


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## 75gmck25 (Feb 22, 2003)

I've done quite a bit of work with the A/C on my '75 GMC and its difficult to recharge it correctly without the right equipment. Depressurizing is fairly simple (like letting air out of a tire), although in most states you are supposed to recover R134, not release it into the air.

Once you find and repair the leak, or replace the accumulator (including PAG oil), you will have a system with very little R134. You will also have air and moisture in the system. 

To recharge it properly you first need to have a vacuum pump that will draw about 29-30" of vacuum on the A/C system, and maintain that draw for at least 30 minutes. That will pull out all the air and moisture. Then shut off the machine, and wait about 10-15 minutes to make sure your system will hold vacuum - this is your first leak check. Then use an A/C machine to recharge the system with a measured amount of R134a, or use a manual hose set and cans of R134a to charge the system. Its also a good idea to add some leak detecting flourescent dye to the system. Then, with the A/C operating, use an R134a electronic leak detector to check for leaks. Also turn off the lights and use a black light to check for evidence of leaks that show the flourescent dye. If you don't find any leaks and the system has the right charge, you should have good cooling.

Bruce


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## markq (Sep 22, 2005)

*.......*

so it sounds like I can replace it myself, but then will have to take the truck into the shop to have it tested and re-pressurized.

Any idea how much the parts will run, and how difficult is it exactly to replace the accumulator and hose?

Thanks for all the info!!


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## 75gmck25 (Feb 22, 2003)

I don't know your model of truck, so disassembly will vary. Some trucks have standard fittings where you can use an open end wrench on each side and just unscrew them. Other newer trucks have brand-specfic snap apart fittings that require a special tool to pop them apart. However, I don't think the special tools are that expensive.

Accumulators are usually about $30-40, but they might be more for a newer vehicle. Hoses vary quite a bit in price, and sometimes its cheaper to have the A/C shop make a replacement hose.

You will also need some nylog lubricant and new green O-rings for the reassembly of any fttings you disconnect, but that won't cost very much.

You might want to try looking through the user forums on www.ackits.com, and maybe even posting your questions there.

Most shops have a starndard price for a recharge and leak check, and then add on the cost of the R134.

Bruce


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