A/C doesn't work?

Glad you got it fixed. Let me know if I can help in the future.

Take care,
Joe

Do you mean the air is blowing but not as hard as it was ( do all the blower speeds work?) OR that the air is blowing OK but it's not as cold as it was?
Those are different issues. Also do you have the automatic system (set it to a temperature on a digital readout) or the blue/red manual system.

You would need to check the low and high side pressure to help determine the source of the concern. But it does sound like a low charge.

Hi there,

Thank you for the donation,

having a flat battery is no reason for the A/C system failing, so with this in mind, I would start with checking fuses if you have not already done this, post with what you find.

Mark (mhpautos)

You have two heater cores in your truck. One up front and one over the rear wheel well.

You could have clogged heater core, stuck control valve, or one/more of the blend doors are stuck.

The only way to check is to remove the HVAC unit for the rear.

You can gain access to it by removing that rear panel over the passenger side wheel well.

Welcome to 2CarPros.

Have you replaced the belt tensioner? It may not be holding enough pressure on the belt and allowing the clutch to slip.

Here are the directions for replacement:

2003 GMC Truck C 1500 Yukon 2WD V8-4.8L VIN V
Drive Belt Tensioner - Accessory
Vehicle Engine, Cooling and Exhaust Engine Drive Belts, Mounts, Brackets and Accessories Drive Belt Tensioner Service and Repair Procedures Drive Belt Tensioner - Accessory
DRIVE BELT TENSIONER - ACCESSORY
Drive Belt Tensioner Replacement - Accessory
Removal Procedure
1. Remove the accessory drive belt.

Pic 1

2. Remove the drive belt tensioner bolts.
3. Remove the drive belt tensioner

Installation Procedure

pic 2

1. Install the drive belt tensioner.
2. Install the drive belt tensioner bolts.

Notice: Refer to Fastener Notice in Service Precautions.
See: Engine, Cooling and Exhaust > Vehicle Damage Warnings > Fastener Notice

3. Tighten the drive belt tensioner bolts.
Tighten the bolts to 50 Nm (37 ft. Lbs.).

4. Install the accessory drive belt.

Let me know.

Joe

One of your actuators may not be working or it may be acontr head for the air movement. The a/c is probably leaked out Freon is why it's not working right. Try pulling the hvac fuse for 60 seconds with key on sometimes the actuators reset and you may get air blowing through again. It may also have a wiring issue esepecially if you have seen smoke from the dash on pass side. The harness is known to melt together on these.