How to Troubleshoot a 1999 Yukon Air Conditionerby Joshua Bailey
The 1999 GMC Yukon came with a large, 5.7-liter V-8 engine that pushes out more than 255 horsepower. Generally, large V-8 engines give off a lot of heat. That heat eventually leaves the engine compartment and enters the cockpit through the air vents. This means you need to have a high-powered air conditioning system to cool everyone down during the summer months. If the air conditioning unit is not responding as it should, it is easy to diagnose the problem.
Turn the Yukon on and turn the air conditioning unit on. If the compressor works, move on to Step 2. If the compressor does not turn on, it will need to be replaced. This is a repair that should be handled by a professional technician.
Connect the Yukon service fitting nozzle to the recharge air can and attach the hose to the end of the nozzle. Twist the nozzle's top to release a small amount of air and close it after a second. This will clear the hose of any extra air.
Open the Yukon's hood and turn the Yukon on. Put the air conditioning on "High" or "Max." Connect the recharge hose to the Yukon's air conditioning valve. The valve is found on the rear wall of the engine compartment. The valve cap will be blue. Open the service valve on the recharge can to shoot the recharge vapor into the Yukon's air conditioning unit. Stop when the hose gauge reads between 25 and 40 psi.
Allow the air conditioning to run on high for five minutes. This will test whether there is a leak. If the air stays cool for the entire time while the air conditioning unit is running, you more than likely just ran out of coolant.
Monitor the air conditioning on the 1999 Yukon for the next few months. If the air conditioning unit stops releasing cold air after only a few weeks or months of use, there is a leak. This means you will have to get the unit flushed or replaced.