2000 yukon denail front a/c not cold rear a/c is

Check your low pressure line feeding your evaporater coil, if its not getting cold mreplace your orfice

First of all get the Freon level checked, if Freon/ refrigerant is low then it can cause this problem.Wen Freon is low it takes time to cool.--- So first get Ac pressure tested.It can be tested at any local car garage.Some times pressure will be checked OK, but still if Freon is getting clogged in the line/ tube then it will not reach the front , but reaches rear then front will not cool, but rear will.--------

But mostly this problem is related to blend door.

If the rear is working well and front is not I would suspect a blend door or actuator issue in the front.Double check and see if you can hear anything moving when you are adjusting temperature from hot to cold.Also check and make sure the air flow moves properly from defrost to vents and floor etc.

Either a bad blend door motor or Climate Control Assembly. The A/C heater function selector switch combines a vacuum selector valve for direct control of the vacuum control motors and electrical input to the instrument cluster module.

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The blend door actuator is located behind the glove box.-----

To see blend door diagram for your Yukon Denail, click the link below :---

http://howtobyme.blogspot.com/2011/08/where-is-blend-door-actuator-located-on.html

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This will help.Thanks.Helpmech.