Jeep Grand Cherokee

What would cause my 99 Grand Cherokee heater to stop switching heat vent location Turn on defrost nothing turn on floor nothing etc. blower is working fine just switching of venting direction?



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If it's a Laredo, you probably have a vaccum line that has come off or broken. Vent switching is controlled by vaccum in these models. The main vent line comes off of the driver's side of the intake manifold. These are notorious for either slipping off or breaking.