Heater problems in 2004 jeep grand cherokee
2004 jeep grand cherokee when i start it it it will not blow warm air.Soon as i start moving it blows warm air.Been happening for about a week.No smell or anything....heater core ,no smell.
Insure that your radiator, heater core and water levels are correct. and operating correctly. then check The dampers for the duct work of heating systems are controlled by vacuum. If at idle and car is at operating temp with heater on and you feel air coming out the vents but its cold and without touching any controls you start to drive and warm air starts coming out of them I would check for a vacuum leak going to the controller. As you drive faster the vacuum increases and will provide enough pressure to move the damper but at idle with the vacuum leak not enough pressure there to move it. This vacuum line will be coming from the intake thru the firewall to behind your heater controls. . Have to have heat in the heater core first.
Only thing I can add to that excellent answer is I think water pump failing, the impellers, if plastic, can wear, albeit a 2004 might be a little soon for that, and when you increase the rps of the engine while driving, the pump spins faster and coolant flows better through engine and heater core. However dandy's post is more likely.
Only blowing cool air
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