Heater blows cold air
1991 Nissan pickup tempeture gage moves only slightly above Cool after extended idle,and drops below Cool while driving. Meanwhile the heater never rises above luke warm at the vent.
Sounds like the thermostat to me.
Stuck open therm can cause this sort of issue. Stopped up heater core can also cause it. Locate the two heater hoses under the hood going into your firewall right below the front windshield. Crank truck up and allow it to run long enough to reach operating temp. Now carefully feel these two hoses. Is one hot and the other cold or luke warm? If so possibly stopped up heater core. Is both luke warm or cold? If so possibly therm stuck open.
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