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If you had to add coolant you have a leak in the coolant system. You need to go to Autozone you rent the coolant pressure tester. You need to do this test with the engine cool, and it must be full of coolant. You will then pump air into the system and listen and look for noise and leakage. A coolant leak can be hard to find, if the gauge goes down you have a leak. Check the ground if there is a puddle then try to determine where it is coming from, look at the hoses, intake gasket,radiator, freeze plugs. You can rent the tool for free at Autozone, you just give them a deposit to use the tool and you get every dollar back when you return the tool.If you do not see a puddle check the floor board on the passager side front for wetness, if it is wet the heater core is your problem. If there is no wetness it could be a head gasket and you need to examine the oil for coolant in the oil. Then you need to do a compression test one the cylinders to confirm if it is the head gasket.
When the coolant gets low in the vehicle the heater will not work. the coolant needs to be at a certain level for it to work.
Now if the coolant is full and the engine fan is running it could be a bad fan relay, you can switch the relay with another relay in the junction box next to the battery. Remove the lid and flip it upside down to see the diagram of the location of the fan relay. It could be a bad ground in the relay not telling the fan to turn off. You can switch the relay with another one that has the same part number. Like the Horn
Now if the coolant is to low the temputure sensor will trigger the fan to come on do to lack of coolant to keep the engine cool. Keep check the coolant level.
Ok so you need to find the leak, then switch the relay for the fan around with the horn and see if it works correct.
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