Q: Heater was not blowing warm air and then the engine overheated.

asked by on December 10, 2016

I was driving at about 65mph when I noticed my heater was not blowing any warm air. I then looked at my temp gauge and saw it was almost to the red so I pulled over and shut the engine off. I got a ride back into town and picked up anti-freeze which I added upon my return. I started my vehicle and started home. The temp was normal until i engaged the heater. The temp started climbing but dropped when I turned the heater off. I tried the defroster which worked fine and did not cause a temp spike. I stopped at a part store to get advice on the issue but it was already closed. I got back in my vehicle, started it and continued home only now the defroster was not working. I arrived home and turned the heater on again to see if it spiked again and it did not and now I can't feel any air cold or warm coming from the vents. The vehicle has always been driven in Texas bit now work has me in North Dakota which is a big change and probably what is causing issues but how can I fix my car? Thanks

My car has 135000 miles.
My car has an automatic transmission.

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The heater not working in some cases may be related to the overheating problem you are also having. This may be due to a faulty heater blower motor or potentially a bad heater core. As you may know, the heater core is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. When the cooling system is not properly circulating coolant through the motor, this results in the warm coolant not being pumped through the heater core properly in order to warm the inside of the vehicle.

Engine overheating can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning on and off at specific temperature thresholds. When this switch is not working properly, this can cause the fans to come on intermittently, all the time or sometimes not at all. When this happens you will notice a temperature spike and drop occasionally as the fan comes on and off. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. As mentioned above, this also restricts the warm coolant from flowing through the heater core which uses this to blow warm air into the cab of the vehicle. I would suggest having an expert from Your Mechanic come to your home to diagnose your cooling system.

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