Q: Heat wasn’t working, Changed thermostat, heat won’t work, temp gauge goes to H.
Check engine light came on and code was P0128. Also noticed that temperature gauge wasn’t reaching standard operating temperature. Changed thermostats myself. After changing them, started car and took for a ride. No coolant leaking. Temperature gauge reached standard operating temp but kept climbing. Reached H and heat still wouldn’t work. Does not seem like engine is pulling coolant from reservoir.
My car has an automatic transmission.
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Hi Eric. Thanks for contacting us today. Typically when you have an issue where the vehicle is running extremely hot and the heater does not work, it’s due to an obstruction of debris inside the heater core, or coolant isn’t getting to the heater core. If the thermostat is working, then the problem might be the water pump. Sometimes having the coolant system flushed will remove the obstruction inside the heater core, but replacement is also possible. It’s probably best to have a professional mechanic complete a heater not working inspection so they can correctly identify the root source so the right repairs can be completed.
If your radiator is not pulling coolant from the reservoir, it is possible that you have a bad radiator cap. I would recommend having the radiator cap checked by a qualified professional to determine if it is functioning properly.
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