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Q: my temperature gauge rises slowly when its in drive and idle. once i start driving, it quickly drops. what could be the issue?

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When i start my car waiting for it to warm up everything is fine. About 5min into my drive my temperature gauge rises when i am stopped on the street for long periods. Once i drive off the gauge immediately drops to operating temperatures. My heat runs warm turned up. And a good portion of coolant from my radiator fills my reserve tank from between L and F to Full
My car has an automatic transmission.

Hi there. From the description you have provided, this could be an inoperative radiator cooling fan issue. Turning on the a/c, this should turn the radiator cooling fan(s) on, which would help identify whether the cooling fan(s) are capable of turning on. If, the fan(s) turn on, then it could be a faulty coolant temperature fan switch. If, the radiator cooling fan(s) don’t come on with the a/c on, it could be, a blown radiator cooling fan fuse. It could be, a faulty radiator cooling fan relay. It could be, a faulty radiator cooling fan motor. I recommend having your vehicle’s temperature gauge be diagnosed and repaired by a certified technician, such as one from YourMechanic.

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