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James, Ford Technician
Category: Ford
Satisfied Customers: 3628
Experience:  Ford Senior Master Tech, Ford gas and diesel expert, ASE Certified
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I have an 08 Ford Focus. The engine light is on. I had it

Customer Question

I have an 08 Ford Focus. The engine light is on. I had it put on the thing at Auto Zone and it said its one of 3 things. Low coolant, thermostat bad or a sensor for temp. Coolant level is good. Car is not overheating. What it does is when it warms up the gauge goes to normal temp. But when I turn on heat or defrost the temp gauge drops to below cold. It still has heat but not as good as when before temp drops on gauge
Submitted: 1 year ago.
Category: Ford
Expert:  James replied 1 year ago.

Hello, It sounds like your thermostat is opening to soon. This happens a lot on Ford where the engine is operating at 170 degrees instead of 190. This is enough to set a code or codes for thermostat or incorrect engine temperature.

Customer: replied 1 year ago.
I need to change thermostat not a sensor?
Expert:  James replied 1 year ago.

It's rare the temp sensors go out. 99% of the time it's the thermostat.

Customer: replied 1 year ago.
It just seems like if it was a stuck thermostat it wouldn't warm up at all, and only drops down when I use the heat.
Expert:  James replied 1 year ago.

Thermostats can fail in different ways. They can stick closed and cause the vehicle to over heat. They can stick open so the vehicle won't warm up. Newer vehicle the spring weakens and the thermostat open soon than it should. When this happens you can still have heat but doesn't mean the vehicle is operating at optimal temperature. That is why a code sets because it can affect engine performance.

Expert:  James replied 1 year ago.

Hello, am I still able to offer you assistance.