One common gauge is the cold/hot gauge, also referred to as the coolant temperature gauge.
You will find the coolant temperature gauge on either the left or right side of the dash. This gauge monitors the temperature of the engine.
Transmissions usually will not shift into the final drive gear until the engine temperature has reached at least a quarter of the way of its full gauge range. Most gauges are set to run—in normal operation—about midway of the gauge. So, you’ll usually see a “C” (for cold) on the left and an “H” (for hot) on the right (or Blue for cold and Red for hot).
The gauge could be installed vertically—in that case, the ‘C’ would be on the bottom and the ‘H’ would be on the top. The needle is typically going to be in the middle of the gauge, indicating what is called, “Normal Operating Temperature.”
Interestingly, if the indicator needle indicates your engine is staying cold, that impacts your fuel mileage. The vehicle’s computer is designed to put fuel in the engine based on a certain engine temperature. When the engine is cold, it puts in more fuel because a cold engine needs more. If the thermostat is not working—a typical failure—then the computer perceives that the engine is running at a colder temperature and continues putting more fuel into the engine, increasing your gasoline usage. Because the thermostat can affect fuel mileage, it’s important that you are familiar with the temperature gauge to know what is normal. Check that gauge on a consistent basis.
Note: If you continue running the vehicle when the gauge shows the engine is hot, this will cause very expensive and critical internal engine damage. Too many times we have seen very expensive engine damage caused by someone who knew the gauge was reading hot but explained that they only drove “less than a mile” to get to an exit, home, or elsewhere. Don’t make this mistake!
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