Temperature Gage Always reading Low

overheating

#1

The needle on my Dial Temperature Gage on my 1994 F150 Truck (5.0L V8) has always read very low, since I obtained the Truck back in 1997. After driving the Truck for about an hour the Temperature Gage will come up just a small bit to about maybe 10% to 15% of its total range. There are no temperature numbers on this Dial Type Indicator Gage just Low, Normal and High. I have replaced temperature sensor on the engine but this did not change the low reading on the Temperature Gage. Thinking that the Gage is just stuck low, I had a bit of a problem 6 months ago where my Truck broke down, the Serpentine Belt came off and about 3 minutes later the Temperature Gage peg into the High region. Giving me absolute proof that this Dial Gage can peg into the high hot region. After putting on a new Serpentine Belt in the dark in the driveway of my local dry cleaner where I was broken down the reading on the Gage return back to low slowly within 45 minutes. The Thermostat is rated 195 degrees F and I have already changed the Thermostat out about two years ago, with no luck. I think the Temperature Gage should at least read somewhere in the center region around 50% in its normal range. I could drive around town without the Serpentine Belt; this would give me a higher reading but would melt the engine. I was thinking about doing an experiment, about buying a new temperature sensor, unplugging the electrical connection off the present temperature sensor and connecting it to the new sensor, externally. Then taking the tip of the new sensor and dipping it into a pot of boiling water. This should test the Gage reading at 212 degeee F with the boiling water and at least move the needle on the Temperature Gage higher. Any thoughts about getting the Temperature Gage to read higher? Will driving with a low Temperature Gage reading affect my engine or my gas mileage? Getting about 20 mpg (city). This low reading has be a mystery with me over the years.


#2

Are you sure you changed the right sending unit. How many wires were on the one you changed? I believe your truck uses two different sending units. One has 2 wires and informs the ECM of engine temperature for fuel air mixture, and one has a single wire for the temp gauge.
~Michael


#3

[b]You have to remember that gauges that came in your vehicle aren’t exactly the most precice instruments. So don’t expect them to be to accurate.

Hey! As long as the thing isn’t overheating, I wouldn’t worry about it.

Tester[/b]


#4

Either the engine is running cold or the temperature gauge is reading low.

Does the heater blow hot air in the winter? If the air is hot, the engine is OK and the gauge is wrong. If the air is barely warm, the gauge is correct and the engine isn’t running at 195 degrees.

Running cold is not good for several reasons.


#5

I’ll check this out I didn’t know about the second sending unit. I hear what you’re suggesting. Will check it out tonight.


#6

Yes, I get great warm air in the winter. Thanks. Another writer is suggesting I may have the wrong sensor.