How does the Temp Guage Work?

[SR77]

Can someone explain how the temp guage works. If the thermostat fully opens around 192 degrees and continues cycling open and closed depending on the temp of the coolant what makes them the temp guage stay at a steady point on the gauge? Why doesn't it fluctuate alittle with the temp of the coolant? The reason i am asking this is cause the guage in my truck will drop after the thermostat opens and then will remain at that same point on the guage from then on. Thanks for the help

 

[aldive]

The temp gauge is not a real gauge but is just a fancy idiot light.

 

[IAmTodd]

Originally posted by aldive
The temp gauge is not a real gauge but is just a fancy idiot light.

The temp gauge too? Whats next, you gonna say the gas gauge is too? Although it prolly is. Can't use it for much more than that

 

[travish_1]

I don't know why but my temperature gauge does fluctuate now when the thermostate opens and closes. I had a new engine and a new radiator put in and ever since it fluctuates.

 

[SR77]

Thanks for the replys. So how does the Temp guage work then? If it is just a fansy idiot light, why does my guage drop after the thermostat opens?

 

[Howard]

The temp gauge works by using a device called a thermistor. This is a temperature sensitive resistor whose value changes with temp. The tip is within the coolant of the engine block. Just before the thermostat opens the coolant temp will exceed the 192 degree temp and after the stat opens the temp will drop slightly. Hence the gauge drops too. Hope this helps explain things a bit.

 

['96explorereddiebauer]

The only idiot gauges are the amperage and the oil pressure. The other two (gas and temp) are working gauges.

 

[IAmTodd]

Originally posted by '96explorereddiebauer
The only idiot gauges are the amperage and the oil pressure. The other two (gas and temp) are working gauges.

Thats what I thought because the one on my '95 flucuates quite a bit. I'm thinking my thermostat is going, but its done that for the past 2 years and shows no signs of getting hotter, so why fix it?

 

['96explorereddiebauer]

Mine is almost pegging at the bottom of the gauge. I think my dad and I are gonna change the thermostat on Christmas Day when he actually gets a day off from work (he owns a restaurant and decided to close down for the day).

 

[SR77]

Thanks for the replys. The reason I asked how the gauge works is cause I am having a problem with my Temp Gauge only moving up about 1/4 off of Cold and I can't figure out why. I changed my thermostat and coolant and it didn't do a thing. I guess I am gonna try changing the Temp Gauge Sender next, but if that doesn't fix it i don't know what is wrong.
One last question for you guys, When the Thermostat opens at its specified Degree, does it remain open the rest of the time the vehicle is running or does it ever close again. I am trying to figure out how the cooling system keeps the vehicle at a steady temp no matter what the outside temp is. Thanks again for all the help.

 

['96explorereddiebauer]

From my understanding, the thermostat will close again when it senses the temperature is colder than the specified range then it'll open again when it gets hot.

 

[Bored_2wd]

Just changed my thermostat today, it took me 2 hours! Their are 3 bolts you need to remove. The top right and bottom center bolts take a couple minutes total. The top left one took about 1/2 hour to remove - I ended up using a 10mm open end wrench to break it free and then a 1/4 inch drive 10mm socket, swivel, and two short extensions to remove it the rest of the way. In order to get the socket on the bolt I used a screw driver straight down from the top to keep the socket lined up. I was getting about 5-10 degrees of movement in the socket, and with the multiple joints I was just barely moving the bolt at all. Finally got it out, changed it, and took the rest of the time putting that one bolt back in.
The frustrating thing is that the temp guage is still a problem, no difference. That pretty much means it's the temp sensor. I'm going to change it tomorrow.
--Bob

 

[SR77]

Thanks. Ok, so if the thermostat cycles open and closed and the coolant temp fluctuates and the temp gauge is a working gauge mentioned earlier and not just an idiot gauge, why does the temp gauge stay at one steady spot? What causes the gauge to reamain in one spot? I just don't understand why my temp gauge will move up then drop down after the thermostat opens, but then remain in one spot if it is a working gauge and the coolant temp and thermostat continue to fluctuate while the vehicle is on. Thanks again

 

[Maniak]

Keep in mind that a thermostat is not a 2 position valve.

Next time you bored, take a thermostat and put it in a pot on the stove....

As the water gets near the thermostat setting (lets assume 195F) it will start to open. At 195 (its setting) it will be fully open. Now turn off the stove and watch it close. It will close slowly as the temp drops. If I remember correctly it will be fully closed about 150-160F (been a while since I was that bored).

This means that as it opens/closes it is regulating how much water is going through which basically keeps the water temp about the same. If it was an "open/close" only valve, the temp would fluctuate more.

~Mark