Temp gauge question

Triple Pickle

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Would you guys have any idea about what temperature say the first mark is? Halfway? Last mark?
My car is a 70 Fury. It runs around 1/3 of the way over sometimes a little more. I don’t think it’s getting too hot and I’ve had issues with other Mopars with this kind of gauge going higher than it should. In the past I’ve panicked about this on a different car only to find that when I installed an aftermarket capillary type gauge that the factory gauge was being dramatic!
What’s your take? Thanks.
 
You could use an infrared temp sensor to calibrate your gauge?
Maybe so, if I had one. I just wondered if there was an idea of what these marks represented in actual numbers other than hot enough, this is ok and, too hot!
 
Not really a reply but what the sender should show in ohms.

uage ohms.jpg
 
I always thought the 1/3rd mark represented around 180 degrees or thereabouts. With a 190 degree thermostat, I like to see the gauge a little above the first mark. Don't know if that helps you any but if not, it is time to invest in a infra red like was mentioned.
 
My '68 Fury has the "normal" range on the gauge and when running at full operating temp the needle is about 1/4" from the end of the range. I have used my infrared thermometer at the temp sensor and it reads around 190 - 195 degrees. Temp at bottom of rad is around 40 degrees cooler. This is on a hot day, with the a/c on, just coming off the road. An infrared thermometer is a great tool to have, it has many uses, on a vehicle or around the house, and they are not expensive.
 
Used to be that the first mark was 100 degrees F. The middle mark, + or -, would be 200 degrees F, maybe 210, usually. Then the top mark was usually 260 degrees F (the approx boiling point for 50-50 coolant and a 15psi pressure cap.

That means that with a 180 degree F thermostat, the needle will be a bit below the center mark and "look good". With a 195 degree F thermostat, it would be at the middle line, still looking good with lots of reserve before things get too hot.

From my observations,
CBODY67
 
Used to be that the first mark was 100 degrees F. The middle mark, + or -, would be 200 degrees F, maybe 210, usually. Then the top mark was usually 260 degrees F (the approx boiling point for 50-50 coolant and a 15psi pressure cap.

That means that with a 180 degree F thermostat, the needle will be a bit below the center mark and "look good". With a 195 degree F thermostat, it would be at the middle line, still looking good with lots of reserve before things get too hot.

From my observations,
CBODY67
That is about where my 05 300C runs. Pretty much around the center mark. My 65 Plymouth Fury runs just a bit above the first mark. My 68 Charger has some temp numbers and runs about where the thermostat wants it to. I guess they all register a little different. As long as they are consistent in my book.

100_8670.JPG
 
Thanks guys! I borrowed a infrared thermometer from a buddy and at the sensor it read 201 with the gauge a little over the first mark.That’s where it’s been running at most of the time.
It swings up halfway before the thermostat opens in the morning. And if you shut it off to run in and out somewhere it will make a run for the “H” upon restarting, but quickly goes back down. I know this is all normal I just think these gauges are what I call drama queens compared to other makes.
 
Thanks guys! I borrowed a infrared thermometer from a buddy and at the sensor it read 201 with the gauge a little over the first mark.That’s where it’s been running at most of the time.
It swings up halfway before the thermostat opens in the morning. And if you shut it off to run in and out somewhere it will make a run for the “H” upon restarting, but quickly goes back down. I know this is all normal I just think these gauges are what I call drama queens compared to other makes.

200 F is fairly normal for this time of year. Most of the old gauges were NON-linear in response. Same goes for the old sending units. Heat soaked sending units read coolant stuck around them near the top of the coolant system, so will read plenty hot until some pumping moves that stuff.
 
200 F is fairly normal for this time of year. Most of the old gauges were NON-linear in response. Same goes for the old sending units. Heat soaked sending units read coolant stuck around them near the top of the coolant system, so will read plenty hot until some pumping moves that stuff.
Non-linear in response. THAT is the correct answer! I never thought of it that way but you’re right, they weren’t meant to show precise temperature readings. Thank you!
 
Non-linear in response. THAT is the correct answer! I never thought of it that way but you’re right, they weren’t meant to show precise temperature readings. Thank you!

Sure. Ironically enough, that property comes of "linear" designed discrete components, very crude, simple, 19th century thermo-electric stuff, which, when nailed together, would consistently respond within certain limits which the old engineers, with their slide-rules, pencils, papers, martinis, cigars and Benzedrine made into decent instrumentation! Mopar engineering lit up the sky from 1955-72, and got snuffed by bean-counters and scabby-kneed politicians.
 
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