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From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Water Temp Gauge Scale Readings
OK, I have always been under the impression that the third thick mark on the 82 gauge was 195* which would be a normal reading when the motor was running at temp in a normal perfect world. However, I'm not so sure now. I can not find any real info on the face scale of the gauge that says what the white hash marks really mean in the way of actual temp. All I can find is an OHM reading which does me no good at this point, really. Can someone with the correct info inform me what the hash marks indicated by red arrows in the pic are supposed to be in the way of a temp or maybe an article on this? I think Wilcox has OHM readings. Thanks.
Sorry about the quality of the pic, my car was covered in the garage and it was dark. I know, I was being lazy.
The scale markers on your gauge would appear to be 100F, 150F, 200F, 220F with red zone starting at 240F. GM 'normally' intended their analog gauges to be at "expected" position with the needle pointing vertically (straight up). With your temp gauge, that would mean a reading of 220F would be in the range of "normal". And, with a 195F thermostat, your car on hot day with A/C on and driving at low speeds could be at 220F easily.
I don't know if that helps, but you should also know that GM never intended for those gauges to be ACCURATE; their only intend was that they be 'in the ballpark' and REPEATABLE. If you see the gauge needle in the same position as it has always been, you are 'good to go'; if it is significantly lower or higher than what you normally see, there is a problem and you should investigate. Using a GM temp gauge to assess accurate temp readings is very questionable.
Can an infrared temperature reader. They even have them at Walmart now. And you can get an idea what your engine temperature is at any given gauge reading. Looking at Wilcox is picture, 800 ohms to 7 ohms. That resistance swing is not something that can be dialed in to a precise reading.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
OK, thanks for the clarification on the numbers, which I thought I was close, but my IR gun and gauge now don't match up for some reason and trying to figure out if it's the gauge or something else. I still have the same readings with a new NOS sender as the old one which has worked fine for the last 26 years. What I wanted to do was "cal" the gauge to a little more accurate reading with the adjustable resistor, not because I would use it as a gospel reading, but rather to just give me a better idea when things are not right vs. a gross reading from stock GM gauge. Call it a more warm fuzzy if you will. Right now my gun is telling me that the motor is running at 180-185 with a 180 stat which is fine, but the gauge is reading 200 randomly and even saw it go higher and beg out hot and come back down a couple seconds later. While driving, that is not a good feeling and makes me wonder. I would hate to prang a new motor with 500 miles before I even get to go to the track with it this winter to see what it will do now that the temps are great for racing in AZ.
Last edited by Buccaneer; Oct 11, 2018 at 02:42 PM.
OK, thanks for the clarification on the numbers, which I thought I was close, but my IR gun and gauge now don't match up for some reason and trying to figure out if it's the gauge or something else. I still have the same readings with a new NOS sender as the old one which has worked fine for the last 26 years. What I wanted to do was "cal" the gauge to a little more accurate reading with the adjustable resistor, not because I would use it as a gospel reading, but rather to just give me a better idea when things are not right vs. a gross reading from stock GM gauge. Call it a more warm fuzzy if you will. Right now my gun is telling me that the motor is running at 180-185 with a 180 stat which is fine, but the gauge is reading 200 randomly and even saw it go higher and beg out hot and come back down a couple seconds later. While driving, that is not a good feeling and makes me wonder. I would hate to prang a new motor with 500 miles before I even get to go to the track with it this winter to see what it will do now that the temps are great for racing in AZ.
If you want to calibrate the gauge, then purchase the adjustable resistor I make... The resistor allows you to make a linear change to a non linear gauge.
You only need to 'calibrate' your gauge at the 200*F point. That is in the near vicinity of where a normal engine will run and just below the boiling point of unpressurized water. If you know that the gauge is close to being right at that temp, a bit either way can't be too far off. Whether it is accurate at 100*F or at 250*F is irrelevant.
Also, you should recognize that the T-stat does not [normally] regulate stabilized temperatures of the engine. It only establishes the MINIMUM temp of the engine. The capability of the radiator and cooling system will determine the final stabilized temperatures, and unless your system has EXCESS cooling capacity, it will nearly always stabilize somewhere higher than the T-stat's rated temp. Also, the engine's temp sensor is installed in one of the cylinder heads and will measure water temps IN THE HEAD. Your IR unit will look at radiator tank, hose inlet housing, etc and will be a significantly different temperature. The cylinder head location is likely the 'worst-case' point in the engine having the highest coolant temps; everywhere else will be lower (usually).
Again, the purpose of the coolant temp gauge in your car is so that you can detect a CHANGE in normal engine behavior and then DO SOMETHING about it.
OK, thanks for the clarification on the numbers, which I thought I was close, but my IR gun and gauge now don't match up for some reason and trying to figure out if it's the gauge or something else. I still have the same readings with a new NOS sender as the old one which has worked fine for the last 26 years. What I wanted to do was "cal" the gauge to a little more accurate reading with the adjustable resistor, not because I would use it as a gospel reading, but rather to just give me a better idea when things are not right vs. a gross reading from stock GM gauge. Call it a more warm fuzzy if you will. Right now my gun is telling me that the motor is running at 180-185 with a 180 stat which is fine, but the gauge is reading 200 randomly and even saw it go higher and beg out hot and come back down a couple seconds later. While driving, that is not a good feeling and makes me wonder. I would hate to prang a new motor with 500 miles before I even get to go to the track with it this winter to see what it will do now that the temps are great for racing in AZ.
Don't forget that an automotive thermostat is designed to be fully open at its temperature rating. This means that it works to keep temperature UP and is incapable of keeping it down. If a cooling system is designed to keep coolant around 200F during normal operation installing a 180F thermostat will do NOTHING to reduce the operating temperature because it was already wide open at 180F!!! This is also why factory temperature gauges normally have non-linear scales. The thermostat maintains a minimum temperature (usually top dead center on the gauge) but it takes a fairly substantial increase in temperature (beyond "typical") for it to move past top dead center.
IR temperature guns are certainly handy but unless they have an emissivity adjustment (and you know how to use it based on the surface temperature of the FINAL surface of what you are measuring) they can give wildly incorrect measurements
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Thanks, I completely understand how a T-stat works, what it's for, what it does and why. That is not the issue. My motor runs rather cool like I said at about 180-185ish almost all the time. I think there is something wrong with the gauge since it will sometimes go past 200* for no apparent reason and higher. It has several times gone from a normal reading to 260* pegged for no reason, sit there for10-20 seconds and then slowly come back down to its 180-185 range and be fine. I did check everything, one time with the IR gun when it did that 260* stunt by pulling over, but everything on the motor was well within temp normal ranges. At that point after checking the harness I assumed the temp sensor was wigging out and replaced it with a GM NOS sensor and with the same results so I'm also now assuming that it's now the gauge. It may be just coincidental that this all happened after the new motor change, I don't know since it has never done this before with other motor changes over the 26 years I've owned the car. I guess I'll figure it out, it's just a PITA right now since I want to race this winter which is very soon and I just don't trust it right now.
GM temperature senders and for that matter all others on the C3 and older cars have not been accurate since GM sent production to Mexico.... This happened around 1992, and they've been screwed up ever since. Using a NOS sender manufactured after 1992 or one of the newer ones from GM A/C Delco is not going to make your dash unit work correctly.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Originally Posted by Willcox Corvette
GM temperature senders and for that matter all others on the C3 and older cars have not been accurate since GM sent production to Mexico.... This happened around 1992, and they've been screwed up ever since. Using a NOS sender manufactured after 1992 or one of the newer ones from GM A/C Delco is not going to make your dash unit work correctly.
Willcox
Good point, but I don't know where to find a good one then that will work even close. My old one, probably from 82 worked just fine for the 26 years I've owned the car, but the one seems to be the same as the old one that is why I think it is the gauge, I may be wrong though. Thank you for your input any suggestions on a temp sensor that you works even somewhat correctly? Part number, brand etc...?
Good point, but I don't know where to find a good one then that will work even close. My old one, probably from 82 worked just fine for the 26 years I've owned the car, but the one seems to be the same as the old one that is why I think it is the gauge, I may be wrong though. Thank you for your input any suggestions on a temp sensor that you works even somewhat correctly? Part number, brand etc...?
Good point, but I don't know where to find a good one then that will work even close. My old one, probably from 82 worked just fine for the 26 years I've owned the car, but the one seems to be the same as the old one that is why I think it is the gauge, I may be wrong though. Thank you for your input any suggestions on a temp sensor that you works even somewhat correctly? Part number, brand etc...?
This is exactly why I made the adjustable resistor.... About 10 years ago someone purchased a TU5 from us and swore it read correctly... it was a fluke. There are only a few manufacturers of the senders in the aftermarket field, LL makes one, American Corvette inports another one, then you have Wells, Standard, Borg and so on....
I've tested every one of them over the years and none of them were within the proper guide lines. Heck the TU-5 which is made by wells (auto zone) wouldn't even get below 105 ohms in testing at boiling point. So basically when the sender topped out at 105 the car could get hotter and you'd not even know it. You can see from the picture above that it takes 85 to reach 220 on the gauge and with the TU5 it was impossible.
You can try another sender, and if you don't get a one that works there is a solution.
Willcox
Last edited by Willcox Corvette; Oct 14, 2018 at 12:31 PM.
I highly recommend the Willcox adjustable resistor. It is fantastic. I should have ordered it when I first saw it, and instead I put it off and went off swapping senders and doing goofball experiments. When I finally put this in my gauge read correctly for the first time in years!
I highly recommend the Willcox adjustable resistor. It is fantastic. I should have ordered it when I first saw it, and instead I put it off and went off swapping senders and doing goofball experiments. When I finally put this in my gauge read correctly for the first time in years!
The adjustable resistor gizmo from Willcox is a great item.... IFthe sender you have actually works and provides relatively smooth resistance changes from 140F-250F. The sender must be at least functional for it to allow calibration. Checking that out is pretty simple if you have an ohmmeter, a cooking stove, and a food temp thermometer. Remove the sender from the vehicle; connect a wire lead to the sender output terminal and one to the metal body of the sender; connect those leads to an ohmmeter set to the 1K-ohm range; stick the sender in a pot of cool water and stick the thermometer in with it. Now turn the heat up to it...on medium so it will get to boiling, but not too quickly.
As the thermometer reaches specific settings, record the associated ohms from the ohmmeter: 100F, 150F, 180F, 200F, 212F (boiling). If you put some salt in the water, you can get it to boil at a higher temperature (maybe 220F). You can compare that info with the stat data Willcox provides.
Last edited by 7T1vette; Oct 14, 2018 at 08:31 PM.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Originally Posted by 7T1vette
The adjustable resistor gizmo from Willcox is a great item.... IFthe sender you have actually works and provides relatively smooth resistance changes from 140F-250F. The sender must be at least functional for it to allow calibration. Checking that out is pretty simple if you have an ohmmeter, a cooking stove, and a food temp thermometer. Remove the sender from the vehicle; connect a wire lead to the sender output terminal and one to the metal body of the sender; connect those leads to an ohmmeter set to the 1K-ohm range; stick the sender in a pot of cool water and stick the thermometer in with it. Now turn the heat up to it...on medium so it will get to boiling, but not too quickly.
As the thermometer reaches specific settings, record the associated ohms from the ohmmeter: 100F, 150F, 180F, 200F, 212F (boiling). If you put some salt in the water, you can get it to boil at a higher temperature (maybe 220F). You can compare that info with the stat data Willcox provides.
I was going to try this with my original one to see how it reads and then the new NOS sensor and see how that one reads and compares. Here is a simple pic for my benefit I put together or for anyone who wants this info...Enjoy!
Last edited by Buccaneer; Oct 14, 2018 at 11:54 PM.
Water Temp Gauge Scale Readings
Right now my gun is telling me that the motor is running at 180-185 with a 180 stat which is fine, but the gauge is reading 200 randomly and even saw it go higher and beg out hot and come back down a couple seconds later. While driving, that is not a good feeling and makes me wonder. I would hate to prang a new motor with 500 miles before I even get to go to the track with it this winter to see what it will do now that the temps are great for racing in AZ.
That was my plan in the end for sure. I just need to verify that my gauge is either good or bad first, that's the issue right now. Thanks
