When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello. Question on Temp Sending unit OHMS as it relates to temperature read out on Dash Gage. I have a 1982 if it makes a difference in the C3. I have searched the web for a chart on what OHM output of sending unit correlates to the temp gage. I have found conflicting info. I have found 90 Ohms and 78 Ohms should be about 200F. And as I understand it, the colder the engine the higher the resistance, the hotter the engine, the less resistance. I purchased the O'reilly 28335 sender and tested it along side one that I was running in the car. The one I was running in the car hit 240F on the gage when it was around 160F @ the Thermostat housing by IR Gun). Even more confusing is that both of them read 175's OHMS as the water boiled, indicating to me that that the gage should be way below 210, if what I found on the web is correct (78-90Ohms @ 200). I am confused as ever. I just want the gage to be somewhat accurate to what the engine is doing so I can tell if I am actually starting to get hot. Any guidance would be appreciated.
Last edited by markkrollc3; Dec 16, 2024 at 09:21 AM.
See the video above for the adjustable resistor. Hopefully you have your original temp sender.
On my 68 my gauge had read low for decades. I then bought the adjustable resistor from Willcox and dialed it in. It works wonderfully. Not sure where you can find one of these nowadays..... but it is wonderful.
Here is my story on that: https://www.corvetteforum.com/forums...-question.html
Hello. It is the Water Temperature in the driver side head. So it sounds like the only solution is to get a variable resistor and dial the temp gage into an IR gun reading. Is this what I am hearing? Where should I take temp? I amthinking maybe a few spots (Near sending unit, Thermostat housing and maybe somewhere on passenger head) and average them. Then dial resistor until the gage reads that average......
I cannot seem to find the Willcox type adjustable resistor that replaced the original anywhere. Ecklers has a picture but not the part. Anyway, just take the temp that the thermostat outlet with the IR gun. that way you won't get misleading info from the exhaust manifolds. Maybe you can call them? I added the link and pic from their website below
Hello. It is the Water Temperature in the driver side head. So it sounds like the only solution is to get a variable resistor and dial the temp gage into an IR gun reading. Is this what I am hearing? Where should I take temp? I amthinking maybe a few spots (Near sending unit, Thermostat housing and maybe somewhere on passenger head) and average them. Then dial resistor until the gage reads that average......
More info from the C2 world. And, yes, it the Willcox unit is fairly accurate throughout the range since it does not JUST adjust for one single normal operating temperature value....but you need to have the appropriate temp sensor (like the original - see my testing text in post #3)
Lotsa info here: https://www.corvetteforum.com/forums...-resistor.html
Last edited by carriljc; Dec 17, 2024 at 11:17 AM.
I had issues with my coolant temperature sender and ultimately found that I had a bad sender. I was able to get an ACDelco (#213-4793) and it has been very accurate.
The more and more I dug into information about the resistor method the more and more I determined it was not an accurate approach. There are some steps you can take to verify the gauge in the dash is working right but I can't remember off the top of my head where I found it. If I recall correctly, you should be able to ground the wire that goes to the sensor and if you turn the key to the on position (not starting the engine) it should "peg hot". I swapped out my sensor in August and it's been highly accurate since.
C3 1982 Temp Sending Unit Question
