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Has anyone heard of using a resistor in the circuit to correct the tendency of these older cars to have incorrect higher than actual coolant temperature readings? I think the theory being the newer sending units are not compatible with the guage.
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Re: C1/C2 Coolant Temp Guage Readings
Bill: Check out an article I wrote in the Restorer in the early 90s about tempature sending units. The newer replacements were not calibrated properly. Someone wrote a later article suggesting adding resistance. I found that for many sending units you needed approximately 30 ohms to get a proper reading at 180 degrees. The problem is if you add 30 ohms your guage may never indicate you have reached 220 degrees. You thus run the risk of not knowing you actually overheated. You might add 10 or 20 ohms and play it safe, but I would recommend you find one that is calibrated properly. I found that 1975 Buick small block sending units from Advance Auto in Va. looked much like the correct one and 30% of them were properly calibrated. I took an ohm meter to the parts counter and measured them at room temperature. You should get at least 600 ohms. 700 ohms at 70 degree room temp should indicate you have a good temp sending guage. Dwight Farmer -
Re: C1/C2 Coolant Temp Guage Readings
Bill: Check out an article I wrote in the Restorer in the early 90s about tempature sending units. The newer replacements were not calibrated properly. Someone wrote a later article suggesting adding resistance. I found that for many sending units you needed approximately 30 ohms to get a proper reading at 180 degrees. The problem is if you add 30 ohms your guage may never indicate you have reached 220 degrees. You thus run the risk of not knowing you actually overheated. You might add 10 or 20 ohms and play it safe, but I would recommend you find one that is calibrated properly. I found that 1975 Buick small block sending units from Advance Auto in Va. looked much like the correct one and 30% of them were properly calibrated. I took an ohm meter to the parts counter and measured them at room temperature. You should get at least 600 ohms. 700 ohms at 70 degree room temp should indicate you have a good temp sending guage. Dwight FarmerComment
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