North American Turbocoupe Organization



Calibrating a factory temp gauge?.....
Kuch Offline
Member
#1
So with all of the temp issues our cars are known for, specifically the gauge reading wrong, I seem to remember someone here or on turboford that had the resistance readings of the different temp senders. I cannot find it through the search function. So my thinking is there should be a way to add a resistor inline for the gauge to have it read more normal based on what the ohms are for a known temp sender. Maybe an adjustable pot inline. I am just thinking of ways to have our gauges read normal with normal temps. Also, these temp senders were used by Ford for many years, but I tend to see three different colors. Red, Green , or Black topped senders. What's the differences? Any ideas?
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof, T3/T4 50 trim, 255LPH, BBK AFPR, 3" DP dual 2.5", MGW shifter, K&N, Gillis valve, RR cam
1964 Ford Galaxie 500XL, 390 6V, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 3 Speed, slow and low
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Jeff K Offline
Administrator
#2
The temp gauge sender is a NTC (negative temp coefficient) sender, meaning the resistance goes down as the temp goes up. The temp vs resistance transfer function is also not linear (it is a thermistor). If I remember right, sender resistance @ room temp is around 400 ohms, and around 22 to 25 ohms at 210 deg deg F. Putting a resistor in series will make the gauge read lower at a given temp. Many of the gauge problems in these cars is not caused by the senders or gauges, but by the archaic mechanical IVR. Solid state replacement IVRs are available on Ebay, or you can build your own for $5 worth of parts.

If you want to know the actual coolant temp install a real electric or mechanical temp gauge.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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