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Old 08-09-2020, 09:15 PM   #1
drolston
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Default Temp Gauge Adjustment

My temp gauge is reading too high to live with. Placing 1.5 volt D cell on the power input to the gauge, with the wire to sender grounded, moves the needle from barely visible right to the 3/4 mark. Bought a replacement on Ebay which exhibits the exact same response. Okay, it was the cheap one; supposedly NOS but clearly well used. So, it is entirely possible that I have two bad gauges. I opened up the cheapo unit and noticed that the thin insulation around the very thin heater wire was deteriorated. Also found that the adjustment teeth can move the needle power-off point, but can not fully correct my too-low deflection problem.

So, before I buy the expensive replacement gauge, please confirm (JSEERY?) that 1.5 volts should put the needle on a correctly functioning Temp gauge near the center mark.
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Old 08-09-2020, 09:50 PM   #2
JSeery
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Default Re: Temp Gauge Adjustment

The 1.5v battery (D Cell) is a modern test that mimics the suggest Ford test. Fords is a little more elaborate but the same concept. Ford test uses a voltmeter across the gauge and a variable resistor. You adjust the variable resistor (which is connected to power) until you get a reading of 1.5 volts. Then check that the guage is showing mid-scale. So, the short answer is, yes, with 1.5 volts the gauge should read mid-scale.
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Old 08-09-2020, 10:00 PM   #3
19Fordy
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Default Re: Temp Gauge Adjustment

Are you sure you have the correct temp. sender unit for the engine.
I know later 1950's engine had temp. sending units of various calibrations.
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Old 08-09-2020, 10:09 PM   #4
drolston
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Default Re: Temp Gauge Adjustment

Quote:
Originally Posted by 19Fordy View Post
Are you sure you have the correct temp. sender unit for the engine.
I know later 1950's engine had temp. sending units of various calibrations.
The third 37-53 reproduction sender was working okay until a few months ago. I may have inadvertently shorted the sender wire to ground for long enough to damage the gauge. As much as I hate working under the dash, I should be more careful!
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Old 08-09-2020, 10:14 PM   #5
JSeery
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Default Re: Temp Gauge Adjustment

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Originally Posted by drolston View Post
The third 37-53 reproduction sender was working okay until a few months ago. I may have inadvertently shorted the sender wire to ground for long enough to damage the gauge. As much as I hate working under the dash, I should be more careful!
Wouldn't think that would damage the gauge, the sender is basically a controlled short to ground. But I don't really know if putting 6-7 volts through the gauge would damage it or not. There are several folks that claim they run 12 volts through the gauges on a conversion without a voltage reducer with no ill effects. Not something I would do.

Back to Ford, they do say: CAUTION: Be sure the full resistance is in the circuit before connecting the leads to the gauge unit to prevent any possibility of applying too much voltage to the gauge.

So, looks like Ford believed you could damage the gauges with direct voltage being applied to them. Never understood )or believed for that matter), the 12v on the gauges without damage, but that is through the sensor resistance.

Last edited by JSeery; 08-09-2020 at 10:21 PM.
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