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06-07-2020, 10:32 AM | #1 |
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valid Temp Sending unit test?
I have tested all the gauges in the 1952 Crestline using the variable resistance method in the Shop manual. In essence using a resistor instead of the actual sending unit. Adjust the 50 ohm resistor until a reading of 1.5 volts is measured between the Volt input and the sending unit terminal should give a gauge reading of near the center of pointer travel. It does on Gas, Oil and Temp gauges. I connected the actual temp sender to the gauge and suspending it in a can of water that I heated to boiling. The gauge with no voltage sits at the high end of the range. as soon as the voltage is turned on to 12V with a Runtz regulator and the water room temperature the gauge drops to a couple pointer of widths below highest reading. As the water is heated up, the gauge steadily drops to max cold reading. Obviously the opposite of what I would expect a good setup to do. see in flaws to my test setup? I was thinking of buying an aftermarket sender unit. My thought was to use the dash gauge for one side of the engine and a mechanical gauge for the other. What readings should I expect with a good sending unit? Where does the gauge sit at startup and does it increase proportionately at the engine temp increases and where on the gauge is normal operation temperature. I get the impression that there is little difference between normal operation temp and boiling on the gauge. Thanks
Last edited by Scott52; 06-07-2020 at 10:34 AM. Reason: add photo |
06-07-2020, 10:44 AM | #2 |
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Re: valid Temp Sending unit test?
Is that sender correct ??
From what i see it looks different from what i´m used to... A sender can go from low to high or other way around...usually from low to high on temp since a broken wire will indicate hot and get drivers attention. Wrong type sender and it will work as you state. |
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06-07-2020, 10:47 AM | #3 |
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Re: valid Temp Sending unit test?
Are there any "shorts" in your test circuit the way it's hooked up?
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06-07-2020, 03:50 PM | #4 |
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Re: valid Temp Sending unit test?
No Shorts. Here is the sending unit that came from the head that had already been removed from the engine when I bought the car.
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06-07-2020, 05:21 PM | #5 |
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Re: valid Temp Sending unit test?
Well, it sure isn't original, so no telling what it is.
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06-07-2020, 11:17 PM | #6 |
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Re: valid Temp Sending unit test?
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06-08-2020, 12:59 AM | #7 |
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Re: valid Temp Sending unit test?
My ‘50 has a gauge setup as you describe. When the mechanical side is at 180*, the electric side is at 3/4.....if that makes sense?....I’m unable to take pick till later today......Mark
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06-08-2020, 08:00 AM | #8 |
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Re: valid Temp Sending unit test?
Flathead ford8 That is a normal reading you should see for a 6v neg ground system
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06-08-2020, 09:17 AM | #9 |
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Re: valid Temp Sending unit test?
There was a thread a while back on how to take the stock temperature sending
unit apart and repair them. |
06-08-2020, 09:30 AM | #10 |
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Re: valid Temp Sending unit test?
One idea is that the sender I have is not a Ford King Seely sender or a replacement. I don't care about super accuracy. How do the replacement, resistance type senders work with the original gauge in terms of gauge reading. I should be able find a mark on the gauge that corresponds to 180 and 212 degrees. That is close enough for a warning. I understand that the replacement, resistance senders do work the same as the original but the must have a resistance vale that approximates the King Seely operation, especially in the normal operating range. Comments?
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06-08-2020, 09:32 AM | #11 |
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Re: valid Temp Sending unit test?
I do remember reading that repair thread. If the sender I have is an original, I can try that. but not sure my skills at taking it apart and resealing are good enough. Is it an original type?
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06-08-2020, 09:36 AM | #12 |
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Re: valid Temp Sending unit test?
Your sender pictured is most likely a stewart warner and not correct for the dash instruments which are King Sealey.
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06-08-2020, 09:39 AM | #13 | |
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Re: valid Temp Sending unit test?
Quote:
The full hot would be "zero" resistance on a sensor, but I don't know what the other end of the resistance range would be for cold. Last edited by JSeery; 06-08-2020 at 10:10 AM. |
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06-08-2020, 12:06 PM | #14 |
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Re: valid Temp Sending unit test?
Here's the posting on how to take apart and repair stock temp. sending unit. Those King/Sealy folks were pretty smart. Wonder what happened to their company?
If you have a Dremel tool you could easily cut one open and then use JB weld to re assemble. Open and scroll down. Very informative. Read all of this. https://www.fordbarn.com/forum/showt...ghlight=sender |
06-08-2020, 03:07 PM | #15 |
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Re: valid Temp Sending unit test?
Here is a picture of an original Ford sensor, what Scott has is a resistance sensor with the wrong calibration for an original Ford gauge.
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06-08-2020, 03:24 PM | #16 |
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Re: valid Temp Sending unit test?
Not only has the Stewart Warners the wrong range...they are backwards compared to ford...SW are either 240-33 or if older 120-16
Ford are if you put a ohm reading reference on them...i know i know...10-70 |
06-08-2020, 06:43 PM | #17 |
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Re: valid Temp Sending unit test?
The king steely works on a pulse or on then off ,again ,both sender and receiver have a set of points and bi metal strip,one heats up and opens the other end does same,restance type will not work!lookin a old motor manual for description of how they work
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06-08-2020, 07:27 PM | #18 |
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Re: valid Temp Sending unit test?
They wont work correctly, but they will work. The resistance in the sensor will heat the coil in the gauge, it is just a different curve than the correct sensor.
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