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Old 06-07-2020, 10:32 AM   #1
Scott52
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Default 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
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Old 06-07-2020, 10:44 AM   #2
flatheadmurre
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Default 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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Old 06-07-2020, 10:47 AM   #3
19Fordy
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Default Re: valid Temp Sending unit test?

Are there any "shorts" in your test circuit the way it's hooked up?
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Old 06-07-2020, 03:50 PM   #4
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Default 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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File Type: jpg IMG_3708.JPG (98.7 KB, 44 views)
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Old 06-07-2020, 05:21 PM   #5
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Default Re: valid Temp Sending unit test?

Well, it sure isn't original, so no telling what it is.
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Old 06-07-2020, 11:17 PM   #6
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Default Re: valid Temp Sending unit test?

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Looks like a stewart warner sender and that doesn´t work with the KS gauge.
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Old 06-08-2020, 12:59 AM   #7
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Default 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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Old 06-08-2020, 08:00 AM   #8
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Default 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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Old 06-08-2020, 09:17 AM   #9
19Fordy
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Default 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.
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Old 06-08-2020, 09:30 AM   #10
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Default 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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Old 06-08-2020, 09:32 AM   #11
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Default 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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Old 06-08-2020, 09:36 AM   #12
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Default 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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Old 06-08-2020, 09:39 AM   #13
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Default Re: valid Temp Sending unit test?

Quote:
Originally Posted by Scott52 View Post
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?
Yours is not an original, looks nothing like an original. Resistance sensors in general do not work will with the K-S gauges, but the temp sensors seem to work better than the other sensors. You need a resistance sensor that is scaled correctly for the gauge. I don't know the answer to which model number that is, but someone here on the Barn should know.

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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Old 06-08-2020, 12:06 PM   #14
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Default 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
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Old 06-08-2020, 03:07 PM   #15
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Default 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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Old 06-08-2020, 03:24 PM   #16
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Default 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
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Old 06-08-2020, 06:43 PM   #17
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Default 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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Old 06-08-2020, 07:27 PM   #18
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Default 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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