53 Mercury temperature gauge

dean333

dean333

Well-known member
With the ignition off, the needle is above the”H” as it should be. Upon start up cold, the needle is just above half. As the engine warms up, within 5 minutes, the needle gradually rises back up past “H”. I’ve replaced both sending units to no avail. Suggestions?? Thanks. Oh, I should mention a previous owner has changed it from 6V positive to negative ground.
 
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The senders are pipe thread and the factory installed them without any thread sealant. If you used any teflon thread sealant tape, it's best to remove it from both senders and reinstall them with no sealant. They need a good ground in order to work properly.
 
Ok, I’ll remove the thread sealant and retry. Thanks! On second thought, I’ll run ground wires to each unit and try that first.
 
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Rather than pull the senders out and cleaning off the sealant, I ran jumper wires to ground from the housings, same result within five minutes of running.
 
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All sorts of stuff that may help you here...
post-30763-143137903585_thumb.jpg

The two prong unit is really just a normally closed switch, when cold it should read 0 ohms, when the engine gets to hot it opens and the gauge reads hot...
https://forums.aaca.org/topic/86122-ford-flathead-temp-sending-units/


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Pete, I looked online for it. All I could find was that service bulletin number updated to modern Fords.
 
dean333 said:
Pete, would you kindly email me those bulletins so I can print them out? Thank you.
Hoesa81@yahoo.com
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Tim,
Right click on the image you want and you should get a drop down menu giving you the option to "Save image as". Select that option and save it to your computer in your Pictures files. From there you should be able to select it and send to your printer.
 
19forty, I was referring to the dash gauge. They look similar, the Lincoln gauge has an “l” on the face which may be hidden when mounted under the dash face or simply painted over with a dab of black paint.
 
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dean333 said:
19forty, I was referring to the dash gauge. They look similar, the Lincoln gauge has an “l” on the face which may be hidden when mounted under the dash face or simply painted over with a dab of black paint.
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You can get it and if for some reason it doesn't work you can return it, unless the seller has a no return policy. I feel your pain, I gave up on tiring to get my temp gauge to read, what i would consider correctly, (in the meddle of gauge). It reads 3/4 up the gauge during normal running. I also have mechanical temp gauges on the car (and the hand held tempatire gun) so I can compare them, I have tried replacing the gauge and the sending units, all to no avail. I have considered installing a small resistor in the system to see if the would help.
 
Merc Cruzer said:
I have considered installing a small resistor in the system to see if the would help.
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Adding a current resistor would make it worse. Temp gauge rests at the "hot" position, then current flow moves it lower.

I suspect you and the OP both have aftermarket senders, which work on the resistance principal rather than the timed-pulse principal of the original K-S sender. I don't know how to get gauge accuracy with modern senders.
 
JayChicago said:
Adding a current resistor would make it worse. Temp gauge rests at the "hot" position, then current flow moves it lower.

I suspect you and the OP both have aftermarket senders, which work on the resistance principal rather than the timed-pulse principal of the original K-S sender. I don't know how to get gauge accuracy with modern senders.
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Jay,

Now that you mention it you are correct as to adding an resistor would in fact make it worse.

You mention "after market senders". These are what I am running in the car with the gauge. I also have 2 other gauges that I have used with these sending units. to no avail.

I will add the pictures as soon as I can figure how to remove the "Sorry, you have been blocked
You are unable to access fordbarn.com" notice.

They are rexactialy as pictured in post #6.
 
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