Temp Gauge hot all the time

[whb52ford]

My car temp gauge keeps reading like it's overheating, but it's not.
I have replaced the temperature gauge and replaced two (not cheap) temp sending units.

My guess is it's the temp sending unit. When I replace the temp sending units, it works for about two months, them the gauge reads overheating, even when the car is cold.

Does something need to be cleaned on the temp sending units. Can't afford to buy a new one every 2 months.

[rockfla]

Originally Posted by whb52ford

My car temp gauge keeps reading like it's overheating, but it's not.
I have replaced the temperature gauge and replaced two (not cheap) temp sending units.

My guess is it's the temp sending unit. When I replace the temp sending units, it works for about two months, them the gauge reads overheating, even when the car is cold.

Does something need to be cleaned on the temp sending units. Can't afford to buy a new one every 2 months.

Not sure IF this will help BUT it was cut off a little so its how I got it, I didn;t apply to my particular set up BUT maybe yours? Is it possible you have a bare spot in the wires somewhere and its grounding out OR at the point of connection possibly touching, heater outlet....or something of that nature cause the circuit to ground????

[whb52ford]

I have the 6 cyl so I only have one post on the sending unit. Your thinking I have a bare spot on the sending wire heading to the gauge. I'll check that now.

thx

[Kube]

Are these repop units you are purchasing?

I trust you did not use any sealant at the block / sending unit. The sending unit needs to ground.
I might suggest you temporarily add a ground wire to the body of the unit - the other end to the block just to see what happens...

[rockfla]

Originally Posted by whb52ford

I have the 6 cyl so I only have one post on the sending unit. Your thinking I have a bare spot on the sending wire heading to the gauge. I'll check that now.

thx

You might be experiencing what I did with our 39 Mercury, IS the sending unit you are using the "one" tang version like on the "left" of my posted diagram or is it the "two" tang version on the "right". I was sent the two tang version by mistake (as replacement) when I "needed" the single tang version so IF you have a two tang version "then" that is your problem!!! AS Kube posted above, you can also try that IF you have the "proper" temp sending unit!!! Sorry, on this form I always think V8!!!

[whb52ford]

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I checked the wire from the sending unit to the gauge. It looks good and is connected to the back of the gauge. I also ran a wire from the ground (+) to the sending unit and no change. Can I put the (-) from the battery on the sending unit center? What would that tell me?

[51woodie]

52ford I'm assuming by your Avatar, that you have a '52 Ford, 6 volt - ground, and I'll make another assumption that the dash gauges operate the same as my '46 Deluxe. Ford designed the gas, oil pressure and temp gauges to be "fail safe". In other words, if a wire became disconnected; gas = mt, oil press = 0 and temp = H. The temp gauge circuit is powered up when you turn the key on. As in the above posted drawing, the wire from the gauge goes to one terminal on the double terminal sender (read switch), which is like an on/off switch. It opens when the engine temp gets too high on that side of the engine. Another wire goes from the opposite terminal to the right side temp sensor, which is the unit that actually causes the gauge to show the engine temp. If any of the connections are poor, or have failed, the gauge will read HOT. You can test the left sensor with a multimeter (wires disconnected) and it should test as a closed circuit. I don't know how to test the right side sender, other that to put a jumper across the terminals of the double sensor and see what you get for a temp gauge reading with the engine cold. Start and warm up while watchin for needle movement.

[whb52ford]

Mine is a 6 so I only have one terminal on the temp sending unit. How do I test that?

[whb52ford]

I took my meter and checked that the sending unit was grounded and it is. The meter reads 1 and .000 when I touch the grounded sending unit. When I check the center of the sending unit I get .014. If it were closed it should be .000 showing no resistance. Correct?

[rockfla]

I don't think that running power to the center of the sending unit will do anything for you, the sending unit "is" a switch (for lack of a better term) and thus a "go" "no go" control. I would think that IF you take the sending unit out and get a glass of "boiling water" and suspend the unit into the boiling water, then take a continuity tester and put one on the "tab" of the unit and the other to "ground" it should "beep" or read continuous current (if switch closes on hot/vice versa if switch closed cold)!!! IF that is the case then your next suspect is your gauge!!! Given all the associated wiring is "good" and not compromised or grounding out!!! The "other" thing you may try as well IS check the wires with a volt/ohm meter and make sure they are solid and "contiuious" as well i.e. "not broken" since it worked for a period, then not, maybe you have a broken wire within the sheath? That's my "logic stab" at it!!!! AND hopefully "Kube" will educate my "limited" brain if I am wrong.

[whb52ford]

I pulled the wire off the sending unit and connected it to the (-) from the battery and the dash gauge immediately went to cold. Where it should be when the car starts running.

I then put the wire from the sending unit to my volt meter. It read 0V. I turned the key and it went to 6.something volts.

I thinking the wiring is good. Why do these sending units only last a few months? Can I hit it with a big hammer to fix? Only kidding, but they are not lasting.

My sending unit (switch) is partially open at .014. Is that correct?

[rockfla]

Originally Posted by whb52ford

I pulled the wire off the sending unit and connected it to the (-) from the battery and the dash gauge immediately went to cold. Where it should be when the car starts running.

I then put the wire from the sending unit to my volt meter. It read 0V. I turned the key and it went to 6.something volts.

I thinking the wiring is good. Why do these sending units only last a few months? Can I hit it with a big hammer to fix? Only kidding, but they are not lasting.

My sending unit (switch) is partially open at .014. Is that correct?

SORRY, I never ran any voltage checks to be able to intelligently answer your question.

[flatheadmurre]

I can only repeat what Kube already asked...Is the sending units newly made aftermarket versions ??
They have 2 tiny PTC resistors in them and fry...
If so invest in a NOS or good used sender !!

[whb52ford]

Yes, these are aftermarket ones. Think from Mac's. So there are resistors in them. Did not know that. That makes sense.

I'll start looking for a NOS.

Is there anything unique to these? Could I use a 6v tractor sending unit?

[flatheadmurre]

Check with the NOS and trusted vendors on here...
Sender must be a King Sealey that´s what ford used.
Or a good used tested one.

[whb52ford]

Thanks for that important info. Will look for a King Sealey. Was not aware we had trusted vendors on here. Where do I find them?

[koates]

Whilst all the above posts are useful there is a very simple way to test your temp gauge. First disconnect the wire from the centre terminal of the sender unit and leave it not touching anything. Turn ignition switch on and the gauge should read hot. Turn ignition off and then connect the sender wire to a good clean metal ground on the engine block. Turn ignition switch on and temp gauge should read cold. As others have said the new replacement sender units have proved to be troublesome so find a NOS or good used unit. Try Michael Driscoll at Third Generation Auto in Ten. He posts on here as 1935fordtn. Regards, Kevin.

[whb52ford]

Thanks, the gauge is working fine.

I will contact Third Generation tomorrow. Thanks for the lead.

[tubman]

Or maybe "Southside Obsolete" ("barnfind 08" on this forum). He mas LOTS of original parts

I was able to disassemble one, clean it up and file the points and got it working properly. The hard part was getting it back together and making it look original.

[whb52ford]

You got my interest. Do you remember how you disassembled it? I would love to see what is inside one and if I could fix it, even better. How do you take it apart.

I found Southside Obsolete phone number and will call them tomorrow. Thanks for the tip.