Temp gauge works backwards
 

Hey guys, I have a 51 pick up I just rebuilt. Before I started the rebuild the temp gauge went to hot when the key was turned on and than to the Center of the gauge when warmed up. I checked the temp and it's 180 degrees warm. So when I completed the rebuild I changed both sending units with new units from Mac. It still did the same thing so I reversed the location of the wires on the gauge. No difference. Any advice?

Re: Temp gauge works backwards
 

Is your truck 12-volt or six? If it's 12, the voltage reducer for the gauges might be wired backwards, though this is only a guess.

Re: Temp gauge works backwards
 

The temp gauge goes to hot with the key on. Somebody will come on with a more detailed explanation...... Mark

Re: Temp gauge works backwards
 

Here ya go..........

https://www.fordbarn.com/forum/showthread.php?t=85681

Re: Temp gauge works backwards
 

If the wiring from the gauge to the senders is broken somewhere, it will always read hot since the gauge goes to full H when there is no current flow. The two terminal sender unit is a bi-metallic switch that opens the circuit if it reaches a set temperature like just above boiling point. All it can do is give a Hot indication when it opens the circuit. The single terminal sender is the calibrated sender that will give you a C or cold indication when you turn on the key with good connections in the circuit. It has a bi-metallic switch that works in unison with a ground arm and is normally grounded when the unit is first turned on which gives a full C indication (cold) until the engine warms up and allows the sender bi-metallic arm to bend farther away from the ground arm to give a warmer indication on the gauge. Current flow decreases in these units to give a hotter indication on the gauge. It starts cold with high current flow and gradually gets less current flow the warmer the coolant gets.

This is different that the pressure and quantity units that King Seeley made. They have higher current flow with higher pressure or higher quantity. Sort of backward to the temperature reading instruments they made.

The reproduction senders can be problematic. I prefer to find good used or NOS original King Seeley units when I can. Gauges are generally marked for connections on the back. If it works backwards then it either doesn't have the correct gauge or it is turned upside down or something. They always read Hot when Off. When you ground the sender wire it should go to Cold since it will be at full current flow. I wouldn't do this test for long though or it might burn out the heating coil in the gauge.

Re: Temp gauge works backwards
 

Hi there, That is how it is supposed to work. Nothing wrong with it. Don't mess with it anymore, its perfect. Regards, Kevin.

Re: Temp gauge works backwards
 

It would seem to me that it would go all the way to cold when first started and then climb.

Re: Temp gauge works backwards
 

I just went through this. Full hot with the ignition off, full cold when the ignition is turned on, and climbing to a little more than half scale as the temperature rises. Unless a '51 truck has a different system than a car (highly unlikely given the preponderance of sending units), it should work the same. Sounds like the O/P is right in his description; probably newer resistance sending units rather than original "King Seeley" units (which can usually be repaired as I found out about a month ago).

Re: Temp gauge works backwards
 

I'm sorry for not replying quicker but just after posting I got a call my mom was going to the hospital.

Thanks for the advice.When I turn the key on the gauge goes from cold to hot and than comes down to the center of the gauge. When I disconnect the sending it goes to old and than hot when I ground the wire. Exactly opposite of what it should do. The gauges all match and appear original. Does any one know if there's a way to adjust something in the gauge to reverse the needle?

Re: Temp gauge works backwards
 

Your gauge is fine, hope your mom is the same.

Re: Temp gauge works backwards
 

A little history on your pickup might help us. Do you know if the dash speedo/gauge unit was ever worked on or restored? Do you know if the temp gauge ever worked normally during your ownership of the vehicle?

Most all of the Ford/King Seeley engine coolant temp gauges worked the same way in that early 8BA era. If it is reading H or Hot when no power is applied then that is as it should be. If it goes cold when power is applied to a functional circuit with senders connected properly then that is as it should be. If it reads cold power off, then it is likely a gauge from a different system or some sort of repro set up from the modern era.

Re: Temp gauge works backwards
 

No way.

Sal

Re: Temp gauge works backwards
 

King Seeley electric temp gauges as fitted to early flathead Fords with two engine sender units (one is just a switch two terminals & the other single terminal is the sender) work like this. With ignition switch OFF the temp gauge pointer reads to the right side of the dial which is HOT or 212 deg. F. With a cold engine and ignition switch turned ON the gauge pointer will go to far left or cold. As engine warms up pointer will move to the right to read the coolant temperature as it warms up. This is noted in workshop manuals for Fords through the late 30s to the 50s. If the F1 in question has some other type of gauge then it may be different. Regards, Kevin.

Re: Temp gauge works backwards
 

Wmurphy, Maybe you could locate a drivers handbook or a workshop manual so that the original temp gauge operation for your model could be determined. Regards, Kevin.

Re: Temp gauge works backwards
 

Hope I didn't cause confusion in post #3. I knew it went one way with the key and I wrote the wrong way....... I knew there would be more detailed explanations...... Mark

Re: Temp gauge works backwards
 

The gauges all match in Color and design. The speedo is stamped on the back with 1951 but I guess it's possible the temp gauge has been changed.

Re: Temp gauge works backwards
 

Attached pic of my 48 F1 gauges with the POWER OFF. Note the temp gauge position is HOT. Once the ignition is turned on it goes to COLD, and increase as the engine warms up. If you want to check the gauge calibration, disconnect the sender wire and connect it to a resistor of around 45 ohms (other side to ground). It will read around mid position in my experience.
Al

Re: Temp gauge works backwards
 

Sal, so you say "no way" ! So you tell us your version of how this temp gauge should read. We are talking original equipment Ford electric temp gauge here. Regards, Kevin.

Re: Temp gauge works backwards
 

Murphy is claiming that his is working the opposite of normal (post #9):

"When I turn the key on the gauge goes from cold to hot and than comes down to the center of the gauge. When I disconnect the sending it goes to old [cold] and than [then] hot when I ground the wire. Exactly opposite of what it should do."

Re: Temp gauge works backwards
 

Thanks for the input. The gauges all match in style and appear to be the same age so I don't think I want to change the temp gauge. It makes sense now why changing the wires on the gauge didn't make a difference. Does anyone know where I can get a sending unit that would work opposite to the "normal" unit?