What Temperature Sending Unit do I need?

[Ken T]

I bought the 1940-1955 Temperature Sending Unit (6-Volt) (Single-Post) from Early Ford Store. Everyone sells the single and double post unit. The one on my truck is a single post. The unit on my truck is much larger than the one I received. I don't see any other options than the two for sell at any stores online. Does anyone know where to purchase a proper replacement? This is what's in the truck and the other is what I bought.

Distributor 1.jpg Screenshot 2024-05-12 200101.jpg

[69a]

That is not the sensor. It should be in the head, next to the top radiator hose.

[Lanny]

I would think that a NAPA auto store might be able to get them.




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[tubman]

Most Ford V8's have both a single post and a double post unit. The single post unit is in the passenger side head, and is the actual sending unit. The two post unit goes into the left head, and is normally closed, passing the input from the actual sending unit to the gauge. The double post unit is just a switch that will open up when an overheating condition exists and will send the gauge to full hot. You can run with one sensor, but it has to be the single post.

The sensor you picture appears to be the correct one. Be aware that the aftermarket sensors are usually of inferior quality, which is why I save every original Ford piece I can find.

[Ken T]

Oh okay, I see it now. It's on the driver side head. What is the part above the distributor? Unfortunately, I only have a few hours on Sunday's to work on my truck and it's a 90 miles drive to get there. I have to rely on the pictures I've taken to reference what I need.

Heads (3).jpg Electrical - Temperature Sending Unit.jpg

[69a]

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Drain about 5 quarts of fluid from the radiator, and remove the old sensor. Your local auto shop should be able to supply you with an adaptor if your replacement doesn't fit.

[Ggmac]

Have you determined that the original sender is bad ?
The piece above the distributor is the vacuum brake . It is used to limit your distributors spark advance .

[drolston]

Run a test. With the ignition switch off, the temp gauge should read full hot. If not, the gauge needs repair or replace. Turn the ignition switch on; if the engine is cold, the temp needle should move slowly to cold. If not disconnect the wire at the single pole sensor and hold it to ground; the temp needle should move slowly to cold. If not, short the connection between the two poles on the double pole sensor (generally the one on the driver side). If that gets the needle to move the double pole sensor is bad and can be bypassed (connecto both wires to the same/either post) or replaced. If it still does not come off of full hot, put an ohmmeter between the single post sensor post and ground; If it reads open circuit, that sensor is bad; if it is not open circuit, check the continuity of the wire between cylinder heads and the wire from the driver side sensor to the temp gauge under the dash. To do that ground the end of the wire at the engine driver side, and then check the other end of that wire at the gauge with an ohmmeter; should read near zero ohms; if open circuit, the wire is bad (rare). If the wires are good, it may be the gauge or lack of power to the gauge. Disconnect the wire at the driver side sensor to create and open circuit there. With the ignition on, you should have 6 volts at both terminals on the back of the temp gauge. If you have 6 volts at only one terminal the gauge has gone open circuit/bad. If you do not have volts at either terminal something has come disconnected or broken between the gauge and the ignition switch terminal. Some instrument arrangements have power to two gauges jumpered together with a short strip. Check that too.
Good luck. You are going to need that temp gauge!

[19Fordy]

Drolston, THANKS for posting that excellent diagnosis procedure.

[Ken T]

Drolston, thanks for the very clear info on the how to proceed. I wouldn't even know where to begin. Now I do.

[51woodie]

Ken. Here is the temp circuit diagram, and pics of the single and double contact sensors on my 59AB.

[petehoovie]

Originally Posted by 51woodie

Ken. Here is the temp circuit diagram, and pics of the single and double contact sensors on my 59AB.

[Ken T]

Originally Posted by 51woodie

Ken. Here is the temp circuit diagram, and pics of the single and double contact sensors on my 59AB.

Thanks 51woodie. Pictures help a lot!