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Old 12-12-2017, 02:14 PM   #1
homeboymi
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Default Temperature Sender Wiring

I'm trying to fix the temperature gauge on my 40 Ford. It reads H at all times. There is only one temperature sensor on the left bank. I see it is wrapped with teflon tape. That may be my problem (no ground)as I have read other posts on this forum.

I found a NOS temperature switch in my trunk. It is wrapped in wax like paper and is brand new. I plan to install it on the left bank where the gauge wire is and put the temperature sender on the right bank. I would appreciate a photo of the wiring from the right bank to the left bank so I know the route that was original to this car.

I am very grateful for this forum.
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Old 12-12-2017, 02:26 PM   #2
supereal
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Default Re: Temperature Sender Wiring

There should be a temp sensor in each head. The one with one terminal is connected to one of the terminals on the sensor with two terminals. The remaining terminal goes to the temperature gauge. The only variable sensor in the one terminal type. The two terminal sensor contains a bimetal switch that opens when the temperature reaches the boiling point, opening the circuit and sending the gauge to the "hot side" of the dial. The two sensors are connected with a short wire between them that crosses the engine.
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Old 12-12-2017, 02:59 PM   #3
JSeery
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Default Re: Temperature Sender Wiring

Not likely it is grounded through the tape on the threads.
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Old 12-12-2017, 06:02 PM   #4
Ross F-1
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Default Re: Temperature Sender Wiring

Quote:
Originally Posted by JSeery View Post
Not likely it is grounded through the tape on the threads.
If the sender that's installed is the 1-terminal type, running a jumper from the body of the sender to ground will quickly verify.
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Old 12-12-2017, 06:18 PM   #5
Paul Bennett
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Default Re: Temperature Sender Wiring

Not having a '40 F I can't provide a visual but I can provide a verbal. The wire from the temp gauge passes through the firewall and connects to one terminal of the dual terminal sensor in the drivers (left) head. A short piece of wire is connected to the other terminal of that sender and goes across the engine under the generator to the single terminal sensor in the passenger (right) head. If it still doesn't work, do the battery test connecting the wire from the gauge to one cell of a flashlight battery connected to ground. The gauge should read mid-scale. Grounding the gauge wire should make the gauge read near the bottom ("L").

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Old 12-12-2017, 07:07 PM   #6
homeboymi
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Default Re: Temperature Sender Wiring

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I went out and removed the teflon tape. Gauge still remains past H. I disconnected the wire to the temperature sensor and did the battery test as recommended by Paul. The gauge slowly retreated towards the C stopping close to the middle.

Last edited by homeboymi; 12-12-2017 at 08:06 PM.
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Old 12-12-2017, 07:37 PM   #7
JSeery
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Default Re: Temperature Sender Wiring

Yep, the gauge passed the test!
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