1955 Fuel gauge, speedometer & temperature guage not working

[dcplums]

Fuel and temp guage not working. have not chedked the temp guage but have grounded the fuel guage wire at the sender and gauge goes to full. Also have 5.8v at sender. Removed sender and cleaned all ground connections. Sender is grounded. Still nothing when key turned on. Removed old sender and installed new one. Turned on key and guage still reads empty. Tank is 1/2 full. I know previous owner was messing around with speedometer and had disconnected it as it was noisy. Maybe he did something in behind the dash?? Starting to get frustrated with this one.

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[Louis]

Fuel and temp guage not working. have not chedked the temp guage but have grounded the fuel guage wire at the sender and gauge goes to full. Also have 5.8v at sender. Removed sender and cleaned all ground connections. Sender is grounded. Still nothing when key turned on. Removed old sender and installed new one. Turned on key and guage still reads empty. Tank is 1/2 full. I know previous owner was messing around with speedometer and had disconnected it as it was noisy. Maybe he did something in behind the dash?? Starting to get frustrated with this one.

You have a "Instrument cluster constant voltage" source. CVS (10804 @ Classic Auto) that controls the fuel and temperature gage. It feeds off the "A" connection of the ignition switch. This could be bad.

 

[Tom Alpers]

I didn't think the 55's used a cvr. He stated in his post that he's getting 5.8 volts back at the sender which makes sense on a 6 volt system.
I'd take a look at a wiring diagram and trace the wires, something must be disconnected, misconnected, or broken. The temperature gauge power feed comes from one of the terminals on the back of the fuel gauge. That terminal is feed 6 volts from the ignition switch. That 6 volts is supposed to feed thru the fuel gauge and on to the fuel level sender. As the fuel sender resistance changes it changes how much current flows thru the fuel gauge and makes the reading change. The temperature gauge takes the power feed and runs it thru the temp gauge and from their out to the temp sender on the engine. Similar to the fuel sender, the temp sender resistance changes which changes the temp gauge reading. No CVR anywhere in the circut for the 55's.

 

[dcplums]

In the 55 shop manual is says that V8 engines have a thermal switch (2 connections) and a sending unit (1 connection), one in each head. I located the thermal switch in the left hand head but cannot find the sending unit in the other head. ??

 

[cokefirst]

The Thunderbird had a single sending unit. The shop manual may refer to the passenger car and not the Thunderbird. Up until 1957, Ford used King Seeley gauges. These work on a different system. It an be confusing to those of us with limited electrical knowledge. An earlier comment is correct. Ford did not use a constant voltage regulator until the 1957 model year when they used resistance as the gauge function.

 

[Louis]

You have a "Instrument cluster constant voltage" source. CVS (10804 @ Classic Auto) that controls the fuel and temperature gage. It feeds off the "A" connection of the ignition switch. This could be bad.

Sorry I was basing my post on my 57 which had a similar issue and assumed(AOYAM) 55 & 56 would be same.

 

[doug7740]

The Thunderbird had a single sending unit. The shop manual may refer to the passenger car and not the Thunderbird. Up until 1957, Ford used King Seeley gauges. These work on a different system. It an be confusing to those of us with limited electrical knowledge. An earlier comment is correct. Ford did not use a constant voltage regulator until the 1957 model year when they used resistance as the gauge function.

There is no similarity in the temperature sensors for the 1956 and 1957 Thunderbird.

* The 1956 temperature sensor has a power regulator designed into it and it works with a 40-ohm temperature gauge.
* The 1957 temperature sensor is only a temperature sensitive resistor and requires an external power regulator (CVR) constant voltage regulator. It works with an 11-ohm temperature gauge.

Although the 1956 temperature gauge and the 1957 temperature gauge look the same, they are not. The 1956 temperature gauge is 40 ohms, and the 1957 temperature gauge is 11 ohms. Same goes for the fuel gauge and sender.

doug7740
1955 Thunderbird Blue

 

[doug7740]

I didn't think the 55's used a cvr. He stated in his post that he's getting 5.8 volts back at the sender which makes sense on a 6 volt system.
I'd take a look at a wiring diagram and trace the wires, something must be disconnected, misconnected, or broken. The temperature gauge power feed comes from one of the terminals on the back of the fuel gauge. That terminal is feed 6 volts from the ignition switch. That 6 volts is supposed to feed thru the fuel gauge and on to the fuel level sender. As the fuel sender resistance changes it changes how much current flows thru the fuel gauge and makes the reading change. The temperature gauge takes the power feed and runs it thru the temp gauge and from their out to the temp sender on the engine. Similar to the fuel sender, the temp sender resistance changes which changes the temp gauge reading. No CVR anywhere in the circut for the 55's.

doug7740
1955 Thunderbird Blue

 

[Tom Alpers]

Temperature sender sensor difference between the 55 56 57. Note in an earlier comment it was mentioned that one of the sensors was 2-terminal. The pre-57 had two terminals but they were both connected to the same rivet from what I can see on the photo.

 

[dcplums]

I have concluded that my engine has been upgraded to a 56 or newer, and that is why there is only 1 sensor location (driver's side). The question now is, will a 55 temp sensor (not thermal switch) work in the newer block along with my 55 gauge?

 

[Tom Alpers]

I have concluded that my engine has been upgraded to a 56 or newer, and that is why there is only 1 sensor location (driver's side). The question now is, will a 55 temp sensor (not thermal switch) work in the newer block along with my 55 gauge?

If you still have the 6 volt gauges and the threads in the bung are the right size for the 55 sensor, I don't see what not.

 

[cokefirst]

The 1956 temperature sending unit is identical, except it is 12 Volt. That would mean that your bung is the correct size. simply put in a 6 volt sending unit and you should be good.