The temperature gauge on my '56 Ford does not work.  However: my question is this:  With ignition off (or on for that matter) the gauge reads fully "hot".  This does not seem right.  I sent my cluster out to be refurbished, both cosmetically and functionally and it came back same way, so I assumed it was correct.  Have not purchased new sending unit yet.  Waiting reply here.

Thanks Guys

Disconnect the sender and see if there is a change

This is from the 1953 service manual, however the gauge operating principles are the same for '56. The only difference is the '56 gauges were designed to operate on 12v instead of 6v. The gauge normally rests at the "H" position with the key off.

INDICATOR AT THE "H" POSITION ALL THE TIME

Turn on the ign switch and observe the gas and oil pressure gauges. Engine should be at normal operating temperature. If they are inoperative (I assume yours work) correct the power supply circuit from the ign switch to the instruments. If the gas and oil pressure gauges work momentarily short the wire leading from the temperature gauge to the sending unit. If the indicator stays at the "H" position replace the gauge. If the indicator moves toward the "C" position an open circuit is indicated.

Ed. note: if an open is indicated it could be in the wiring, the sending unit or the gauge. To check the wire use a volt/ohm meter set for continuity with the wire disconnected at both ends. My manual addresses testing the sender and the gauge but it involves substituting know good parts. I kinda doubt you have a known good sender and gauge lying around.

Suggestion- Buy a NOS Original Sender not a Repro. Last One I purchased did not work. A NOS One worked fine..With no Power the Gauge reads "H". Power applied with Key in "Run" Position the Needle slowly moves to "C". If Your Gauge reads "H" with Key "On" then You may have a bad Gauge or Sender. Ground the Sender Wire Terminal with Key on and see if Gauge moves to "C".If it moves your Sender is likely at fault.

  

I've tested the gauge with a 9 volt battery and had luck.
Also, I've been sending gauges to Bob's Speedometer in Howell, Michigan for years with no complaints.
They fix 'em and I install 'em.
bobsspeedometer.com
Tim
Wrinkle City, Florida
33706

It was Bob's Speedometer who refurbished my cluster..

Please remember if you have a Pertronics ignition do not leave it run very long without the engine running.. If the gauge does not move very quickly off the "H" then start looking for the problem. Good Luck 
PS I had more problems with the tank float than the sender or the gauge especially getting a near correct reading.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Okay about Bob's Speedometer.......
They repaired my temperature gauge and it stays on COOL until the temperature gets to 190 degrees. Then it read 1/4 on the gauge. Around 195 degrees 
it will read 1/2 on the gauge.
I have and after market set up with three readings: Temp, Volts and Oil and an electric fan that is never on when doing 70 mph on I-75. Some times it is turned on when I wait at long traffic lights in the city in the summer.
You might let you car get warm and see if your gauge will move just a little.
good Luck
Tim
Waiting Room for Heaven, Florida
33706

i want to close this one out.  I replaced the temperature sender and everything works fine.

Thanks guys..

ONE FINAL ENTRY!!  Temperature sensor calibration

When I said everything now works fine, I meant when I turned on the key, the temp needle swung to the COLD side.  However after a short drive the needle gets penned up at the hot position.  There is no indication the engine is overheated so I assume the sensor is out of calibration.  Called Mac's (where I bought it) and they gave the following information which should be very useful to other members.  Haven't checked it yet.

Engine cold      14-20 ohms
160 deg            35 ohm
175 deg            50 ohm
212 deg            open circuit or infinite ohms