I am working on a 1950 original gauge cluster. I have converted the truck wiring to 12V but am using a solid state 12 to 6 volt reducer from D. Carpenter. The output of the converter is set to about 5.8V. I have the original style temperature sending unit (new) and a 160F thermostat. The temp gauge when the engine is at operating temperature (160F verified with an infrared temp probe) is just a shade higher than the cold reading. I expected it to read about half way between the "C" and mid-gauge since 180F is normally half way. Could the slightly low voltage of the converter be the problem? Anyone else see a low temp gauge reading and found the problem? Any suggestions?

 

You should shoot for an operating temp of at least 180, or you'll create sludge.

I have a solid-state regulator and set it at 7.2 volts, which is what a 6v gen puts out at cruise speed. Honestly, the gauges don't seem very sensitive to voltage, which is one of the virtues of the King-Seely type gauges.

 

Well, I could change the thermostat to a 180 and hope the gauge reads around mid gauge. My manual shows the 160F as the "summer" thermostat, 180F as the "standard" thermostat, and the 195F as the "winter" thermostat. Since the truck is driven in summer, I have the 160F. Aside from changing the thermostat, any other suggestions?

 

I'd test the thermostat in a pan of water. A 160 stat should begin to open at 160, not operate there. Lots of variability in stats these days.

 

OK, then your theory is that the gauge is probably OK, it's the engine actually running too cool. I ordered a new 180F thermostat so I'll give that a shot. If that reads at least to the 1/4 point, that will work for me. I hope this works!

 

Doug, I have an infrared test gun if you need it.

 

Thanks, Pete but I already have one myself. That is how I verified that the problem was in the gauge setup and not my engine actually not heating up. I ordered a 180F thermostat and will install to see where that temp puts the gauge and then go from there.