Did you use teflon tape on the threads? They are a tapered pipe thread, and should need nothing to seal them. The thread into the head creates the ground, and is necessary to work correctly.

Thanks, Dany. I've had the car for a year, and have not swapped out the sensor. I do get good (zero resistance) contact from the sensor body to the block. The readings on it are ca 2500 cold to ca 300-400 after a five minute + warm up. The engine does not overheat at all.
Interestingly, I do have a slight (one ohm) reading from the battery terminal to the car body and engine block and am installing a new and hefty woven cable from the battery to the block, etc. I had previously, and very adequately, replaced much of the sad wiring harness. My starter, lights, blower, horn, etc. seem quite normal. Obviously, perfect continuity is what we are after.

Thanks again for your insight.

Terry

Does this 1950 Commodore have the narrow block 232 and head, or has a later wide block 232 and head been transplanted in it? In 1950 the temp sender had a 3/8 NPT thread and was a large bulb type bimetal sending unit. The bimetal unit does not work through varying resistance, but by the bimetal contacts pulsing (opening and closing) in harmony with contacts of the bimetal strip in the King-Seeley dash gauge. In 1951 with the advent of the 1/4" wider blocks and heds, Hudson started using a variable resistance type sending unit with a smaller 1/4 NPT thread, the "probe" is much shorter on this newer sender than the old bilmetal unit. The correct sender for the 1951-56 wide block/ head engines is Standard Motor Products TS4, or NAPA Echlin TS6464. The correct sender for the 1948-50 narrow block and head is 3/8 NPT, and is only available as good used, NOS, or a repro unit from KM Lifestyle (Kevin Marcinkus) in Auburn, MA You can visit the KM Lifestyle website here: https://mykmlifestyle.com/
 

Kenneth,
Some research to do on my part. The sender is at the firewall end of the head which lends me to believe it is a later engine. I'll pull the sender this eve to get a visual. Fortunate in that I don't have to bend my body around the hood support.
Incidentally, after installing the fresh battery cable and insuring all tie points are electrically secure everywhere, I did note a very slight fluctuation on the gauge when moderately revving the engine.
Even though I have long time experience in servicing vintage radios, including car radios of this period - and was born before this car came off the line - I am truly a newbie regarding Hudsons, and am learning as I go.
Thanks for the education. I'll keep you and Dany posted.

Ohms @ Temp values for SMP TS-4 and ECH TS6464 senders

Ohms     Temp
221.3      73˚
112.1      103˚
88.8        114˚
71.5       124˚
55.4       135˚
45.6       144˚
37          150˚
32          157˚
27          167˚
23.5       180˚
22          185˚
20          194˚
19          200˚
17          203˚
14.5       212˚

Thanks Kenneth! This data is very helpful. The old sender appears to have been painted along with the engine. An original part perhaps? A swap looks to be in order.
Terry

Terry, one more thing, does your 50 Commodore still have the original 1950 Fuel and Temp gauge cluster? IF SO, the original 1950 TEMP gauge operates backwards of the 1951-53 TEMP gauge. In the 1950, the needle of the TEMP gauge parks on HOT when ignition is turned off, due to the original narrow block engine using the bimetal contact type bulb sender I previously mentioned. The 1951-53 TEMP gauge parks on COLD when the ignition is shut off. SO......if you have the original 1950 Temp gauge hooked up to the 1951-56 Thermistor type sending unit, it will not function correctly. The needle will not budge from HOT until after the engine warms up, and then will creep towards COLD as the engine heats up. Fortunately the 51-53 King -Seeley Temp gauge can be fitted to your 1950 cluster.
 1950

1951
 

Good info, Kenneth. Yes, it does have the original cluster. The needle did move, albeit slightly, towards cold as the engine spun and warmed. An interesting and easy thing to try would be reversing the connections on the gauge. I thought I could get to the project this evening, but doesn't work out. Saturday for sure. I really do appreciate your knowledge and help! Great pictures too!

Reversing the connections will not change the reading, as it is a bimetal type gauge, not electromagnetic. The needle movement is caused by the bimetal heater strip, with it's fine filament heating up and curling. The filament and heater strip will heat up and curl the same way regardless of current direction / polarity.
    

This electrical information and the illustrations are most helpful. The exam begins later this afternoon. As mentioned, I restored numerous tube-type car radios over the years and disassembled and rejuvenated vibrators when they were an operational necessity - long before the original radio chassis became obsolete and discarded. In my opinion, the muted sound of the vibrator is unique, and appropriate to all sounds throughout a vintage car.
A clever engineering design on the heater sender too.
Your knowledge and participation is most appreciated!