Another Flathead temp sender question

1oldtimer

1oldtimer

Well-known member
I've read a bunch of posts and maybe I missed it, but what do the stamped numbers on the senders themselves mean.
 

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i've heard tell it relates to a generalized part number sometimes referred to as a "Industry Standard Cross Reference Number" . which would explain why they all bear, as an aftermarket product, the same number. that's my guess anyway, FWIW. :)
 
Assuming these are "Ford", with stock flatheads using two sensors that have different functions, can't tell which of them are for "what". My '47 sensors have screw terminals and are wired in series. I understand passenger side regulates the temperatuire display on the dash gauge and driver's side only senses overheating and causes the dash gage to go to "hot". I think units with electrical tab connections on top may be 1949 or later ?
 
My very original '51 had screw terminals, and just about every 8BA unit I come across does as well. (I run into a bunch, buying and selling aftermarket heads.) I think "hueyhooligan" is correct in referring to them as "aftermarket". It seems obvious that the one on the left is a "sensing" unit, while the three on the right are "switches".
 
According to Mr. GOOGLE the 233 means:
The number 233 stamped on a 1949–1953 Ford temperature sending unit is an old Ford/Mercury part identification or engineering number (not a temperature or ohm rating). Often paired with an "KS" stamp, these units are designed to measure the coolant temperature for your vintage dash gauge.

Here's some info. about Thermostat Temps: Look at Posts 30 and 31.
https://www.fordbarn.com/forum/showthread.php?t=102106&page=2
 
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One is a current pulse unit for approximate temperature (one terminal) and the other is just a temperature sensitive on/off switch for overtemp (two terminals). This way both banks would be covered for overtemp with one actually giving an approximate temp indication. Both work with bi-metallic switching. Anything above 212 will be caught on the temp scale but both will eventually give a full hot indication. Coolant under 11 or more psi can go over 212 without boiling, but it will eventually will reach a boiling point and overpower the radiator cap. A person would have to perform a test to see what actual temp would activate the two terminal off switch that makes the gauge go full Hot. It may in fact be near 233 degrees F. The two different senders wouldn't have the same part number.

King Seeley gauges always indicate full Hot until the ignition switch is turned On.
 
I really wanted to make sure they weren’t year or gauge specific. I bought a lot of about 10 them, some dual terminal and some single. I did see the KS stamp on them also (some), we’ll see when the get here.
 
Just to add, King Seeley also marked there pressure sending units with the pressure they were designed for. They changed them around 1940 or 41 from 50 psi to 80 psi so they stamped 50 or 80 to tell the mechanic which one it was.
 
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