411 S3 temperature gauge sender

[Green411]

Has anyone got a part number/supplier for a 1/8 NPT temp gauge sender that gives the right reading on a 411 S3 please?
I had to move mine when I fitted Holley Sniper, as the Coolant Temp Sensor for the ECU has had to go where the original temp gauge sender lived. So the sender now has to go into the 1/8 NPT horizontal port just in front and to the left of the original port.
I read that the colour of the insulator denotes the resistance but that doesn't seem to be the case. The original was black, and a Jensen Healy uses a black 1/8 NPT sender so I bought one, and it read c. 60-70% of the original.....
Thanks
Mark

[David C]

If you still have the original sensor and own or can borrow a multimeter you can measure resistance at 1 degree, 50 degrees and 100 degrees. I have seen 1/8NPT sensors for sale showing resistance at these temperatures.

[Green411]

Hi David/all
I keep everything, which of course means I can never find anything! That includes the original tamp switch, which I only took of a month ago.....d'oh....
I found part number 911-1-35052 on an invoice in the history file for my car & used for a replacement temp switch. But there's no guarantee that's the right number (although it was Bristol who fitted it so I hope it was right!) & searching on that number brings up nothing useful.
Have also tried to plot a resistence curve, with limited success:
80*c = 87 Ohms
77*c = 91 ohms
75*c = 100 ohms
70*c = 121 ohms
60*c = 165 ohms
50*c = 250 ohms
The temp gauge always seemed read a bit high - just above halfway, between 90 & 100 at normal open road speeds. About 3/4 of the way up the gauge when the fans came on (98/93* switch in top rad tank)
Cheers
Mark

[David C]

Here's one with 1/8NPT thread that seems to have the same resistance as yours:

https://efi-parts.co.uk/product/univ...ensor-1-8-npt/

[Green411]

Thank you! It looks like a 2 pin CTS for the efi's ecu though, so do you happen to know if it would work in place of an old fashioned single terminal gauge sender?
What did you use as the search criteria? I ask because I've spent hours looking on the web for a temp gauge sender with that resistence and got nowhere, and you did it in about 10 mins flat....

[David C]

I searched for 1/8 NPT temperature sender. My guess is that you can ground one terminal and use the other in place of the original single terminal. I imagine it's plain DC resistance so should be able to use either terminal but best to use ohm meter to check whether one terminal is already grounded.

[Green411]

Have found the right sender. Merlin Motorsports in UK sell a 1/8 npt sender for Smiths gauges. Bought one and it works fine. Dunno why I couldn't find it in earlier searches though.......d'oh.................