So it's kind of hard to explain and actually believe but i have something strange going on with my temp sensor:

the connector broke of (nothing strange here) because the Vbelt (multiV) broke.
so i currently have no temp sensor connected but when i start the car the dial shows cold and after the exact same amount of time running the temp starts to climb to normal (N) as it does when the sensor is connected.
now i will be installing another engine soon (have a piston with a hole in it ) but i don't trust the temp reading anymore. anyone had this before?
or any idea what ghost i'm after?

 

The temp sensor - located above the thermostat housing - tells the computer if the truck is warmed up yet or not.
The temp sender is located elsewhere (on a 302, it would be front left of the intake between the 1st and 2nd bolt) sends a signal to the gauge on your dash. Two separate systems going on there.

 

it is a 300 inline 6. so the actual water temperature readout on the gauge doesn't come from the water? The readout from the water that goes to the ecu is probably for fuel mixture then?

thanks

 

There are 2 units - they both read the coolant temp. 1 is a sensor which sends a signal to the ECU. The other (separate , different) unit is a sender - it operates the gauge.
The sender is pretty much the same as what the earlier motors had on them to operate the temp gauge.
With the addition of EFI and ECU's they installed a temp sensor - tied into the ECU circuit to tell the ECU what the temp is. The sensor is a complicated little piece of electronic wizardry.
The sender is a basic little unit that works kind of like the oil pressure sender - it just has to operate a simple gauge.
The 2 units are on different circuits - totally unrelated to each other. So having the gauge act up will have no bearing whatsoever on how your engine management system works.
On the other hand having your sensor act up would feed wrong signals to the ECU and that would have a bearing on how the system behaves.

 

thanks for the explanation, although i feel a little embarrassed i'm glad that my gauge isn't acting off. the coolant temp sensor for the ECU is broke but that's no big deal. normally in a week or to the car gets put aside for an old new engine.