Ok story goes, swapped in a Cluster with tach and Gauge instead of idiot lights. Switched out the the TEmp sender from idiot light, to one for a guage. Single wire on both of them. Now the temp guage goes up all the way to 125c, yeh Im canadian which is 257f well above the ecm's limit of 220f. Electric fan does not come on, Relay is ok.

So my question is, does anyone know if the the Idiot light sender unit, just sends a On / Off pulse to the ECM to tell it to turn the fan on, then the ECM turns the fan on, and if switching to a Guage sender instead fouls up the readings .

Note read as many post as I could,

Power at Brn/tan showing 12 volts
Grounding sender singer wire pegs Guage at max temp, no fan engaged
Cutting and grounding Green white ECM wire, engages the fan manually

 

It is the CTS that gives the computer coolant temps ,the gauge sender has nothing to do with it

 

LMAO ok im the village idiot today. I was not aware that the there was a CTS sensor on the engine till you mentioned it, and after some digging I found it under the Throttle body. My brother built the engine about 10 years ago, and we finally got around to getting it running.

I found the sensor, and luckly the Parts store gave me the wrong sender earlier in the week, so Ill change it out when the engine cools down