Hi,so far i think it's just question time,i recently noticed the temp. gauge started reading above 220 on way to work,cracked in driver side end cap,had repaired,running @ 50/50 mix,on test run to look for leaks,lower radaiator clamp needing some tighting,the thermostat opens just past 220 on gauge,then drops to half way between the mid mark and 220 while moving,pull into driveway and watch it slowly climb above 220,turn on AC,both fans start running,with AC off,neither fan runs,do i replace the semsor on passenger side between 6&8,or the one at the bottom of block,i want to also have a toggle inside car to control the fans,since there does not seem to be a more serious problems other than the fans not coming on without the AC on,when i search tech,it said to unplug the upper(6&8)splice into it and ground other side of switch,sorry for long read,just curious,Thanx,charlie

 

Charlie,

If you have the LB9, the CTS that signals the ECM is located in the front coolant crossover of the intake manifold. The ECM depends on this signal to determine engine coolant temperature. When the ECM is told that the coolant is 233° or above, the ECM will turn on the electric fan(s).

If the CTS is reporting incorrectly, the fans may not come on until the coolant is a LOT hotter than that. Make sure the CTS is producing the correct resistance at a given temperature.



Instead of a toggle switch, you might want to check out an adjustable fan control switch that mounts to the radiator (about $40 complete).

You'll find your CTS here: