ok here the promblem...


Monte carlo 3.1 v6 ls


It was heating up ... the guages went all the way to 260...

Then the fan on the passenger side turned on..

I went ahead and checked the thermostat.. it was reeeeallly stuck.. so i installed a new one.. Now i do feel the water flowing thorugh the return hose. My promblem is that the a/c turns on by itself when the needle reaches a little past the middle point.. The other does not.. The needle got to between half and 260 and the other fan never turned on. I went to a auto part store and they told me they have a fan sensor switch which they tell the fan to trun on. One fan does turn on (a/c) the other does not. When the temp went to 260... the passenger fan did turn on.. But when it hit 260... so the fan does work..


any one heard of these sensors and where they located... also..
Any answers of what else can be causing it... ?

please help me...

I am having the same troubles. my car has never gotten to 260, but when it gets warm the primary fan doesn't come on.

the fan switch is located in the intake manifold near the t-stat housing. When you replaced the t-stat, did you bleed the system? IF not, you could have air trapped in the system, which will cause the fans to not come on due to lack of coolant contact with the switch. Since your problem started before the t-stat swap, I would replace both the primary fan relay, and the coolant temp sensor/fan switch. They areboth under $15-$20 each, and either could cause the fan to not kick on.

does the coolant sensor (that goes to ecm) allow the ecm to do many other things, like control fuel/air mixture on startup depending on temp. etc?