I want to add a lower temp fan switch to my 3.1 to lower that ridiculous 230* fan turn on. Napa has the same part numbers for the 2.8 and 3.1 heads, so I assume they are the same, and the fan switch hole is plugged on mine.

Has anyone done this before, or know how the plug comes out? I haven't looked very closely, but there doesn't seem to be a lot of room. Are you 2.8 guys able to change the switch without too much trouble? Thanks

 

The 3.1 fan is controlled by the ecm. The 2.8 is controlled by the sensor in the head.

If you want to have the fans come on early, just wire in an over ride switch. Its fairly easy.

 

so is it the one in the Pass side head or the Driver side head?

 

I'm going to have to look into this a bit more, there is conflicting info on what that sensor in the rear head is for.
Some say it's to conrtol the fan (switch), others say it's for the gauge, and the fan is controlled by the ECM.

 

looking at my Chiltons manual there is no other connection to the Fan relay other than the ECU control. the only other connection i can find that refers to a fan is a Fan Pressure switch which from what i have found is the AC switch to tell the ECU when the AC is active.
which leads me to ask why will my fan run non stop if i have the AC pressure switch unpluged and why does it not run if i plug it back in? i have let the temp go to about 230* before i shut it down and unpluged that switch so that the fan would turn on and restarted the engine so that it would cool down. Its an aftermarket gauge. my father and i checked the CTS and is working properly. Does anyone know what the Temp/voltage values for the CTS are? if i knew that i could check if the CTS and the gauge are reading the same.

Just checked with Oreillys and GMparts direct and both show a fan switch.

 

Left head, up front is for the gauge in the dash. Both 2.8 and 3.1


Right head, rear, is for the fan on a 2.8. This hole is plugged on a 3.1.


3.1 fan sensor is the same as the ECT in the top front of the intake. This can not be changed because it also tells the ECM what the coolent temp is.

You want your engine to run cooler on a 3.1, heres your options...
1. 185 t-stat
2. over ride toggle switch
3. custom prom chip
4. install a whole new ecm system for the fan alone.
5. Install dual v8 fans

I have 1,2,5 on my car, and whenever I get a custom prom, thats getting changed too.

 

I dont care about it running cooler i just want it to turn the fan on properly so that the car will not take 15mins to get up to temp and i wold like to stay away from a manual switch cause i have family members that drive the car also.

 

I just went out and checked and my car does not have a sensor in the Pass side head it has a plug and the CTS only has 2 wires not three. heck i could not even find a wire back by the head that might plug into a sensor there. if i removed the bracket holding the coil and such would i have the room needed to remove that plug and install a fan switch there?

 

My understanding of the way the 2.8 fan switch works is it grounds the fan relay.

I know on the 3.1 the ecm grounds the relay, but I have an override switch connected to the relay ground wire. What I want to do is have the 2.8 style fan switch ground the relay so I don't have to do it manually.

 

im looking in tunerpro, and the 2.8 ecm has "Fan, minimum to enable(coolant temp.) = 106.25 *C, so it looks to me like the ecm controls the fan(there are a few other things about the fan too, run time, vehicle speed, etc).

 

so thats 223.25 right? well what value should that showup as in Volts for the ecu? i want to check that my CTS and gauge are reading the same cause i have let the car go to 230* on the gauge and it wont turn on. i know the ECU is working cause if i have the pressure switch unpluged it defaults to on but if i plug it in it wont turn on at all even when my gauge is reading 230*. could there be that much difference in temp between the CTS and the sensor in the head?