The fan (high speed) is controlled by the temp switch by the thermostat, right? From what I can find it is supposed to be triggered at about 203 degrees F. Is this right? Does anybody have a source for switches with lower settings? The parts stores seem to only be able to look them up based on application and not temp.
I bought a new switch (Wells tu64) to experiment with. Put it in boiling water, and the switch didn't close. Has anyone been able to test these switches?
I don't think it works that way, I could always be wrong though. From my understanding the switch just sends the info to the ECM which then looks into the chip to see the on/off temps for low and high speed. With TL my high speed relay tends to kick in around 209°F. If you are having overheating problems you can just wire up a switch to the high speed relay so you can turn it on when you want to, that tends to help quite a bit. Also the high speed and low speed relays are the same so if your low goes out you can swap the high one in its place for temporary fixes anyway, the only difference is the low speed circuit sends the power through a big resistor located on the fan, this decreases the juice and slows the motor down. SO,
if you want a lower setting I believe you just need another chip or need a mod to your chip. Hope that helps and I didn't confuse you or spread any lies, I'm sure if I did somebody will correct me.
Maybe I was wrong, here's what Bruce Plecan said on the list:
I believe the *on* spec is 95-105dC.
It's the lowest one that I've seen spec'd from GM, they list the senders and
temps. in the Standard Brands Ign Catalog.
Hypertech and others sell a lower temp switch, thou.
I have the relays jumped so the ecm turns on the high fan. You could also
just jump the resistor at the rad fan, so as to have a high speed only set
up.
Bruce