That is close enough. My fan comes on at 206° and turns off at 195°. I use a 180° thermostat.



Even if the fan doesn't run constantly, it will run more than necessary. With my 206°/195° on/off temps, my fan only runs at very low speeds. There is no need to waste gasoline and wear out a fan motor trying to keep the engine at a temp range it constantly resists.

RACE ON!!!

 

do u know the spread on a typical GM fan switch? I think it is 16 degrees, but never saw it documented.

Even the 89 shop manuals are full of typo's. the temps are listed in C, and some of the conversions to F are just wrong. This is in the F-body manual I have for 1989.

 

I don't know of there is a typical, or standard "On" to "Off" temp spread. When I bought my switch, i selected it from a catalog of stock switches. I looked up the stock switch, then in the numerical listing, in the back of the book, I checked the specs for the stock switch. Finally, I went through the numerical listing looking for specs that matched the stock switch, especially the connector, with a temp setting I could live with. I don't recall both the on and off temps being listed. All I remember seeing is the "On" temp.

RACE ON!!!

 

I feel the off temp is equally as important. I don't want to fans running when I'm crusing down the highway.

On the 89 ECM, when the AUX switch closes, doesn't that feed back to the ECM to kick on the primary fan ?

 

Absolutely, but with my 195° off setting, that isn't going to happen. I agree the "Off" temp is important. That is what I was talking about a few posts back. If the "Off is too low, the fan will never shut off, once it's triggered. I have a manual switch with three positions. Stock operation, forced on, and can't run, regardless, off.



Not with the stock wiring. But in most cases it wouldn't matter, anyhow, because the main fan is (should be) on when the aux fan kicks in. In the 1985 - 1989 cars with two fans, the fans are independent of one another.

BTW, my '84 has no aux fan (wasn't available) and the main (only) fan is controlled by a thermo switch in the head like the aux fan in the 1985 - 1989 cars. On my car the ECM has nothing to do with the fan.

RACE ON!!!