OK like many I don't like sitting in dead traffic in the middle of a hot summer day with the rad air dam doin bupkis staring at this (both fans verified running at this point BTW so at least the stock system is working to spec..) Granted the gauge may be overstating but just the same.



So I compiled some great data from past threads as below.

My question though - with regard to the bolded - I think a "mild" fan switch..uh, switch to SW505 would not necessitate or really benefit from a 180 thermo?

Stuff like this (and possibly associated thermo) seems cool

https://www.tpis.com/parts/view/191

but at the end of the day it appears the simple $12 delco may do the trick. Basically »both« fans running by ~215F should be better than the second coming on once you're already cooking at 238F. At the same rate I kinda don't need'em both running (stock afterall) once I've reestablished airflow when moving again at good speed. Lots of traffic tho so maybe I need more.. *apologies in advance for all the celsius conversions..this damn country. Thanks!

....
-> New Fan Switch? New Thermostat?
Stock 220/222 (104/106C) first fan (d-side) via ECM (via CTS) then 238 (114C) secondary fan (p-side) via thermostatic fan switch
Hawks on 185 (85C) off 165 (74C) ...w pigtail?
SW555 on 204 (96C)
SW505 on 213 (101C) off 185? ACDelco D1855B
SW500 on 224 (106.7C)
SW502 on 229 (109C) (stock)
Off spread usually 15F or 20F

In '89, the A/C would cause both fans to run.

I have a 200(93C)/185(85C) fan switch on the passenger side. At the moment, I have the stock GM chip in the car. Now in this situation, you would think that the passenger fan would come on before the ECM controlled driver side fan. But they both turn on at 200° (93C) So it appears that the passenger won't come on without kicking on the driver side if it's not already on.

(a/c doesn't turn on second fan for a guy) =your engine needs a certain temperature before the addition of the A/C can create sufficient pressure for the switch to close.

Stock thermostat 195(91C) fully open between 215(102C)- 225(107C)

Thermostats aren't 100% precise. You'd want a shut off temp at least 10-15° above your t-stat temp, if you want you fan to cycle on/off.

Run a 180. You lose power and increase wear running colder. Best temp for wear and power 190(88C)-200(93C). Run this temp with closed cold air system you will be fine. Nascar runs these temps research it. Oil needs to be 300°to properly lubricate. Early on fan switches and cool thermostats just fool the ecm into throwing more timing at the motor, thats where people are fooled. Motors are designed to run these temps for complete combustion and wear characteristics. Stay away from fancy units