Water Cooled Question, Fan sequencing / works great! Options

[76-914]

For my Suby 6 conversion I've installed a twin fan system (from a Dodge) on my radiator. One is single speed (3 wire) and the other is 2 speed (4 wire). Which one of these 2 fans comes on first? Do they both run at times? Will I use the 2nd speed of the 2 speed motor?

[Tom]

Kent,
It looks like both pins 33 and 42 would need to be grounded at the point where high speed is needed. You understand the low speed circuit correctly. It is acting like a voltage divider circuit. Each fan has the same resistance, therefore the same value of circuit voltage is dropped across each one, in this case 6v, or half speed for each fan.
I would guess that pins 33 and 42 are controlled by an input from separate temp sensor inputs into the ECU. One temp sensor would close at say 195 degrees and cause the two fans to operate at slow speed, when the temp increased, the other sensor closes, causing the high speed circuit to work. The first temp sensor will still indicate closed until the temp lowers enough for the second sensor to open and then the first one to open as the temp falls even lower.
Tom