Ok I have a taurus fan,I know it is 2 speeds,i will wire in 2 relays.I want the fan to come on at 200 off at 185.I don't want manuel control.what I want to know is what determines when the hi and low speeds come on?Should I just wire hi speed only? Looks like when it gets to 200 the hi speed should come,if so,why should i wire the low speed.Also are the temps ok?

Those temps look fine to me. If it's reasonably quiet, you might want to have it run on low all the time and switch to high at 200F. The Taurus probably had two temp thresholds.

Thanks Toofast,I was thinking maybe the low speed would be all I needed.I think I can do one or the other.Anyone running just the low speed,if so does it cool ok?

I have the same fan, had the 408 big block in last summer with an aluminum radiator, no problems just running on low. I thought I would have to hook up the high speed but haven't needed it, ran 180 to 190 with a 180 thermostat, even with outside temps 100+. :beers:

Thanks Tim,I think I'll just hook up the low speed first.

If you have the fan I'm thinking of, you must drop the voltage to the low side when you go to high. Feed the low fan through the NC side of the high relay

If you have the fan I'm thinking of, you must drop the voltage to the low side when you go to high. Feed the low fan through the NC side of the high relay

that took me a minute to figure out
but I think you are saying that we should not power both the high and low speeds at the same time?

Sorry to sound dumb,but what is the nc side?Thought I had this fig.out.

NC = normally closed, NO = normally open. Most auto relays have a Form C setup.

http://en.wikipedia.org/wiki/Relay