More Dual Elec Fan Wiring Questions

[86Cutlass383SR]

I've read the electric fan wiring threads and have some more questions.

I'm going to be running the late 80's oem alum f-body radiator and the same dual electric fans. Aren't these fans single speed fans?

I'm also running a TPI based engine with the factory ecm but the aftermarket Howell wiring harness doesn't provide for the electric fans.

I have an add-on harness to run the dual fans but I'd like to improve the way they operate. You can run both fans with the temp sensor or 1 fan with the temp sensor and one fan hooked to the a/c compressor.

I'm no wiring guru so maybe these are dumb questions. If so, sorry. I still need these to work.

Should I try to hook these up the way the factory did thru the ecm even though the g-body a/c didn't use a press sensor?

How can I wire up one fan to come on normally with the temp sensor and the other fan come on with either/both the a/c is turned on or the engine temps raise to a higher temp than normal.

I'd like it all to work automatically and not have to flip any switches for override.

Would it be better to run them seperately as described above or just have both fans come on at the same time?

I'm installing a new engine and I'm setting it all up for the first time so I have no past dealings with this setup. What's the best way to wire it all up?

[H2Ogbodies]

My advice is clean and simple. Go with a Mark VIII fan, use a temp switch which would serve to ground a 70-amp rated relay to trigger the fan. With a bit of creativity, you could also use another relay that completes the ground circuit once the AC is on whihc could run in parallel with your ground circuit for the temp switch-that way the temp or the AC activation will trigger the fan to come on full speed. You want the most amount of airflow possible pulling heat out of the condensor with the AC running-that is where the Mark VIII fan literally blows away every other fan! Plus, you have the room for one!

[86Cutlass383SR]

That may be a good option. Thanks for the idea.

[BigBlockOlds]

I've always just had my dual fans come on at the same time and at full speed.

With my F-body LT1 fan setup I used a Perma-cool adjustable thermostat kit and a 30A relay for the second fan. Wired it according to their diagram and it always worked just fine.

I essentially have the same thing now with my dual Derale fan setup but everything is controlled through the EFI ECU instead of a separate temp sensor.

[MonzaRacer]

2 good fans, one wired to temp switch, one wired to ac in falling circuit so both are powered if ac is on and an over temp switch to be backup.
I have some pics of fans i have used with great success if I can find disc again.
I tend to dig up salvage yard fans when cheape enough. My big block 70 Monte Carlo had a single from a basically a 90s Cavalier and ran perfectly cool on a 3 row radiator and high compression so , it doesnt take big bucks just a little research and ask enough questions. unless you want to spend big dollars.
My last 3 electric setups had less than $75 each in.

[MonzaRacer]

OK so first of all I have seen plenty of the Mk-VIII setups lock up, they cost a lot and as for packaging if it fits ok but what if it doesnt?
I have had 3 people have those go bad, one was salvage yard unit, ok it may have been bad from get go, the new aftermarket was on a $680 Ron Davis rad I believe and the rad is getting repaired at great expense of sending it back, repair and shipping back,,,and his car is down, and then a true Ford/Motorcraft unit that lockedup a motor 3 weeks out of warranty.
And besides for me I like to try different things.
Last car I had the free hanging(no shroud) GM fans installed on, customers car not mine, the car went from some odd looking dual fan knock off with shroud, to the ones I installed, the car gained about an inch of room if not more, the guy could actually do some things underhood after and the guard was simple piece of plastic he picked up and trimmed from salvage yard.
Dont get me wrong if the MK-VIII is for you run it, but after doing my first few cheap and they worked, I am sold on some different , cheaper options.
Just keep it cool!