Wiring question - Taurus fan and Holley controller

OK, so I have the Taurus fan setup, its a single fan with a low and high fan setting. However, from what I have read, if you have the low and the high on at the same time it creates a medium setting instead of the high setting. I am looking to see if my wiring diagram is correct. The Holley EFI ECU can control the fans with negative cut off. This is what I came up with, the idea is that the third relay will ultimately turn off the first(low) relay when the second (high) turns on.




let me know.

ok, I got to thinking and added to it, its a bit neater now.  I added fuel and water pump control as well as an override so I can power the low speed of the fan and the water pump when the car is off.

thoughts?

OMG - Instant headache !!! I'm gonna' have to look this over again when I've got a few minutes and a fresh drink next to me !

I also just noticed that two wires look like they are connected but aren't supposed to be, I have to update it

ok, fixed it. Thanks for looking at it John. I think its pretty spot on but I'm not 100%

In the case of an accessory that requires significant voltage ( fans ) use real heavy gauge wiring on the IN and OUT circuits,... not so important with many other lower voltage accessories like fog lights, fuel pump, etc......

30 =  Hot At All TIMES
87 = Hot OUT
86 = "switched" Ignition power
85 = "switched" negative 'signal' wire to activate relay.



OR:  

30 =  Hot At All TIMES
87 = Hot OUT
86 = full time ground
85 =  "switched" positive 'signal' wire to activate relay.




I would break this entire set-up into smaller parts.  Looks like the ECU sends a switched power for the water & fuel pump relays & you said the ECU is sending a switched ground to CUT OFF the relays:  IS that right ??

I'd add a few more fuses...... give each fan relay it's own ( 30 AMP ) fuse so if there's a problem with 1 it doesn't kill the entire fan system.

I would wire the fuel pump and the water pump just like the picture of the fuel pump relay above.... each pump with it's own dedicated full-time ground, each relay with a separate ground with the switched power from the ECU turning both of them ON at START/RUN.  ( 87 from each relay to power side of it's pump motor )

Not sure why a 3rd relay is needed for the water pump...... you can simply tap/splice the manual switched ground wire into the switched ground wire on it's primary relay switched ground terminal wire and eliminate the 3rd relay entirely.


I didn't get to look to hard at the fan wiring specifically;  I kept getting a bit lost and now I'm out of time and need to go !

Yes, the ECU sends a ground signal to the relays for the fans, correct

Good point on the separate fuse per relay, the high requires a 60 amp fuse as it can pull that at start up but figured that it would be safe to combine if I was shutting one off while the other is turning on, but good point, I will do that. The 3rd relay for the water pump was so that I could over ride the lack of power to the pump and power the relay with the same manual ground switch as the low speed on the fan. so it will run when the car is off.

I heard, didn't test it, that its not good to have both leads powered at the same time on the fan because instead of a low and hi it would become low and medium. I want the Holley EFI to control both fan speeds so I figured I would need at least 3 relays for that, one to power the low, one to power the high, and one to turn off the low when the high is on.

I'm also using 70amp relays for the fan so there shouldn't be an issue.