Need help from the electrical gurus on the board

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08-12-2007, 03:53 PM
Titus

Need help from the electrical gurus on the board

Many FI Miata owners wire their fans in parallel to improve cooling. The LINK ECU that I have provides a feature that will allow me to do things a little different. There is a terminal on the LINK that will go to ground when the temperature of the coolant rises higher than the point I program into the LINK. FM recommends leaving the cooling fan to be controlled by the temperature sensor on top of the thermostat, and then using the ECU to control the A/C fan via the terminal that goes to ground. This allows you to stage the fans so they come on a different temperatures.

I like this idea, but want to take things a step further. I would like to wire things so that the A/C fan will be turned on by the ECU at the set temp, but I would still like it to come on if the A/C is turned on while the ECU temp has not been met. I am thinking I need a second relay, perhaps in parallel to the stock A/C relay, but I am obviously already in over my head. In my search for someone else that may have already done this, I came across THIS wiring diagram that shows the A/C fan relay circuit (bottom right corner of page 5). I know it probably gives me enough information to figure out what i need to do, but I don't remember enough from my electronics classes in school to put 2 and 2 together. Can anyone help?
08-12-2007, 03:55 PM
tailchaser

My advice for dealing with electrical issues starts and ends with submersing it and looking for bubbles.
08-12-2007, 03:57 PM
Titus

Quote:

Originally Posted by tailchaser

My advice for dealing with electrical issues starts and ends with submersing it and looking for bubbles.

You've been spending too much time with Bean. :rolleyes:
08-12-2007, 03:59 PM
POS Racing

Quote:

Originally Posted by tailchaser

My advice for dealing with electrical issues starts and ends with submersing it and looking for bubbles.

:clap:
08-12-2007, 04:36 PM
HudsonHawk

One relay with 2 ground paths. One path to the Link the other to the switch that controls the ac compressor. So if either or both are grounded the A/C fan comes on.

EDIT: never mind the ac does no work on a grounded basis. It is controlled via a switched circuit on the ECU.

And based on the schematic you attached it would require a bit of additional wiring to just turn on the AC fan and not the compressor clutch.
08-12-2007, 05:59 PM
Treibenschnell

Quote:

Originally Posted by Titus

You've been spending too much time with Bean. :rolleyes:

And this is a bad thing? :rolleyes:
08-12-2007, 06:09 PM
Titus

Quote:

Originally Posted by Treibenschnell

And this is a bad thing? :rolleyes:

Only when we are talking about Miata wiring. ;)
08-12-2007, 06:14 PM
Treibenschnell

Quote:

Originally Posted by Titus

Only when we are talking about Miata wiring. ;)

Or windshields... :D
08-12-2007, 06:17 PM
Titus

::Rain::
08-12-2007, 08:04 PM
Radio-Active

Bean has got an excellent schematic laying in a box though. :D

I used it to find his starter issue.
08-13-2007, 09:47 PM
TurboDuane

What ever you do you definately don't want both fans coming on together, as it will just about kill the car when they come on. At least it did on my '90 when both SPAL's came on at the same time.
08-13-2007, 09:54 PM
johnwag

Quote:

Originally Posted by TurboDuane

What ever you do you definately don't want both fans coming on together, as it will just about kill the car when they come on. At least it did on my '90 when both SPAL's came on at the same time.

I run the parallel fan mod and I have the stock radiator fans on my '96. I've never had any cooling issues or fan failure.

Do the SPAL's require more electricity due to the their higher speeds?
08-14-2007, 07:24 PM
TurboDuane

Quote:

Originally Posted by johnwag

I run the parallel fan mod and I have the stock radiator fans on my '96. I've never had any cooling issues or fan failure.

Do the SPAL's require more electricity due to the their higher speeds?

Yea, they pull a lot more amps. When they both come on together, the drain on the alt. would just about kill the car, just before the car would kick in a little extra power to compensate. But if it happend at just the right time, it would kill the car.