legacycentral bbs

ok...i'm not too great when it comes to electronics... I have a cooling fan question...I picked up a used MAIN FAN from the junkyard today... this might be a good one for vrg3...

If my assumptions are correct, there are two positive (+) and one negative (-) wire for each cooling fan...

I have the stock driver's side fan (3-wires) that i got from the junkyard hooked up as the MAIN FAN, and i have an aftermarket (2-wire) fan hooked up as the SUB FAN...

When hooking up the aftermarket fan, i hooked up the black negative (-) wire and the green positive (+) wire, leaving the last blue positive (+) wire disconnected.

With the above setup, the MAIN FAN always runs in ACC and ON...and...
the SUB fan always runs when the key is in the ON position
(pressing the AC button doesn't have any effect on the fans)

The setup i had before i picked up the new MAIN FAN today worked with two aftermarket fans with 2-wires...

With this setup, the MAIN FAN would run at all times in ACC and ON...and...
the SUB FAN would only run while the key was in the ON position and the AC on like it is supposed to.
This setup worked fairly well for me, even though the MAIN FAN was always on when its not supposed to be.....but since i got my hands on a stock MAIN FAN, i decided to put it in.

would a setup with a stock fan and an aftermarket 2-wire one cause any electrical changes that would cause them to run all the time?

maybe the wiring diagram could tell someone who actually knows how to read them...i've tried, but i don't see it....

The only thing that i could think of that would cause both fans to run all the time would be a faulty coolant temp sensor; but both a "D-check" and a "read memory" came up with no codes, and the resistance of the sensor is fine...

sorry for being so complex, i hope someone will be able to explain it to me.

Andrew

One question before a big response. Aren't the fans (and other items around the car) switch through the GROUND and not through positive? Meaning they always have positive power?

Each stock fan does have two positive wires. I don't quite understand why or what they do though. It may be that it's possible to run the fan at half speed by powering only one of the positive terminals.

In any case, the main fan is supposed to be powered through the main fan relay, which is controlled by the ECU. This relay is ground-switched. The fans themselves are grounded to the chassis and are positive-switched. One of the main fan's positive connections goes straight to the relay and the other goes through the "short connector" to the relay. I don't know what the short connector is; it appears to be just a 2-pin connector the rear of the driver side fender that you can remove as a diagnostic aid or somesuch.

The sub fan appears to have one of its positive lines powered through the A/C sub fan relay and the other through the water temp sub fan relay. The former appears to be tripped by the voltage that drives the main fan. The latter is controlled by the ECU.

This is all based on just a quick look at the wiring diagram, so I may have gotten some of it wrong. But... I don't see why you'd ever see the main fan rnuning at all times. Maybe it'd be worth checking out the relays. I suppose if your aftermarket fan drew way too much current it could have damaged a relay to the point that it's stuck closed or something.

ok... i did some experiments today

I had two other aftermarket 2-wire fans that i used as guinea pigs while the two i have on the car now could stay...
I had easy access to the wires and i started connecting different wires to others and noted what happened.

WITH THE IGNITION SWITCH IN THE ACC POSITION:
On the main fan side, the YELLOW/RED wire is live while the LT GREEN/BLACK wire is dead.

On the SUB FAN side, the WHITE/BLUE wire is dead while the YELLOW/GREEN wire only becomes live when the YELLOW/RED and LT GREEN/BLACK wires are touched on the MAIN FAN side.

WITH THE IGNITION SWITCH IN THE ON POSITION:
AC OFF:
On the MAIN FAN side, the YELLOW/RED wire is live and the LT GREEN/BLACK wire is dead

On the SUB FAN side, the WHITE/BLUE wire is live while the YELLOW/GREEN wire is dead.

AC ON:
On both sides, all wires are live

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This would explain a few things, such as why the MAIN FAN was always on, for example

BUT, are the wires supposed to be this way?

Maybe someone can make sense of this...

Thanks so far!
Andrew