C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Aux Rad Fan - On all the time????

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Old 08-06-2002, 07:14 PM
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WhiskeyPapa
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Default Aux Rad Fan - On all the time????

I just added a switch to manually ground the aux. cooling fan relay so I can turn it on when I please......any major drawbacks to letting it run all the time? :confused:
Old 08-06-2002, 07:43 PM
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65Z01
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Default Re: Aux Rad Fan - On all the time???? (WhiskeyPapa)

There's wear on the bearings and I've heard that less air flows at highway speeds with the fan running, but not sure of this latter one.

You could just install a new aux fan sw to bring the fan on at a lower temp.

I'm assuming that you wired your manual sw into the grn/wht wire so the fan shuts off when the key is off. Otherwise the potential drawback is battery drain if you should foreget it's on.
Old 08-06-2002, 07:56 PM
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WhiskeyPapa
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Default Re: Aux Rad Fan - On all the time???? (65Z01)

Yep...into the green & white wire...tested it to make sure it shut off w/ ignition.
And now that you mention it, the less airflow at highway speeds could be true, I know some airplanes use this principle to slow down on the runway (not actually reversing the prop, just spinning it w/ flat pitch) - anyway, could be true.
Anywhere w/ good instructions on installing the new temp switch?
Old 08-06-2002, 09:18 PM
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fixvet
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Default Re: Aux Rad Fan - On all the time???? (WhiskeyPapa)

I never run my override switch unless I'm in very slow traffic on a hot day.
You shouldn't need the fan turned on when cruisin' on the hiway. If you're still running hot at speed, you've got other problems. Probably clogged up radiator.
Good Luck,
:yesnod:
Old 08-07-2002, 12:19 PM
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dlmeyers
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Default Re: Aux Rad Fan - On all the time???? (fixvet)

At higher speeds, the ECM will cut off the fans and reduce the drag as air flows through the system. Reducing the drag will increase mileage and reduce wear on fan motors.

Darned engineers a pretty smart.

dlmeyers 90 coupe zf6 3 speed shocks

Old 08-07-2002, 12:40 PM
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65Z01
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Default Re: Aux Rad Fan - On all the time???? (WhiskeyPapa)

Since you have an aux fan you only need to drain about 1gal of coolant and replace your aux fan sw with a lower temp one.

I've done it and it's a piece of cake, unlike the guys who don't have the aux fan sw and have to remove a plug to install such a sw.
Old 08-07-2002, 01:08 PM
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scorp508
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I do not believe the auxilary fan is run at any speed over 30mph as it is more of a hindrance to air flow than a help at those speeds. I wouldn't want to have mine die prematurely from running it all the time.
Old 08-07-2002, 01:47 PM
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Ray Quayle
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Default Re: (scorp508)

I do not believe the auxilary fan is run at any speed over 30mph
Hey Scorp, How does that temp switch know it's going over 30? :lol:
Old 08-07-2002, 03:03 PM
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1986vert
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Default Re: Aux Rad Fan - On all the time???? (WhiskeyPapa)

Ever since I got my 84 both fans have been wired to run all the time when the car is running, is this causing it to run hotter at highway speeds as it cools down to under 200 on the highway on a really hot uper 90 degree day, and runs about 220 to 225 at the hottest in traffic even when sitting for a long time. Would I be better putting them on a switch or ???


[Modified by lee.anderson, 1:04 PM 8/7/2002]
Old 08-07-2002, 03:04 PM
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I do not believe the auxilary fan is run at any speed over 30mph
Hey Scorp, How does that temp switch know it's going over 30? :lol:
The ECM cuts power to the auxilary fan relay if it sees >30MPH from the vehicle speed sensor.
Old 08-07-2002, 03:26 PM
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vettmech
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Default Re: (scorp508)

If you have the fans hooked to a toggle switch the ecm won't turn the fans off no matter how fast the cars runs because you have overridden the ecm..........
The only drawback I have found to using the aux fan a lot is .......I burned mine up a couple days ago. I took it apart to see if I could fix anything in there and it's just burned up. Bearings are fine though and it's got 176 k on it
Old 08-07-2002, 03:30 PM
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If you have the fans hooked to a toggle switch the ecm won't turn the fans off no matter how fast the cars runs because you have overridden the ecm..........
Not true. I have a toggle switch hooked up to mine and when the switch is "off" the fans are ECM controlled. Only when I turn it on is the ECM overridden. The ECM turns the fans on by connecting the ground. The toggle switch applies a ground from a seperate location to power the fans. When the switch is off the original ECM controlled ground is back in action.
Old 08-07-2002, 03:58 PM
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Default Re: (scorp508)

If you have the fans hooked to a toggle switch the ecm won't turn the fans off no matter how fast the cars runs because you have overridden the ecm..........

Not true. I have a toggle switch hooked up to mine and when the switch is "off" the fans are ECM controlled. Only when I turn it on is the ECM overridden. The ECM turns the fans on by connecting the ground. The toggle switch applies a ground from a seperate location to power the fans. When the switch is off the original ECM controlled ground is back in action.
that sounds like a great idea.....would one assume that the green/white wire mentioned above just needs to see a ground and it wil override the ECM??? :confused:
Old 08-07-2002, 03:59 PM
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that sounds like a great idea.....would one assume that the green/white wire mentioned above just needs to see a ground and it wil override the ECM??? :confused:
Yes.

Frame --> Wire --> Switch --> Wire --> Relay terminal with Green/White wire.
Old 08-07-2002, 04:01 PM
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Default Re: (scorp508)

that sounds like a great idea.....would one assume that the green/white wire mentioned above just needs to see a ground and it wil override the ECM??? :confused:

Yes.

Frame --> Wire --> Switch --> Wire --> Relay terminal with Green/White wire.
:cheers: might have to try that in the near future!!!! traffic sucks here, but i am sure its not as bad as where you are scorp.....but i am sure it couldn't hurt!!!!
Old 08-07-2002, 04:07 PM
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Default Re: (scorp508)

Actually the aux fan relay is controlled only by the aux fan sw in the side of the block and the main fan only by the ECM.

I've wired my main fan relay (grn/wht wire) to the aux fan relay to bring both on around my 160 deg stat, using the aux fan sw to get the job done. So now the ECM can turn the main fan on when the A/C pressure rises too high but cannot turn it off if the aux fan sw is closed.

I found this much cheaper than a chip and less bother than a manual fan sw.
Old 08-07-2002, 04:10 PM
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Default Re: (85_togo)

I hooked mine up exactly like Scorp did, and it does shut off when the switch is off....also when the ignition is off, because the relay is still tripped by the same power source, you're just giving it a new way to ground when YOU want to.
I put a toggle switch under the dash just behind the diagnostic terminal....out of the way, and hard to bump, but not hard to reach. The pain in the butt was finding a place to ground the switch under the dash......
Old 08-07-2002, 04:11 PM
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The pain in the butt was finding a place to ground the switch under the dash......
There is a brace that runs at an angle sort of to the left of where my clutch pedal is. There was already a screw in it grounding something else, so I put it there.

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