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adding manual fan control

Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Ok, I'm buying the parts I need to manually control the auxiliary fan I'm installing. What I'm hoping to do is run a wire from the battery + side to a switch under the dash and out to the + side of the fan motor, and another wire from the - battery side to the - fan side. I want to have the fan work even when the engine is off, and I'd prefer not to have to take the dash apart to run off an always-hot circuit in the fusebox. Is there a better place to tie the wires to? I know some people have done this mod; how do you all work it?

Thanks...
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Top

Well-known member
Joined
Mar 20, 2002
Messages
161
Location
Las Vegas, Nv
Corvette
1986 Convertible Dark Red Metallic
If you wire it like you said......+ side of battery to the switch and then out to the fan you don't need anything else. With the switch 'open' i. e. 'off' the fan will get no power. As soon as you 'close', i.e. turn on the switch you will be running the fan direct off the battery. You need to add a fuse, 10 amp should do the trick, between the battery and switch though. The fan should already be grounded. I would be surprised if you need a direct ground from the battery. You just need to get power to the fan. If you do need to ground it keep it as short as possible and ground to one of the grounds by the fan. Hope that helps!! :bu
 
E

Eagle85C4

Guest
Actually it would be easier to wire directly to the relay's and it would be better to wire it off the accessories so power can be switched. You would not want to leave the car with the fans on and come back to a dead battery
 

69MyWay

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Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Eagle85C4 is exactly right. Adding a relay is rather simple, and kind of fun.

First, you need to get a simple cooling fan relay from the auto parts store for say, oh, really almost anything. It is best if you choose a really common car like a 92 Buick Century. That should cost about $7. Now, go to the junk yard, find a 92 or equivalent car and snip out the fan relay harness where it plugs in. Go ahead and get two or three of them and some extra relays.

Now, back at your house, use a 8 or 10 gauge wire. Go from the battery, or 12+ terminal on the starter to about a 25 amp fuse. You can make a fuse real easy by clipping the wire in two. Crimping a female spade terminal to each end, then plugging the fuse into the female spade terminals. Wrap some electric tape around the bottom, and you got it.

Now, go to the hot side of the relay with that wire. Come out of the relay on the other hot fan side and run that to the fan 12+ and take the wire out of the fan to ground on the chassis.

Now, find a good 12+ ignition only powered wire. Run that to the coil part of the relay. Run the other side to ground. What this will do is make the pusher fan run all the time when the key is on. Or, you could take the ground side of the coil, run it into the car to the switch, then the otherside of the switch to ground. This way you choose when you want the fan to run by clicking the switch, which will close the ground circuit, which will close the coil, which will connect the main power to the fan. This will only happen when the key is on, thus you can't run your battery dead by forgetting to turn it off.

Of course, you use the junkyard terminal connector end to put a fresh factory look to the relay, and mount the relay where it is easy to get to. I suggest behind the battery on the firewall.


Good luck!
 
B

boblx2a

Guest
Okay, I'll give this a go since there are many ways to do what you are trying to do. I have recently done something similar on my '85.
If you have two fans there are two relays. One is obvious it is on the left front fender well, the other is behind the battery in that little cavity toward the driver's door.
If you unfasten the relay on the fender and hold it up in front of you there will be three wires on the right, then a space, then a single wire on the left. The two wires in the middle are the ones that control the relay. You can measure +12V on either of them when the relay is not energized. The leftmost wire of those two middle wires is where your temp sensor applies ground. When this wire is grounded the fan comes on. Go ahead and try it you will see what is needed. The right wire of these two middle wires has +12V on it continurally. All you need to do is splice a wire (or remove that one and replace it) to this pin that sends it a ground signal. Finding the ground under the dash may challenge you but you can find one. You can do this to both relays or either of them. Then with a double pole, single throw switch fastened to the dash you can control either or both of the fans. You won't have to worry about the fans staying on when you turn off the ignition and you won't have to locate a +12V source.
 
Joined
Apr 18, 2002
Messages
1,441
Location
Staten Island, NY
Corvette
1999 Torch Red Coupe
rrubel

most american cars like the vette only switch the ground on and off to the fan, the motor always may be getting power or the "hot" side. For my 95 all i had to do was mount a switch in the car and solder an eylet to a wire, screw that wire to a metal ground and connect the other end of the wire to the switch, the run a wire frrom the other pole on the switch to the ground wire on the existing relay, if you are adding a fan just tap the hot side of the existing relay and connect the switched ground to the new fan.
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Welp... the car currently only HAS one fan... which is why I'm adding the pusher. No second relay, no temp sensor, no ground wire, etc. Reason why I want it not connected to the ignition is for when I take the car to the track or strip - with the engine on, it's producing more heat and I want it to cool as quickly and as far as possible, and I may not always be with the car (so I can't leave the key in the ignition).

69myway, your approach looks the most doable, but curious - why 8-gauge wire? Electronics store said no bigger than 16, no smaller than 20. Hm. The wire from the fan itself looks to be about 16 gauge.

Time to hit the parts store again...
thanks for all the help!
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69MyWay

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Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
I forget that this is a smaller fan motor, but 10 gauge would be just perfect. You can't go wrong with that size on this application.

Let me know if you need any more ideas. I can also tell you that the G.M. dealer can sell you just the pig tail wire harness end that plugs into the relay. My favorite one like this is the one that fits the 90 Corvette fan relay and the 90 corvette fan relay. It is a high quality unit with a nice weather pack seal. The relay pig tail is about 5-$10, and it makes a awesome professional factory finish.
 
Joined
Apr 18, 2002
Messages
1,441
Location
Staten Island, NY
Corvette
1999 Torch Red Coupe
If you check the chiltons manual you can see the relay always has power even with the engine off and key out. So you can run the fan anytime (I do the same thing waiting in the staging lanes) and if you tap the factory relay you can use almost any guage wire as you are only switching the ground to activate the realy for the existing,

whatever "system" you use good luck, it gained me 2 tenths having the coolent temp where I want it.
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
69MyWay, what dealer do YOU go to? I happened to stop at my local one yesterday and was quoted $60 for the harness from the auxiliary fan to the relay. Maybe the standard fan's harness is cheaper.

Looks like I'll be doing more research... I'm also having difficulty finding a place to sell me those weatherpack plugs - none of the local auto parts stores have them, the dealer doesn't have them, and I've only found one place online that sells in quantity less than 500...

I need a Pick-n-Pay around here :(. Our local junkyards rarely let you peruse the merchandise.

Anyway, enough whining on my part. Time to go plan. With a three-day weekend coming up, I should be able to get it done provided I have all the parts.

And Warren, I can easily believe the 2/10ths part. My runs last week got steadily slower by about that much as the car got warmer.
Thanks again.

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69MyWay

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Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
I happen to have one of the best G.M. parts guys around that helps with my G.M. parts.

There are an aweful lot of dopes working behind the dealer counters. They sell replacement/repair harness connectors for fan relays. Too bad you are doing this this weekend, because I could dig some part numbers up for you by next week.

On the flip side though, that is why I suggested the Junk Yard, so you get it all at once.

The $60 sounds like the actual factory wires harness, and you don't really need that.

If you are not in a big big hurry, and can't find it local, I should have a harness laying around here and would be happy to snip and mail it to you for the cost of shipping (maybe $5 or so). Just send my your address

chrisnikki@juno.com
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Chris, if you can just supply the part numbers for those things, that would be great. I have some other stuff I can work on this weekend instead, and can do the fan next weekend.
Thanks...
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Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
One final question - for those of you who have the auxiliary pusher fan, how are the wires to the motor routed? I found the removeable grommet to run them into the engine bay, but can't find the holes to attach the wire clips to (there are two clips on the wiring harness, one maybe 6" from the motor and the other 12" from the motor. I found a hole on the front diffuser, but nothing for the second clip. Other than this, the fan itself is physically mounted. 69MyWay, I got a fan relay from a 90 Vette and I'll run the various wires to that. As soon as my weatherpack plugs arrive, I should be set. I'll have all the wires run this afternoon and just be waiting for the plugs.
Thanks...
[RICHR]
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Ok, last question, I promise... How the heck do I get through the firewall? I found the thick mass of wires that starts by the clutch pedal and comes out by the battery, but darned if I can get anything in there. Found where the hood release cable runs through, but don't want to mess with that. Any other suggestions? I have a brake booster staring me in the face with not a lot of room to manoever around it.

On a better note, I ran some test leads to the fan and it does actually run... and doesn't vibrate so it's in tight. Found a nice ground spot right behind the radiator that I can run the motor's ground wire to, and found a good path for the hot wire, and a decent place to mount the relay, plus where all the hot wires are connected to (behind/below the battery). I think I have everything figured out in my mind; it's just getting the switch connected that's the sticker now.
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Top

Well-known member
Joined
Mar 20, 2002
Messages
161
Location
Las Vegas, Nv
Corvette
1986 Convertible Dark Red Metallic
I went throught the hood release boot or grommet. Just poked a hole right in it with a coat hanger, then bent the end and pulled the wires though. After I hooked up everything and tested it all I went back to the grommet and sealed both sides with aquarium silicone. My .02 cents. :J :bu
 

69MyWay

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Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
I don't have the g.m. part number handy for the repair weather pack harness kit.

Here is what I did do. I created a thread with photos here:

Relay Thread


I hope it will help clear up questions about relays, how to put them together, and the value of junk yard scrounging to get a nice weather pack harness terminal.
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Thanks, that's an *extremely* useful thread. And your animal assistants were helpful :).

Soon as I line up the rest of my parts, I'll be set.

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Joined
Oct 30, 2001
Messages
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Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Top, I followed your lead and went through the hood release grommet. Couldn't find a verifiable ground in the cabin, so I ran two wires through - one to the relay, one to ground, meeting at the switch. Tomorrow I hope to hit a junkyard and get the relay harness. Now to figure where to mount the switch... Had the perfect place in mind, below the fog light switch, but there's HVAC all through there.
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Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Ok, fan is done. Yay! :) :beer

Did make one snafu - forgot about the rotating headlights. Left-side light comes around, snags my wiring, rips it out of the harness. Bad thing. Wound up relocating the relay to by the alternator (it was up front near the vacuum cannonball) and tie-wrapping the wires to the fan itself to the middle of the radiator. The switch is located behind the ALDL connector; it's out of the way (won't hit it by accident) and invisible.

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