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Discussion Starter #1
I have a rear defroster fan i got somewhere, probably on ebay. It is the fan only and did not come with a switch or wiring. The fan has 2 wires coming off it.

Can i get any type of ON-Off-ON switch for this or do i have to get a resistor switch? i heard some fans on some cars had the resisitors built in and all that is needed is an ON-OFF-ON switch and the fans internal resistor does the work of slowing the fan. Please advise. If you need more info on the fan I can get that. Also, If I do need a resistor switch, does anyone have any suggestions that they may have used that might help me. THANKS

FYI, I believe the fan might by out of a 70's style camaro because the grill is plastic not metal and the grill vents move in 3 directions, Not just 2 light some I have seen.

Once again, Thanks for the help on this.
 

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Discussion Starter #2
Anyone?

Once again just trying to find out if I can use any type of switch for the rear defroster fan?

Don't need original style. Please advise.

I looked at some other older posts but did not really find my answer there. Thanks.
 

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You need to look close at the fan motor wires and see if maybe if one of the two wires need to be grounded.

On my Nova rear defrosters there are two wires coming off of the motor:

http://rides.webshots.com/photo/2554426200060464735ZIOzed

The black one with the ring terminal goes to ground and the violet one to the indash switch. On this design the violet wire needs to get full voltage (12 volts or so) and the fan will then spin as fast as it can. When the indash switch is put on low then this same wire then gets maybe 9 volts or so and the voltage is dropped as it now goes through the clay resistor on the backside of the indash switch.

I really doubt on the motor you have that one wire is for low and the other for high BUT who knows. By looking at the assembly close if one wire was for low and one for high then the fan motor would have to be grounded through it's mounting in the rear deck. If the motor is attached to a plastic housing then there is no way the hosuing could become grounded unless there is a wire from the housing that went to a ground. Chances are you will only be able to wire up one speed with a standard on/off/on switch. If you really want two speeds then I'm thinking you will have to get a factory switch with the dropping clay resistor built onto it.

A test you could do is see if there is any resistance between the two wires to each other and then between the wires to the body of the fan.

Here are other shots of the Nova defroster I have for one of my cars:

http://rides.webshots.com/album/555174962lHuKhP

Be careful if you wire up a switch and make sure it can handle the amperage because if it cannot the switch will burn up. Also put the appropriate size fuse before the switch and run the right sized wire on it and then to the fan motor.

Jim
 

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Tim, I'm with you on this one. I am in the same dilema. I have a new harness and no switch. I have thought about trying to rig up a wiper switch if it would fit or made to fit in the original location at the bottom left side of dash and steering column. But, I don't know if it would be set up to funtion properly. The knob would look/be right, and the switch has off/slow(low)/faster(high) for possibly the fan speeds. It would turn on/off as original. A headlight switch might work too, but I don't like the idea of pulling it down for operation. I am not an electrical specialist concerning either switch on their funtionality aspect for possibly doing this procedure. I hope someone will know more about this and at least let us know if my idea is a total bust. Hope someone has some suggestions and good luck to us both! :)

J R
 

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Thanks flyingskibiker for the heads up. I suspected that it wouldn't work, but was unsure. I now remember the clay resistor you mentioned in your post. I guess more or less grasping at straws. Very seldom do you see the switch available. I think I have seen it maybe once in the last five years and it was for the whole setup, which I don't need and very expensive. JR

SOA-Nova is right concerning the one power wire for both speeds and the one ground wire, at least for the '67 and I believe the 68/69.

I guess the question still remains. What will work efficiently and safely until we find the actual switch?
 

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SOA-Nova is right concerning the one power wire for both speeds and the one ground wire, at least for the '67 and I believe the 68/69.

I guess the question still remains. What will work efficiently and safely until we find the actual switch?
Right now you could wire up an ON/OFF/ON switch and only have the switch work the high speed.

If you later find out what the resistor value is then this could be added to your switch to get the low speed.

As far as switches, let's say that the fan draws 10A of current then I would get a 20A switch. If the wire going to the fan is a 14 gauge, then extend this with a section of 14 gauge to the dash switch. From the dash switch use another section of 14 gauge wire to an inline fuse holder and from the fuse holder to the fuse block also use 14 gauge wire.

Since we don't know what size fuse was originally on this fan motor I would do some looking at wiring diagrams and see what shows up. It may be anywhere from 10A up to 25A but who knows. If for some reason it is fused at 25A, then a 30A switch should be used and not a 20A or smaller switch.

There are also ways to use low amperage switches and relays to work the fan also but only on high speed since we do not know what voltage the motor needs to be run on low speed.

Jim
 

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Flyinskibiker is right, you cannot use a wiper nor a headlight switch. You also cannot use a blower resistor assembly like what is on your heater/AC blower as it is not meant to be used outside of the blower housing. This resistor is meant to have air flowing over it to keep it cool and from burning up.

Jim
 

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My 69 Pontiac had a rear defroster like you describe, also my 76 Monte Carlo. Neatest thing since sliced bread. I think you need to do a junk yard search to find something simular out of another GM car.
 

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Discussion Starter #11
I have one of these switches somewhere, I will look for it tonight when I get home if that will help.
If you find this switch I would be definitely interested in it. Please shoot me a pm and let me know if you come up with it.

Btw, is it possible to use a 70 or later switch? The 70-78 camaros also used a fan defroster but I wasn't sure if these switches where made with the resistor built in too? I know they weren't cosmetically the same but if it functions exactly the same, I'm sure I could make something that will hold it to use.

If anyone knows this, please let me know that also. Thanks!
 

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Did you try calling Lectric Limited they seem to have everything even if it is not listed in the substantial catalog.
 

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Found it :)



Switch has 3 positions with the center being off. On Hi it passes the entire 12 volts, and on Low it passes about 11 volts.
Hope this helps.
Tom
 

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Discussion Starter #14
Hey Tom, I got your pm and responded back. Please let me know when you get it and let me know what you think. Thanks.

Also to anyone else, once again does any other cars use a resistor type switch for the defroster? For example, does the 70's camaros have a resistor switch?
I know it's not the same cosmetically but can it still work? Thanks. Can't seem to find any info on the wiring on this thing and was hoping that someone might know.
 

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Discussion Starter #15
As far as switches, let's say that the fan draws 10A of current then I would get a 20A switch. If the wire going to the fan is a 14 gauge, then extend this with a section of 14 gauge to the dash switch. From the dash switch use another section of 14 gauge wire to an inline fuse holder and from the fuse holder to the fuse block also use 14 gauge wire.

Since we don't know what size fuse was originally on this fan motor I would do some looking at wiring diagrams and see what shows up. It may be anywhere from 10A up to 25A but who knows. If for some reason it is fused at 25A, then a 30A switch should be used and not a 20A or smaller switch.

Jim
Hey Jim, looks like you're apart of all my threads. :hurray:
So, I think I may just go with a simple on off switch cause I really don't care about a 2 speed switch since I will probably barely use it, and as someone in another thread stated, the engine rumble is gonna drown out the fan on full speed anyway.

So to everyone out there, I went online and found some simple ON-OFF switches rated at 25amp at 12 volts. Do you think this is sufficient? I will also do the inline fuse too. I'm not a super electrical wiz and I was wondering if there is a way to see what the amps are that the fan draws.

If anyone can tell me how to test the fan for amp draw, that would be a big help so I can see if the 25 amp switch will be good enough, overkill OR not enough. Thanks
 

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Discussion Starter #16
Okay guys I just did a test with a meter to see the amp draw of the fan. Let me know if I did this right and if the results sound right.

I set the meter to 10A in the ADC section of the meter (I got this setup info online). I then connected the 2 meter leads "in series" to the ground wire and a seperate straight wire to the power wire on the motor. I connected the ends directly to the car battery, which was not connected to anything else at the time. The draw reads about 2.10 on the meter. So does that mean it's drawing a little more than 2 amps? OR do I have to times that number by 10 because it's on the 10A spot on the meter? If so does that mean it's a 21 amp draw?

Either way it is please let me know what size switch I should get if you know what these numbers mean. Any help with this would be great.

Thanks!
 

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Discussion Starter #18
You need to test for amp draw across the positive (red) side of the circuit, not the negative.
Okay thanks. So, I did do that and the result is exactly the same. 2.10 on the meter. So does that mean 2.1 or 21 amps drawn. Not really sure how to read meters all that well. Wasn't sure if it's like an rpm gauge and you have to multiply the number by 10 because I have the meter set on the 10A spot?
 

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From your readings your fan is drawing 2.1 amps so a 10 amp switch would be fine. I would probably start with a 7.5 amp fuse inline as well.
 
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