Could this start a fire?
Thread Starter
Instructor
Joined: Dec 2004
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Could this start a fire?
When i bought my 85 the previous owner had installed a switch to turn on the fan. My fan stopped working and I noticed the switch was loose and then I noticed that the wire was hot (i burned my finger). So I replaced the switch with a 50 watt switch (the wire is thick). I use to have a camaro and I did the same thing but I spliced used the grounding technique. This previous owner for whatever reason directly has one wire to the battery and the other to the fan. Is this safe or can it cause a fire. I replaced the switch about six months ago but I never noticed the wire was hot until now. Thanks.
Drifting
Joined: Sep 2005
Posts: 1,867
Likes: 3
From: Pasadena Maryland
NO If the wire is hot to the touch it is too small for the current load. That's where ripped 78 says to use a relay. You let the relay carry the high current and the switch only turns the relay on and off. Look in your fuse box on the car, I don't think they even make a 50 amp fuse. If your fan is pulling that much current there is something wrong with it!
Thread Starter
Instructor
Joined: Dec 2004
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The wire thats on there is pretty thick its the kind that barely bends. What kind of relay should I get. And also, what would cause the wire to get that hot? I just replaced the fan not to long ago. Thanks for all the replies. Where would I put the relay inbetween the battery and the switch. 
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by batoutofhell
The wire thats on there is pretty thick its the kind that barely bends.
Originally Posted by batoutofhell
What kind of relay should I get.
Originally Posted by batoutofhell
And also, what would cause the wire to get that hot?
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Drifting
Joined: Sep 2005
Posts: 1,867
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From: Pasadena Maryland
I don't know, maybe radio shack, or try auto parts store? The relay would get wired to the fan with power and ground. The the switch would wire to the relay. When you turn the switch on the relay contacts close and turn on the fan. So the switch only activates the relay, not the load that is on the relay. The relay should have a wiring diagram on it or with it when you buy it. Bad or loose connections will cause heat, that is how curcuit breakers work. Check all wires, connections and grounds for loose or bad connections. Try to keep all wires as short as poosible, the longer the wire the less current it can carry. But it seems to me that if the wire itself is getting hot the fan is pulling too much current. Can you find out from the fan's manufacturer how much current it is supposed to draw? That will tell you how big the relay and the wires need to be.
Thread Starter
Instructor
Joined: Dec 2004
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wow the previous owner really mickey moused this one, I guess he totally bypassed the fan relay since its running directly from the battery. Where is the fan relay located on the 85? I think i'll buy another one and hook it up the proper way.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by batoutofhell
Where is the fan relay located on the 85? I think i'll buy another one and hook it up the proper way.
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Advanced
Joined: Oct 2005
Posts: 74
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From: Halifax Va
Cruise-In VII Veteran
Originally Posted by batoutofhell
The wire thats on there is pretty thick its the kind that barely bends. What kind of relay should I get. And also, what would cause the wire to get that hot? I just replaced the fan not to long ago. Thanks for all the replies. Where would I put the relay inbetween the battery and the switch.
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
Switches are not rated in watts, they are rated for current and voltage capacity. Your fan draws 14 amps when running and it is powered by a relay that is fused. If you want to manually switch your fan on, wire your switch to ground the fan relay coil that is grounded by the ECM. On my 87 vette, this wire is green/white and the relay coil wire that has 12v when the ignition sw is in RUN position is dark blue. Your 85 probably has the same wire colors. 14 amps through a too small wire and switch will make them hot! Relay coils draw very little current and small size wire and a small switch can be safely used to operate the coil of a relay.
Last edited by jfb; Jan 7, 2006 at 12:45 AM.
Le Mans Master
Joined: Dec 2004
Posts: 5,789
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From: Myrtle Beach SC
St. Jude Donor '05-'06
Originally Posted by batoutofhell
If it melted a 50 watt switch, what amp of fuse do you think I should use and again is this normal for the wire to be that hot, I never touched a wire that was hot before. Thanks.
To find out what fuse is needed find out the amperage of the motor.I would guess it is more than 5 amps which is what a 60W switch would handle at 12V.The wire guage is important too 14g can handle 15 amps 12gcan take 20.I bet the wire is the wrong size.
http://www.powerstream.com/Wire_Size.htm