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Electric fan wiring opinion

91vert

New Member
I found a new fan for a Sonota - it does not list the amps , but has wiring harness that offers 2 speeds ( I will try the lower speed first to see how it cools ) I needed to trim the sides off but it fits perfect over the single core radiator - gives 1 “ clearance from water pump . I was able to secure it tight with 5 zip ties ( I will add some L brackets soon ) my question is : I want the fan to come on when car is turned on . I bought a 100a relay switch that is pretty straight forward , but I am unclear on a few things . the fan has 2 wires , does the fan get grounded to the car body ? If so , why does the rely need to be grounded ? Also , the “positive trigger” on the relay is simple the ignition wire ( like a car radio or amplifier ? ) 2391239123922393239223922394
 

broncojunkie

Active Member
The positive trigger wire going to the relay would need to come from some type of switch. A simple 12v switch on your dash could provide that signal, but it sounds like you're wanting the fan to be controlled automatically. So you'll need a fan controller of some type.

I use a simple aftermarket non-adjustable one on my pace car. It's set to kick on at 185 degrees, iirc. I have a cheap adjustable one on my 88gt. I think it came from autozone. It works great, but when I purchased one for my pace car, 2 of them failed within a day or 2 (which is why I went with the non-adjustable one from summit or jegs).
 

broncojunkie

Active Member
Also, some folks have been using a Volvo fan controller. They can be found cheap in the junkyards and they're good quality. I don't have the specific, but I'm sure Google would bring it up.
 

broncojunkie

Active Member

This is the one I'm using. It has a small thread-in temperature sensor, instead of the probe type that pushes into your radiator. Mine is threaded straight into the aluminum radiator tank, after I had a bung tig-welded in. There are other ways to mount it. For instance, they make an aluminum coupling with a threaded hole. You simply cut your radiator hose and install inline. I actually have one sitting in my garage waiting for my next project (79 cobra). They're about $8 or so on Ebay.
 

91vert

New Member
I simply want the fan to come on when car is running - would any ignition on wire be sufficient ? Also what is the purpose to ground the actual relay switch if the fan is grounded ? 23982399
 

broncojunkie

Active Member
The ground for the relay is to operate the electrical switch, which allows the relay to operate. In essence, it is an electrical device in its own right and needs a ground to complete the circuit that functions as an electromagnetic switch. Hope that makes sense!

And yes... you certainly can wire your fan up the way you describe, simply by tapping in to a 12v switched source. It will be running whenever the key is on (engine running). Although guys have been wiring them that way for years, it's not ideal. When you're idling or slowly putting around town, the fan needs to run to provide air flow. At highway speed, the fan running will actually reduce air flow. That's the way I understand it, anyway. Electric fans may also benefit from kicking on and off... basically, allowing them to rest so the electric motor doesn't get too hot and fail prematurely. So that's what I suggest... but like I said... people have been wiring them that way since as long as I can remember (typically after a sensor or switch failure) and I don't think I've ever heard of any confirmed issues with it.
 

91vert

New Member
Thanks ! - I will save my fan clutch and OEM fan in case the electric does not work out and keep temps cool -
 
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