I am trying to fabricate something to turn on and off an electric fan, and am wondering if the fan relay switch grounds through the switch. I would like to connect a switch up to a 12V constant and use the switch to cool the engine. The switch is out of an 86 TA. Is there anything else to consider? Thanks for your help...

 

A relay can be wired to switch either side of a circuit.

I'm not exactly sure what you are trying to do here, but I'll take a stab at it.

You don't need a relay if your switch is going to have 12V+ on it. Just run the 12V+ from the switch to the fan. Make sure to use appropriate size wire and fuse.

 

Open the attached thread. Then, scroll down to the bottom of the product listing, you'll see Wiring harness Instructions. Click on that. It'll open and show you a wiring diagram. When I wired in my switch and relays, I found it very handy.
http://store.summitracing.com/partde...5&autoview=sku

 

You can use the stock fan relay. The relay control is a ground lead that, in stock form, grounds thru the temp switch or AC pressure switch. No reason you couldn't run this same ground lead through a manual switch.

You do not want to run your primary fan power through a switch. The amp draw will require more expensive wire and a heavier duty switch. Even if you buy a new stock style relay it will only run around $15 or so.

 

Ok, here is what I am thinking, I have an older Chevy from the 1950s with a hole in the head that looks like I could take a fan relay switch/sensor and bolt it in and get rid of the manual fan and use an electric fan. I want to use the sensor to control the on/off of the fan.

I think I could use this but am not sure of how to wire it. If the switch grounds through the head, then I should have no problem just hooking up a constant power source and letting the switch do its work.

 

The switch should ground through the head but you MUST run the primary power to the fan through a relay. Putting that many amps through the sensor to the head is a bad idea.

Check a wiring diagram for any third gen and trace the fan motor power and control wiring. Pretty simple AND easy.

 

so i do need a relay. thanks for your help!

 

Yeah, you can pull a relay off at a JY for next to nothing or buy a replacement relay at AZ or the equivalent for around $15. Best to hit the JY though as you'll need the four-plug pigtail for it or have to fashion one.

The single fan assembly from a JY with associated shroud, wiring, pigtails and sensor will work fine for a mild performance engine. If you need it all, best to pull it all at once and replace the wiring with new and the fan motor, if needed.

 

Thanks again for the follow up, I am gonna try to do this before summer.