Fan relays - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chevyguy_72 · 11-18-2005, 10:51 AM

I am looking for the inexpensive way to wire the dual electric fan set-up i have my truck. I don't want to spend a ton on it but will buy a pre fabed harness or i could probably make one if someone could provide me with the proper info. I am looking to go the relay route with a temp switch.
Thanks

red71cheyenne · 11-18-2005, 12:15 PM

My fans are running off of one relay. Not sure if its SPDT or DPDT, but I'll look this afternoon. I just have it turning on both fans whenever the temp gets high enough(temp switch). Also have an input for if A/C is on to have the fans on as long as the A/C compressor is running. There are several different ways you can go. Summit, Jegs and even JC Whitney sell wiring/relay harnesses to get you hooked up if you don't want to engineer the system yourself. My thermostat is also adjustable, so I can set it to come on when I want. Jeff.

Russell · 11-18-2005, 12:42 PM

Here is how I have my duals wired up.

I have a larger fan, and a smaller fan. Larger fan is operated by my TPI's ECM, along with a switch under my dash, while the smaller fan is operated by a temperature switch installed in my passenger side head, along with the same switch under my dash.

This way, should either my ECM's fan relay driver, or temperature switch fail, I still have the ability to turn my electric fans on when I feel I need them.

I used a pair of Bosch 40 amp relays with diodes in them to prevent damage to the relay by the fan producing voltage while it is still spinning, but has been turned off. I am using a 20 amp fusible link to provide power to the fans. You can adjust how you hook up the fans, by changing how you hook up the ground wires for the relays (connect them both together to turn both fans on at once etc) but I would highly suggest using two relays, and use good quality ones, like the Bosch 40 amp mini-cube relays I used.

The very last thing you want is for your only relay to burn out, and to be left without a fan! Thats why to run duals, then if one fails, you still have the other fan for cooling till you replace the relay.

Thats another reason why I suggest Bosch relays. They are the industry standard now, and every single relay on my truck is a bosch mini-cube now. I've got two spares to keep in my glove box, so if anything fails (headlights, horn, fans, etc) I can just pull one out of the glove box, and quickly and easily replace the broken one

red71cheyenne · 11-18-2005, 12:48 PM

Good idea having a backup. Course if my relay fails, I'll just jumper it to 12V to get me home. May have to look at re-engineering mine to encompass a backup plan. Thanks Russell!

chevyguy_72 · 11-18-2005, 01:01 PM

thanks any other routes would be great too.
keep them coming

farside847 · 11-25-2005, 03:18 PM

Would summit part number PRF-30103 fit a standard radiator? Seems like a complete wire kit....

11-18-2005, 10:51 AM	#1
chevyguy_72 Vintage Evil Join Date: Aug 2005 Location: Broomfield, CO Posts: 956	Fan relays I am looking for the inexpensive way to wire the dual electric fan set-up i have my truck. I don't want to spend a ton on it but will buy a pre fabed harness or i could probably make one if someone could provide me with the proper info. I am looking to go the relay route with a temp switch. Thanks Last edited by chevyguy_72; 11-18-2005 at 10:52 AM.

11-18-2005, 12:15 PM	#2
red71cheyenne Back in the sticks Join Date: Jan 2001 Location: Fordland, MO Posts: 3,188	Re: Fan relays My fans are running off of one relay. Not sure if its SPDT or DPDT, but I'll look this afternoon. I just have it turning on both fans whenever the temp gets high enough(temp switch). Also have an input for if A/C is on to have the fans on as long as the A/C compressor is running. There are several different ways you can go. Summit, Jegs and even JC Whitney sell wiring/relay harnesses to get you hooked up if you don't want to engineer the system yourself. My thermostat is also adjustable, so I can set it to come on when I want. Jeff. __________________ 1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty

11-18-2005, 12:42 PM	#3
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Re: Fan relays Here is how I have my duals wired up. I have a larger fan, and a smaller fan. Larger fan is operated by my TPI's ECM, along with a switch under my dash, while the smaller fan is operated by a temperature switch installed in my passenger side head, along with the same switch under my dash. This way, should either my ECM's fan relay driver, or temperature switch fail, I still have the ability to turn my electric fans on when I feel I need them. I used a pair of Bosch 40 amp relays with diodes in them to prevent damage to the relay by the fan producing voltage while it is still spinning, but has been turned off. I am using a 20 amp fusible link to provide power to the fans. You can adjust how you hook up the fans, by changing how you hook up the ground wires for the relays (connect them both together to turn both fans on at once etc) but I would highly suggest using two relays, and use good quality ones, like the Bosch 40 amp mini-cube relays I used. The very last thing you want is for your only relay to burn out, and to be left without a fan! Thats why to run duals, then if one fails, you still have the other fan for cooling till you replace the relay. Thats another reason why I suggest Bosch relays. They are the industry standard now, and every single relay on my truck is a bosch mini-cube now. I've got two spares to keep in my glove box, so if anything fails (headlights, horn, fans, etc) I can just pull one out of the glove box, and quickly and easily replace the broken one Attached Images __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap) Last edited by Russell; 11-18-2005 at 12:45 PM.

11-18-2005, 12:48 PM	#4
red71cheyenne Back in the sticks Join Date: Jan 2001 Location: Fordland, MO Posts: 3,188	Re: Fan relays Good idea having a backup. Course if my relay fails, I'll just jumper it to 12V to get me home. May have to look at re-engineering mine to encompass a backup plan. Thanks Russell! __________________ 1971 Cheyenne C-10 w/700R4 and Tuned Port Injection 1969 K5 Blazer w/Tuned Port 2010 2SS/RS Flaming Orange Camaro 2011 K1500 Suburban 2014 K1500 Pickup 2008 Nissan Altima? The wifes' hoopty

11-18-2005, 01:01 PM	#5
chevyguy_72 Vintage Evil Join Date: Aug 2005 Location: Broomfield, CO Posts: 956	Re: Fan relays thanks any other routes would be great too. keep them coming

11-25-2005, 03:18 PM	#6
farside847 Registered User Join Date: Feb 2005 Location: Bay Area, California Posts: 995	Re: Fan relays Would summit part number PRF-30103 fit a standard radiator? Seems like a complete wire kit.... __________________ 1971 Chevy C10 Shortbed Stepside, 307v8 3-on-the-tree



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