electric fans relay question.

rick lester · 06-09-2009, 10:11 PM

this afternoon i thought about the circuit breakers still being too close to the radiator. so i took them off the radiator core support and actually had them laying on my work cart with wires running from relays to circuit breakers then to battery. yes lots of wires but circuit breakers were no where near a heat sorce. same thing happened. next then was i checked aperage at fans, 12.2 for both directly to the battery with no spike at start-up. the only thing i can think of is the circuit breakers are bad. i wired without circuit breakers and checked everything with while it was working. i found no spiking, nothing over 12.9 amps pooled when fans come on combined at battery ( i had wires from both relays to battery wired together to single wire then to battery, but that not how i will have it set-up permenatly ), so i am eliminating circuit breakers. the reason i went with dual relays is to make sure i don't overload one with a dual fan set-up. this will be a daily driver/tow vehicle/long distance hauler for trips. if i would have used one relay for two fans and the relay goes out, then i would have no fans. this way if one goes out i have the second to use. single relay with dual fans works fine on a race car. i caution on the side of safety when it comes to electrical. i did learn something today, even when the fans shut off, there is still current untill fans stop completlyeven with no electric going to fans. i always assumed when power was shut off there would be no power. i'm assuming since fan is built like a mini generator its still has juice until it "powers down". 39 and still learnig something new everyday.

Bill Harris · 06-10-2009, 07:36 AM

You never say what the circuit breaker ratings are. What amperage are they supposed to open?

I think I would ditch the circuit breakers and replace them with an ATO style fuse. You can get a nice in-line ATO fuse holder from Digi-key:

http://search.digikey.com/scripts/Dk...&name=F1086-ND

Put a 20A fuse inline to each fan and be done with it.

You are correct about the powered-off fan; a free-wheeling DC motor is a generator.

rick lester · 06-10-2009, 10:40 PM

circuit breakers are rated at 30 amps, just like the relays. been two days and all is fine. one bad thing is stock 1988 chevy suburban temp. gauge is off by 20 to 25 degrees. fans come on at 185, gauge reads between 205 and 210. i'm assuming since its a 185 on, 175 off thermostatic sensor since thats what i ordered. one thing i did do different than the directions said, i hooked the yellow wires to a live slot in fuse box instead of to ignition. this way the fans stay on until its cooled down to 175, even if the suburban is shut down. rick.

06-09-2009, 10:11 PM	#1
rick lester Member Join Date: Oct 2004 Location: Littlestown PA Posts: 163 Likes: 9 Liked 4 Times in 1 Post	Re: electric fans relay question. this afternoon i thought about the circuit breakers still being too close to the radiator. so i took them off the radiator core support and actually had them laying on my work cart with wires running from relays to circuit breakers then to battery. yes lots of wires but circuit breakers were no where near a heat sorce. same thing happened. next then was i checked aperage at fans, 12.2 for both directly to the battery with no spike at start-up. the only thing i can think of is the circuit breakers are bad. i wired without circuit breakers and checked everything with while it was working. i found no spiking, nothing over 12.9 amps pooled when fans come on combined at battery ( i had wires from both relays to battery wired together to single wire then to battery, but that not how i will have it set-up permenatly ), so i am eliminating circuit breakers. the reason i went with dual relays is to make sure i don't overload one with a dual fan set-up. this will be a daily driver/tow vehicle/long distance hauler for trips. if i would have used one relay for two fans and the relay goes out, then i would have no fans. this way if one goes out i have the second to use. single relay with dual fans works fine on a race car. i caution on the side of safety when it comes to electrical. i did learn something today, even when the fans shut off, there is still current untill fans stop completlyeven with no electric going to fans. i always assumed when power was shut off there would be no power. i'm assuming since fan is built like a mini generator its still has juice until it "powers down". 39 and still learnig something new everyday.

06-10-2009, 07:36 AM	#2
Bill Harris Member Join Date: Mar 2002 Location: Ooltewah, TN Posts: 421 Likes: 13 Liked 26 Times in 13 Posts	Re: electric fans relay question. You never say what the circuit breaker ratings are. What amperage are they supposed to open? I think I would ditch the circuit breakers and replace them with an ATO style fuse. You can get a nice in-line ATO fuse holder from Digi-key: http://search.digikey.com/scripts/Dk...&name=F1086-ND Put a 20A fuse inline to each fan and be done with it. You are correct about the powered-off fan; a free-wheeling DC motor is a generator. __________________ Bill Harris ex 2172 STK ex 2272 S/S

06-10-2009, 10:40 PM	#3
rick lester Member Join Date: Oct 2004 Location: Littlestown PA Posts: 163 Likes: 9 Liked 4 Times in 1 Post	Re: electric fans relay question. circuit breakers are rated at 30 amps, just like the relays. been two days and all is fine. one bad thing is stock 1988 chevy suburban temp. gauge is off by 20 to 25 degrees. fans come on at 185, gauge reads between 205 and 210. i'm assuming since its a 185 on, 175 off thermostatic sensor since thats what i ordered. one thing i did do different than the directions said, i hooked the yellow wires to a live slot in fuse box instead of to ignition. this way the fans stay on until its cooled down to 175, even if the suburban is shut down. rick.

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