electric fans relay question.

rick lester · 06-09-2009, 02:32 AM

i just hooked up electric fans using a summit kit. fans are from a dodge status with dual fans. each fan is using its own relay and circuit breaker. the first time i hooked everything up i had circuit breakers mounted to fan shroud. fans would come on but not for long. they acted like they were getting power intermitted. ok i thought, maybe there overheating since there real close to radiator, even though directions say to mount everything close to what your powering, and relays were hot to the touch, but not the wiring (10 gauge for battery or +, 12 gauge for purple/ fan power, 14 gauge for yellow/ignition wire and grounds from fans..this is how summits dual fan relay is set-up) i moved the circuit breakers to the radiator support, and mounted about 6 inches from closest part of radiator. relays are mounted on inner fender a good foot from radiator. now neither circuit breakers or relays get hot but same thing is happening. if i cross over the "battery" and "aux" terminals on circuit breakers breifly fans work like there sopose to. checking amperage at circuit breakers when t-stat will turn fans on i get 14.2 amps and 12.1 amps on each fan with no spike. i have not checked amperage at fan (got to dark and mosquitoes love me for some reason). thats first thing on the agenda in the morning. i'm thinking IF i don't have a high amperage pull on fans and IF there is no spike at start-up, i have two bad circuit breakers. now if the circuit breakers are the culprit, can i just eliminate them all together. i do understand why they are there, but if i read correctly in the lastest issue of MM and FF they pieced together a similair system and i don't remember them using a circuit breaker. they used a dual fan with one relay and stated they had no problems. i'm using two relays with a dual fan set-up. let me tell you, when they are working they move A LOT of air and cool suburban down quickly, that is until circuit breakers give up. i'll tell you this much, i bought a HUGE aluminum radiator for a 454 suburban, and just idling without fans temp gauges goes no higher than 200 degress. let me know what you think. rick.

Dion Hildebrandt · 06-09-2009, 07:21 AM

hi Rick on my chevelle stocker i have dual caravan fans wired directly to power with no relays and no problems other than the crappy switch keeps coming apart. those fans will pull the race car down to zero faster than i can do my post run paper work.

njk53 · 06-09-2009, 07:53 PM

I would not remove the relays because the purpose of the relay is to prevent voltage/amperage drop across the wiring circuit. Your fans will not operate at peak performance without the relay. I am not sure why you use two relays but I guess it is OK. My brother and I have a BB Chevelle Wagon Stocker and we used a single fan assembly off of a Cadillac XLR. The XLR uses the top of the line Siemens fan motor that put out over 1000 CFM. There was little modification to adapt it to the Chevelle radiator and looks like it is suppose to be there and performs flawlessly. We just use an on/off switch on our panel. We used a Bosch relay with an in line fuse.

If you are interested, I think I still have the schematic we used on our car at the shop. If I still have it I can e-mail you a copy. It sounds like you are using a thermistor to sense radiator temperature to turn the fans on and off correct?

STOCK1278 · 06-09-2009, 09:25 PM

Had a similar problem on a car I did. Circuit breakers wouldn't work with 16volt batteries. Bypassed relays and everything is fine. Would love to know the answer to the question. Didn't have diagnostic tools at the time. Fans were GM, Relays were Jegs.

Tom Goldman · 06-09-2009, 09:27 PM

move the circuit breakers away from the radiator....the breakers can absorb additional heat from the radiator,and fool it into opening earlier than the rated current. ....breakers have a bimetal strip that moves when it gets hot,additional ambiant heat will lower the effective current rating of the breaker......Ideally the breaker should be located as close to the power source as practical......keep the relays, the voltage drop across a switch circuit on a cooling fan can be substantial. ....the purpose of the relay is to provide optimum voltage to the load while utilizing as little current as possible on the control side of the circuit. ......Tom

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, 02:32 AM	#1
rick lester Member Join Date: Oct 2004 Location: Littlestown PA Posts: 163 Likes: 9 Liked 4 Times in 1 Post	electric fans relay question. i just hooked up electric fans using a summit kit. fans are from a dodge status with dual fans. each fan is using its own relay and circuit breaker. the first time i hooked everything up i had circuit breakers mounted to fan shroud. fans would come on but not for long. they acted like they were getting power intermitted. ok i thought, maybe there overheating since there real close to radiator, even though directions say to mount everything close to what your powering, and relays were hot to the touch, but not the wiring (10 gauge for battery or +, 12 gauge for purple/ fan power, 14 gauge for yellow/ignition wire and grounds from fans..this is how summits dual fan relay is set-up) i moved the circuit breakers to the radiator support, and mounted about 6 inches from closest part of radiator. relays are mounted on inner fender a good foot from radiator. now neither circuit breakers or relays get hot but same thing is happening. if i cross over the "battery" and "aux" terminals on circuit breakers breifly fans work like there sopose to. checking amperage at circuit breakers when t-stat will turn fans on i get 14.2 amps and 12.1 amps on each fan with no spike. i have not checked amperage at fan (got to dark and mosquitoes love me for some reason). thats first thing on the agenda in the morning. i'm thinking IF i don't have a high amperage pull on fans and IF there is no spike at start-up, i have two bad circuit breakers. now if the circuit breakers are the culprit, can i just eliminate them all together. i do understand why they are there, but if i read correctly in the lastest issue of MM and FF they pieced together a similair system and i don't remember them using a circuit breaker. they used a dual fan with one relay and stated they had no problems. i'm using two relays with a dual fan set-up. let me tell you, when they are working they move A LOT of air and cool suburban down quickly, that is until circuit breakers give up. i'll tell you this much, i bought a HUGE aluminum radiator for a 454 suburban, and just idling without fans temp gauges goes no higher than 200 degress. let me know what you think. rick.

06-09-2009, 07:21 AM	#2
Dion Hildebrandt Member Join Date: Nov 2008 Location: calgary alberta canada Posts: 383 Likes: 0 Liked 0 Times in 0 Posts	Re: electric fans relay question. hi Rick on my chevelle stocker i have dual caravan fans wired directly to power with no relays and no problems other than the crappy switch keeps coming apart. those fans will pull the race car down to zero faster than i can do my post run paper work. __________________ Dion Hildebrandt 6009 STK H/SA

06-09-2009, 07:53 PM	#3
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	Re: electric fans relay question. I would not remove the relays because the purpose of the relay is to prevent voltage/amperage drop across the wiring circuit. Your fans will not operate at peak performance without the relay. I am not sure why you use two relays but I guess it is OK. My brother and I have a BB Chevelle Wagon Stocker and we used a single fan assembly off of a Cadillac XLR. The XLR uses the top of the line Siemens fan motor that put out over 1000 CFM. There was little modification to adapt it to the Chevelle radiator and looks like it is suppose to be there and performs flawlessly. We just use an on/off switch on our panel. We used a Bosch relay with an in line fuse. If you are interested, I think I still have the schematic we used on our car at the shop. If I still have it I can e-mail you a copy. It sounds like you are using a thermistor to sense radiator temperature to turn the fans on and off correct? __________________ Nelson Kowal Stock 345

06-09-2009, 09:25 PM	#4
STOCK1278 Junior Member Join Date: Dec 2005 Location: New Windsor, NY Posts: 43 Likes: 0 Liked 0 Times in 0 Posts	Re: electric fans relay question. Had a similar problem on a car I did. Circuit breakers wouldn't work with 16volt batteries. Bypassed relays and everything is fine. Would love to know the answer to the question. Didn't have diagnostic tools at the time. Fans were GM, Relays were Jegs. __________________ Jason M Silver NHRA Stock Eliminator - 1278 88 Oldsmobile Cutlass 307/213

06-09-2009, 09:27 PM	#5
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,473 Likes: 879 Liked 858 Times in 234 Posts	Re: electric fans relay question. move the circuit breakers away from the radiator....the breakers can absorb additional heat from the radiator,and fool it into opening earlier than the rated current. ....breakers have a bimetal strip that moves when it gets hot,additional ambiant heat will lower the effective current rating of the breaker......Ideally the breaker should be located as close to the power source as practical......keep the relays, the voltage drop across a switch circuit on a cooling fan can be substantial. ....the purpose of the relay is to provide optimum voltage to the load while utilizing as little current as possible on the control side of the circuit. ......Tom __________________ Tom Goldman 1500 SG , 1506 STK

06-09-2009, 10:11 PM	#6
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	#7
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	#8
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.