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Old 11-12-2013, 09:05 PM
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Electric Fan tripping circuit breaker

Hey guys My 1974 Chevrolet C10 is giving me some trouble. The truck has an electric fan that has allways been wired up to be on when the ignition is on. I got tired of this and bought a thermal switch kit and installed it to turn my fan on when the engine reaches 200. Heres the kit I got....... http://www.summitracing.com/parts/sum-890016/overview/

The thermal switch seamed to be working flawlessly until my buddy and I were stuck in line at the In-n-Out Burger drive through. I watched my temp gauge climb and heard the fan try to come on. I noticed a good 1.5-2 volt drop fluttering on my gauge. The fan never came on I had to pull snip a wire and run it to my fan to get it to turn on manually. I read about installing a manual override switch so today I did just that. Repaired my cut wire. Connected my toggle switch to the thermal sensor wire and ground, flipped the switch and bam fan on. Problem solved??? NO I fired my truck up and let it warm up went to toggle my fan override switch on. I heard my fan try to start but just getting weaker and weaker sounding then no fan spinning at all. then the 30 amp breaker clicking so I turned the toggle off. No fan What could cause this? If I just disconnect the 12v key on wire from the relay and connect it to the fan motor + The fan works.

Anybody able to help me get through this wiring nightmare? Im actually pretty decent at wiring now from dealing with guitars and my dang trucks crap wiring harness.

Heres the current fan wiring. I have it just like the diagram shows with the optional override switch installed. http://static.summitracing.com/globa...20890016-a.pdf

Ive been looking at http://www.madelectrical.com/electri...evymain1.shtml and theres great info but i could really use some help making sense of this whole wiring problem. Thanks for your time guys! I appreciate all the help and great knowledge I receive from this forum Ive actually recently dropped a L31-R Vortec 5.7L and had my Th375 rebuilt by a great local tranny man ;D Trucks been running like a dream but theres allways these little pain in the butt problems like my fan.... Im about to just bolt on a normal fan and be done with it


Last edited by GUITAR1989; 11-12-2013 at 09:16 PM.
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Old 11-13-2013, 05:44 AM
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Sounds like a resistance problem with the fan power wire. What size is it? It should be at least 10ga. If it is to small, is starting to break down or there is a lot of resistance in your splices or crimp connections that can cause the problem you are seeing. Check your wires and connections for evidence of melting.

Last edited by astroracer; 11-13-2013 at 05:52 AM.
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Old 11-13-2013, 09:04 AM
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Things to check: wire size to fan, size of circuit breaker or fuse, Fan may be going bad pulling too many amps.

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Old 11-13-2013, 09:21 AM
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I have had the same thing happen to me with the first set of electric fans I installed on my 02 Silverado. I found that the fans I had were drawing way too much amperage. I fried 3 control units and 1 battery. I changed my dual fan setup to 2 smaller flex fans that move more air and I have had no problems with it.
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Old 11-13-2013, 02:26 PM
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Make sure the fan runs OK. Put a jumper directly to the fan motor to see if it works.
The tripping 30 amp breaker leads me to think the fan is bad or a mouse family moved in.

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Old 11-13-2013, 04:04 PM
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You must have a fan pulling higher amps,swap to this:FRYS.com*|*NTE The popular Lincoln MK VIII fan and some other hi-flow fans will not support a single 30 amp relay,you should also have an alternator capable of 100 amps plus with some fans.For a relay education read this:http://www.watsons-streetworks.com/tips Click on "current tips".
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Old 11-13-2013, 07:13 PM
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something also to remember, if you feed your fan with a #10/30A wire, you should also run a #10 ground wire. Also make sure all your grounds are good; Batt. to block; block to firewall; Batt. to fender.
Read the Watson info, excellent !
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