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Idea for dual fan 2 speed relay setup


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Got it figured out. takes 2 4 pole relays and 1 5 pole relay. Low speed basiclly will be on all the time. high speed comes on with a temp sending unit.

 

easy to copy and it works!

 

http://i5.photobucket.com/albums/y196/gearhead559/2speedfanwiring.jpg

now i was going to draw the insides of the relays in there to help you understand how it works, but just didnt have the room for it.

lmk what you think.

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how you figure that when this is the way that every gm/kia and some others run them? :confused: now 16 volts that will kill it. tthey run in series on low 12 volt's when the sending unit grounds they both get 12 volts instead of sharing it.
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odd because thats the same wireing that GM used on the F-body and they didn't fail. 3 relay setup just like that.

same damn wiring kia uses aswell. how the hell is a 12 volt motor going to fail on 6 volts. IT WONT IT WILL RUN AT HALF SPEED. :rolleyes:

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it still have 12v its just run is series insted of parallel the amps are just cut in half to run the fans slower. the 3rd relay turns it on and off from series to parallel.

i know this

;)

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you also have it drawn so that if fan one fails on low neither fan will run not something I would care about on a kia, but I'd be concerned about no fail safe on a perf application, unless it automatically puts the other fan on hi speed if the other fails?
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one fan will still on high, if one fails. that if the motor is open! now if the motor shorts, it would pop the fuse. and there is no way this system can work witha 3 wire fan like froma contour
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from pin 87(relay far right) to pin 30(middle relay) and come out pin 87a of the same relay. at this point the 2 fans share 12 volts . and in which case doing a voltage drop across either fan will show 6 volts. this is how they run in series.

now when the middle relay is energized it it will ground the one fan(far right) while the other fan will get full power from the relay on the far left.

hence on low they run in series. on high they both have there own power supply and there own relay. Simple Gm wiring is all this is. only difference is ecu's/pcm's are used to control the ground side of the relays. instead of a switch and a grounding temp sensor like im going to use.

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How can you run both fans in series when the 1st fan is grounded all the time? To run both fans in series then change to parallel you would need dpdt relays....

 

thats how series works, battery feed to device (+), device (-) to other device (+) and other device (-) to ground.

 

low speed = relay 1 and 2 off and relay 3 on.

high speed = relay 1, 2 and 3 on.

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