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2X12V Fan Relay Wiring....have I Got It Right?

Skylsh32

By Skylsh32,
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Skylsh32 Enthusiast

Skylsh32

Posted
Posted

Hey guys,

headlightrelaysetup.png

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here is a pic of how I imagine a fan wiring diagram would look like please if you can answer the questions in the pic (mind the font style) that'll be great I guess if the answer to question A was no then that'll pretty much answer them all. calculations of the 15amp fuse was done by adding the wattages of both fans in my case 80 watts per fan dividing them by 12 volts, which came out to approx 13amps for both fans joined on one power feed, however if each fan needed it's on power feed and own fuse then it'll be 10 amp fuse for each power source line. Just need someone to confirm that my setup is right, if it is not let me know what I need to change.

Thanks in advance.

t_revz Grand Master

t_revz

Posted
Posted

Your diagram won't work.

First use 20 amp fuse, power can be split to both relays or you can use 1 relay for both.

Now the part that's wrong is that the temp sensor is grounded(86)but the other side of the relay coil is also grounded(85) so it won't work. Either loop power from 30 and join to 85 or if you want put ignition to 85 so they turn off with ignition

Skylsh32 Enthusiast

Skylsh32

Posted
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Posted

Thanks Mate!

Here is a revised version I have come up with using 1 stock nissan relay from what I gather it is a 30A relay is that suitable for my application? unsure of the formulas needed to calculate correct relay amperage(will do some research) also I plan on running approx 13 gauge wiring for everything (power from fuse to relay, from relay to fan 1 then 2). except the switch wire(coolant temp sensor) which will just be something a little smaller. Looking at the diagram, how I plan to join fan 1 to 2 is this the correct way of doing it or does it not really matter?.

Again cheers for the help.

revisedfanwiring.png

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t_revz Grand Master

t_revz

Posted
Posted

Yep looks much better. 16ga (4mm2)should be enough for power wires but bigger is ok. Sensor wire can be as small as you want as its only 0.1amps or so.

Actually come to think of it, if it was me I would maybe double up the sensor wire and run it to a switch in the cab which then goes to ground so you can overide and turn on fans manually.

jjman Mentor

jjman

Posted
Posted (edited)

Actually come to think of it, if it was me I would maybe double up the sensor wire and run it to a switch in the cab which then goes to ground so you can overide and turn on fans manually.

bingo.

After a while of running my thermofan setup i did this. I never had a problem with the system failing n using it as a safety measure (tho it is certainly good for that- and needed).

The reason iv found a manual switch good is that you can switch it on if you know that you are about to be sitting in traffic/stop start etc and the temp will of course rise to the point of triggering the fans..

Instead of the temp needing to get up to the trigger point on your thermo switch n then activating (and staying on until it gets the excess heat out of the system), you just turn it on pre-emptively anyway so that things are kept cooler- it is easier to keep temps down than to drag higher temp out of a system.

Also it means that A: she will be nice n cool when the traffic clears n i want to get into som WOT straight away. B: so that when you do clear traffic n go WOT you have switched the thermofan off and as the system is cool it is also below the thermo trigger point so it stays off and you dont have the load of the thermofans running. Which is one of the main points of doing thermofans, not having a permanent and unnecessary load on the motor if it doesnt have to be there which gets you more power and response from the motor to the wheels- FTW

I did a trackday recently (skidpan so single 1-1,5 min laps) and i manually switched on the thermomfans while sitting in line before my lap so i had a nice cooler system n then swtiched off for the lap so no load on for the lap (n was below the thermoswtich temp so didnt come on). Worked really well.

Edited by jjman
blind_elk Grand Master

blind_elk

Posted
Posted

The small Bosch relays come in a variant that has 2 outputs, ie 2 x 85 (or maybe its 86). Makes wiring much easier, as the only duplicated wire is that from the relay to the fan(s).

t_revz Grand Master

t_revz

Posted
Posted

Yeah 30amp Bosch relays have 2 87 terminals. Just make sure the diagram on the side shows them joined together and 87a terminal isn't separate as that is a changeover relay. Pretty sure the 10 digit part number ends in 005

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