silly wiring question

twilightprotege · Post by **twilightprotege** » Sat Jan 16, 2010 1:50 pm

when i finish wiring up my new radiator fans and i want to use the stocko wiring to trigger the new fans through a relay, i'm pretty sure i cant just hook up the wires to the relay. i think i need a resistor of some sort so the wires dont overload and burn out or burn out the fuses. is this right? if so, what sort of resistor should i use? just a 1.5K one (i think that's how they work)? i've used a resistor on an air temp sensor on my astina so i know that works, just need some reassurance that i'm doing the right thing basically

steptoe · Post by **steptoe** » Sat Jan 16, 2010 4:02 pm

I just used a new power source to switch through to fan relay, and fan gets fused battery power.

twilightprotege · Post by **twilightprotege** » Sun Jan 17, 2010 11:56 am

well i tried the resistor but the fan now doesnt turn on - it does turn on without the resistor.

maybe the resistor is rated too high? also, i've seen on the offroadingsubarus website that they do a similar thing with headlights, but they put a 100ohm resistor between the 85 and 86 pins on the relay - is that what i should be doing instead????

i'm confused...

tex · Post by **tex** » Sun Jan 17, 2010 12:07 pm

I don't realy understand what your trying to do I'll have to read it again later but why not find the old signal wire to the relay and use that to power your new wires and relay. Also you can buy a relay with the resistor internally but if you put it in series with your fan it'll either turn into a fuse or possibly burn it out depending on resistance and wattage or in parralell it will drop the voltage either slowing it down or not let it run.

discopotato03 · Post by **discopotato03** » Sun Jan 17, 2010 12:25 pm

If you are doing your own power supply which I would in an old car you don't need resister relays . All you need to do is place a fuse in line as close to the power source as practical to protect it . The relay needs a trigger and thats where the temp probe comes in . Probably want to get the AC system to do the same if you have that as well .

A .

twilightprotege · Post by **twilightprotege** » Sun Jan 17, 2010 12:37 pm

dont worry, all works now. i put the resistor between 85 and 86 and it works fine now. the fusable links arent smoking anymore (lol)

twilightprotege · Post by **twilightprotege** » Sun Jan 17, 2010 9:02 pm

nope, still doesnt work and causes the fusable links to smoke...

attached is what i'm trying to do. basically replace the stock electric fan with a relay. however when i do this, it's like creating a short (positive from the ecu connected straight to the ground, but through the relay) and that is why the fusable links start smoking.

i tried placing a resistor on the ground wire after the relay. the resistor i used was a 1W 1.5K, but when i did this, the relay didnt trip. should i try a lower ohm resistor? maybe try the other wire incase i thought the ground wire was actually the power wire?

the next thing i tried was placing a resistor (1W 1.5K) between the 85 and 86 pins on the relay. the fans worked, but after a test drive tonight, the fusable links still smoke - obviously no good.

what should i do???

steptoe · Post by **steptoe** » Sun Jan 17, 2010 10:45 pm

This is on the L Series RX?
Or something else?
Stock fan or fans - which one(s)

Stock ECU ? Don't switch fans do they?

You'd think the positive to the relay would be straight to it through ignition and fuse and the earth was doin the switchin' (through ECU ) ECU seem to do earth switching for things, think injectors, the get pos power at ignition but ECU gives them the neg earth to make em spray.

With relays 85 is regarded as the earth pin and 86 gets the switch on power connection. Most relays will work with earth hooked up to 86 and power to 85, but when it comes to diode protected internally relays things come unstuck

85 to Earth, come in Earth - just sort of remember in my own special way

twilightprotege · Post by **twilightprotege** » Mon Jan 18, 2010 8:01 am

yep L RX. and it's on the stock a/c fan, although there wasnt one on my car to begin with, the plug was still there.

yeah most of the time the ecu's switch the earth on or off.

it should never matter which way you wire up the relay as the power going through the relay does nothing but go through the middle of a coil. the power going through the coil makes a small magnetic field that attracts the clicker thingie arm and then allows the power to go through the other pins. it shouldnt matter about internally resisted relays too as resistors work in either direction.

so any idea on how to fix this up? i certainly dont want the fusable links smoking once the fans turn on...

Point · Post by **Point** » Mon Jan 18, 2010 9:49 am

true about the resistor thing, but as steptoe was saying it may be a DIODE protected relay. diodes conduct in one direction only, and if you connect it backwards it will act as a dead short between + and - .

twilightprotege · Post by **twilightprotege** » Mon Jan 18, 2010 10:58 am

will give that a try and see what happens

twilightprotege · Post by **twilightprotege** » Mon Jan 18, 2010 7:43 pm

definately not a relay problem and i couldnt work it out. so i've gone back to a stock-style setup. 1 fan running off the stock fan wires, the other fan running off a relay switched by the first fan

YouTube · Post by **El_Freddo** » Tue Feb 16, 2010 4:32 pm

twilightprotege wrote:definately not a relay problem and i couldnt work it out. so i've gone back to a stock-style setup. 1 fan running off the stock fan wires, the other fan running off a relay switched by the first fan

This is how I've done my thermo fan setup, works a treat:

The On/off/Auto switch is used for when I want the fans on or Auto for when I'm generally cruising around. The off position is for the odd occasion when I'm crossing water - don't want to have the thermo fan trying to chomp through the radiator as it starts sucking on water rather than air...

Hope this helps. You should be able to wire in the two thermos the same - either off a larger relay if needed or with two horn relays.

Cheers

Bennie