dazzle740

iTrader: (1)

Hi there people
Just a general inquiry, i want to rewire the fans on saph but just so i can confirm the idea of how the fans are activated does anyone have a form of wiring diagram for the fan circuit, plus has anyone else does this mod to their cars to by-pass the fuse box if so what size fuse and relays did they use.
Iknow that in the fuse box it uses a 30 Amp fuse but that is for both fans is it still the same for each fan seperatly?

NEEDFORSPEED

hi bud basically the fan switch has an earth one side, the other side goes to the relay in the fuse box. the fans have an earth at them and the relay puts a live to them when switched. a 30a or 40a relay and a 30a fuse will be fine. and a bit of nice overbraid and heatshrink wouldnt hurt either lol

dazzle740

iTrader: (1)

Cheers for that but i was gonna run power to each fan seperately but both swicthed by the fan/rad temp switch do i still need to use 30Amp relay and fuses
P.S. hows the car comin along close to being finished yet?

foreigneRS

see your post in GD also.

why do you want to wire the fans individually? what's the advantage?

dazzle740

iTrader: (1)

no perticular reason it is just the way i have seen them done on other cars and when speaking to a guy i know how makes the looms up says thats the way he always makes them so i suppose there must be reason.

AndyPen

iTrader: (24)

Reason is the surge of amperage when both fans hit at the same time, especially when they are worn with age and draw more current then normal. Thats when fuses blow and the fuse box eventually melts.

Wiring them to start independantly means only one at a time surges the current and all is safe - most folks would add a new fuse ( and maybe relay) for each one as well - so at least one fan works if a fuse blows.

Hope this helps,

Andy

foreigneRS

not really andy

as far as i can tell from what dazzle740 has said, they will be wired from the same switch (the only one that is at the bottom of the rad) and the same relay so they will still both switch on at the same time and draw the same current

usually you wire them separately so that you have the option of having them in series to get 6v each and run at half speed, or in paralel where they both get 12v and run at full speed.

that kind of strategy used to be common on A/C condenser fans (low speed when A/C on to aid condensing, and then full speed when a high pressure switch was reached to bring the pressure down), until PWM control came in where the duty cycle is variable between 0 and 100% to control the speed to whatever you want

AndyPen

iTrader: (24)

a couple of cars around here have had burnt out fuse boxes (well one is just a bit distorted) so they've wired them to be independantly wired / controlled - but both have seperate relays fired by the switch on the rad wires - power comes from direct from battery wires with independant fuses for each relay. Works a treat, especially if one is on a slight delay (if I recall correctly that came from an xr4x4??). I can check if you wish?

If you ask at Lucas specialists it was the fix they offered Fords from way back. I have some paperwork here if you are interested? One dealership for example had all their cars done to save hassle from owners who were frequently replacing fuses.

One guy at Donnington also has an overide switch on top of the dash for all that for those hot show days. You can buy the set up on one of the ebay stores apparently. Not spotted it myself though.

Makes sense doesn't it?

foreigneRS

if they're from separate relays and fuses then it makes sense

dazzle740

iTrader: (1)

sorry if was'nt clear
yeah both fans will have seperate fuses and relays but they will be switched on by the same switch

TurboShed

My fans are a perennial problem, and my fusebox is a mess, but if I could be bothered, this thread has all the answers

AndyPen

iTrader: (24)

Well I've seen them wired up neatly and it only took the guy around an hour or so to do... I'm gonna get all the bits for my 500 soon )

foreigneRS

do it, before they no longer work and you overheat the engine and lose the head. as said, it needn't take long and doesn't cost much

Garsy™

i did mine but i wired them both to 1 single switch. all i did was take all the original wiring out, replced it all with new wires, relay, temp sender and fuse then spliced a wire into them where they meet the fan. i then ran that wire to a 30a relay and then to a switch on the centre console. i then wired that to a 30a inline fuse which then continues to the live on the battery. never had any problems but then again i very rarely use the switch lol hope this is of some help mate.

p.s mine still kick in off the standard wiring and sender with no problems

tabetha

I used the std temp switch and used this to trip the relay NEGATIVELY so that it runs on after switch off if necessary as engines get hotter(water) after switch off.
Im then put in and overide switch in case of temp switch failure so it could be switched MANUALLY, this of course has to trip NEGATIVELY so used another relay but fed it with NEGATIVE instead of POSITIVE through the LOAD terminals, this only remains LIVE while ignition is on so fans CANNOT BE LEFT ON.
tabetha

dazzle740

iTrader: (1)

if anyone wants to know where to get the bits from a good place is www.vehiclewiringproducts.co.uk but obviously there will be many other places

tabetha

I get stuff from them, excellent service and prices.
Another good one is POLEVOLT.CO.UK
tabetha