wardy18 33 1 Cars Posted March 28, 2008 right so im rubbish with electrics so i need some advice!! my race 205 had some silly little fans on the rad which did nothin as she overheated at the hilllcimb monday so as i had a set of standard 205 fans i have re-fitted these but have cut down the plastic cowling to the bare bones so to save weight currently it has 2 fans in so im not sure whether to keep both or just run one of teh fans and remove the other one........what you think!?!? also as its on a manual switch i assume this switch isnt gonna be powerful enough to hold the amps needed for the fans and ill just end up burnin out the switch, so in comes relays, but how do i fit in a relay to the circuit, if i need one................please advise?! thanx simon Share this post Link to post Share on other sites
DrSarty 90 1 Cars Posted March 28, 2008 (edited) Hi Simon, relays are interesting and quite simple things relay....I mean really. Have a wander through here: click and have a look at the relays in turn down below. You are right in that a basic switch on the dash won't stand the current drawn by a fan and other high current circuits. For your cooling fan you should have a simple 'usually open - 4 pin relay' (see the Hella site), where pins 85 & 86 are your low current side. Either one of those pins should have a switched live going in to it (i.e. live when the ignition is on) and earth the other side THAT IS INTERUPTED by your dash switch, i.e. flicking the dash fan switch makes the earth circuit. When this happens, it closes the relay circuit allowing your thicker, high current wires attached to pins 30 & 87 (again - order doesn't matter) to carry power from the battery positive terminal (e.g. batt to pin 30) onwards to the fan positive terminal (from the other pin 87 on the relay). There's a circuit diagram of the whole cooling fan set-up in my project thread, including the OE set-up (incl resistor for slow fan speed), the rad switch, a manual dash switch AND an ECU controlled back up. I did this belt and braces approach using separate circuits such that if the OE system failed, the back-ups could still operate. I think this'll take you to my diagram: http://forum.205gtidrivers.com/index.php?a...ost&id=4117 HTH Edited March 28, 2008 by DrSarty Share this post Link to post Share on other sites
tom_m 0 Posted March 28, 2008 that's not strictly true. if you use components that are high enough rated there is no reason to use a relay. mine was fine on a simple switch arrangement for a year without melting, or burning out. Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 ok sound, ill have to check the set up at the moment as all thats fitted is the switch direct to these mini fans so the switch itself should already have the live and earth etc, ill need to draw up a diagram as im still not sure how ther all go!! so the switch - live from batt + earth relay - live from batt + earth on bigger guage wire is thats right?! sorry im useless at wiring which is why im glad i have carbs fitted hehe Share this post Link to post Share on other sites
DrSarty 90 1 Cars Posted March 28, 2008 that's not strictly true. if you use components that are high enough rated there is no reason to use a relay. mine was fine on a simple switch arrangement for a year without melting, or burning out. Yes, as long as you check the rating on the switch you buy; more current handling = more cost. An auto factor cheapy (and small switch) will cost around £2 as a guideline. Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 ill check the ratin of the switch at lunch, i assume it'll be printed on it somewhere!! Share this post Link to post Share on other sites
DrSarty 90 1 Cars Posted March 28, 2008 (edited) ok sound, ill have to check the set up at the moment as all thats fitted is the switch direct to these mini fans so the switch itself should already have the live and earth etc, ill need to draw up a diagram as im still not sure how ther all go!! so the switch - live from batt + earth relay - live from batt + earth on bigger guage wire is thats right?! sorry im useless at wiring which is why im glad i have carbs fitted hehe No my man, stop. A switch purely is like a break in a line. Your switch only needs one positive or negative input; not both. You normally operate switches on the negative side, so a non-illuminated switch (which does need a small positive feed just to make the bulb/LED glow) should only have one pin going straight to earth, and the other side goes to either: the earth of the item you're turning on/off (if the switch can handle the current), OR it goes to pin 85/86 of the relay. Available for any more help; don't want you zapping yourself or having an engine fire through burnt out wires. Here's another effort at a diagram for you: Edited March 28, 2008 by DrSarty Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 so somethin like this, would prefer not to start fartin around with ignition wires, be easier to take them straight from batt!! amend diagram to correct if its wrong thanx alot mate Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 ooh yours looks more professional than mine lol so the switched live can i just run this from the batt or does it have to be from ignition?! Share this post Link to post Share on other sites
DrSarty 90 1 Cars Posted March 28, 2008 ooh yours looks more professional than mine lol so the switched live can i just run this from the batt or does it have to be from ignition?! Your diagram is fine, just a little stylized. Your diagram will work fine, with just two points I ought to make. You don't need a thick wire for the positive feed to pin 85/86, and taking it from the battery does mean that you can operate your fan even with the engine off. The risk you run here, is that you could walk away from the car, leave it on and run your battery flat; that's why I suggest a switched live. Even your stereo or cigarette lighter will probably have a switched ignition live, i.e. only on when the key is turned to position 1 or more. Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 yeh im good with stereos but seein as i have no wiring at all bacause of the carbs the wiring loom is completely gone and a bespoke ignition wiring is in place along with facet pump and starter and thats all the wiring i have so ill just rig it up straight from the batt so i can cool it even when it turned off, i have a jumper battery that plugs in with a jump plug so no worries!! thanx for your help mate i might have an old relay from past 205's ive stripped so i could use one of those if the switch isnt rated high enough, what rating will the switch need for one 205 fan? Share this post Link to post Share on other sites
DrSarty 90 1 Cars Posted March 28, 2008 My 12" Pacet cooling fan is rated at 11amps, so I'd guess a 20A relay or switch would be just fine. If you have an old relay, 6 bucks and my right nut says it will be 20A, and this will be printed on the top/front along with a pin diagram. Good luck. Rich Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 fine job well hopefully the switch is be rated high enough that i dont need one but ill check in a couple hours!! how much are those facet fans, would be mush lighter that the 205 cowling with a standard 205 fan in like ill be running!! Share this post Link to post Share on other sites
tom_m 0 Posted March 28, 2008 as standard the cooling fan is on a 30A fuse, so you might want to change that if you're still using the same point from the shunt to power it Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 err yeh i suppose if im running it straght from the batt i better mate sure i put a fuse in it, or ill wire the live in with the circuit that the cut off switch is on which is also fused in the main switch box Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 switch on the right is the fan switch Share this post Link to post Share on other sites
Rob_the_Sparky 9 Posted March 28, 2008 FYI a stock GTi only uses one fan, dual fan set-ups are from a diesel but a second fan won't do any harm. Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 im only gonna run one thou to keep the weight down, but with it bein a race engine and havin a much higher CR ive always got that option of fittin the second one back in!! Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted March 28, 2008 (edited) im gonna have to go down tehr elay route i think, the switch in the car already is wired into the ignition switch so the switch isnt in the negative line, its in the positive, so all i need to do is the wire thats already run from the switch connects to the switched live (85 or 86 on the relay) then run an earth from the other (85 or 86) then wire in the fan to the relay as per diagram Edited March 28, 2008 by wardy18 Share this post Link to post Share on other sites
wardy18 33 1 Cars Posted April 1, 2008 set it all up last nite, and works a treat with the relay in thanx for the help Share this post Link to post Share on other sites
