JST Posted October 15, 2005 Share Posted October 15, 2005 i admit i am an electrics biff. i tried wirin up the two electic fans on the motor today. the aim being having. Off, two fans on, 1 fan on thermstatically controlled. via 3 way switch. originally both fans came on from one switch and this worked fine with a 30A fuse. i rewired the supply (direct from battery) to relay and then relay to each fan individually with 1 =ve wore for each fan and an earth for each fan. it then would not work without blowing a fuse. connecting it straight up they both come on and faster than before with the original smaller wiring. if i dosconnect the fans the wiring all works ok, and fuse not blown (no load). the twin on works as does the thermostatically controlled option. that is 12v out of both wires (one for each fan) for twin on and 12v out of the one wire (once engine is hot enough) for the thermo controlled wire. therefore i am confident that 3 way switch, two relays and thermo are fine. if i run it as a simple switch on/off, to relay and one or both fans it blows the fuse as well. both fans and relays have same earthing point. only thing i have noticed is that the rad doesnt have continuity with the vehicle body, could this be a problem>? shoudl i run an extra earth to it? any ideas. Quote Link to comment Share on other sites More sharing options...
siggy Posted October 15, 2005 Share Posted October 15, 2005 Do you need relay 2 as the thrmostat control unit is a relay put a meter in current remove fuse and place probes each side of the fuse and measure what the current is with both fans operating Quote Link to comment Share on other sites More sharing options...
Neil Marshall Posted October 15, 2005 Share Posted October 15, 2005 James A simple two wire thermostat should sit between the second relay and earth - ie it triggers the relay on the earth side - and the switched positive supply should be connected to fan 2; see amended diagram below. You've just got the thermostat on the wrong side of the relay, an easy mistake to make. If you're using a three wire electronic thermostat [eg a Revotec controller] then the third wire goes direct from the fuse to the controller. Hope this helps - tell us how you get on. Neil Quote Link to comment Share on other sites More sharing options...
siggy Posted October 15, 2005 Share Posted October 15, 2005 you could utilise both contacts i.e. N/C (relay de-energised) through thermostat to one fan. N/O relay energised with switch on both fans running.? Relay 1scrap that stupid idea have you got the correct wires on the correct terminal? easily done! Quote Link to comment Share on other sites More sharing options...
siggy Posted October 15, 2005 Share Posted October 15, 2005 neil that negates the need for the thermostat? Quote Link to comment Share on other sites More sharing options...
siggy Posted October 15, 2005 Share Posted October 15, 2005 Quote Link to comment Share on other sites More sharing options...
Neil Marshall Posted October 15, 2005 Share Posted October 15, 2005 neil that negates the need for the thermostat? No, the thermostat should act as a simple switch for the relay when in the 'B' position as per the original circuit diagram. The diode between the two fans would only be needed if you wished Fan 2 only to come on under control of the thermostat - thinking about it, that's quite an elegant option as you wouldn't need two fans on for normal on-road use.. Are you referring to a three wire controller? The third wire is to power the controller's internal circuitry, not the switched power. Neil Quote Link to comment Share on other sites More sharing options...
siggy Posted October 15, 2005 Share Posted October 15, 2005 So you have a relay operating a relay might as well just remove relay 2 and use thermostat as the relay IIRC when I installed my electric fans on my last 90 I used the switch (two way) as on or auto and when the switch was in auto the thermostat turned on and off the fans via the temp sensor in the rad. When the switch was on then the wiring strapped out the thermostat and put the power straight onto the fans Quote Link to comment Share on other sites More sharing options...
Neil Marshall Posted October 15, 2005 Share Posted October 15, 2005 So you have a relay operating a relaymight as well just remove relay 2 and use thermostat as the relay IIRC when I installed my electric fans on my last 90 I used the switch (two way) as on or auto and when the switch was in auto the thermostat turned on and off the fans via the temp sensor in the rad. When the switch was on then the wiring strapped out the thermostat and put the power straight onto the fans Siggy, a simple thermostat is just an inline bi-metalic strip switch, not a relay. I accept that, in principle, you could ditch the relay but in practice you would run the risk of burning out the bi-metalic strip as all the current to the fans would be running through it and it would pit thru arcing as it flipped constantly on and off. I like the diode idea, though. Elegant. I think James should consider it. Neil Quote Link to comment Share on other sites More sharing options...
siggy Posted October 15, 2005 Share Posted October 15, 2005 Erm possibly!! the thermostat that I fitted on my 90 was a relay with the switching controlled by the temp sensor inserted in the rad. Pity I don't have the drawings to hand as I could show you the kenlowe paper work for fitting.......... Quote Link to comment Share on other sites More sharing options...
Neil Marshall Posted October 15, 2005 Share Posted October 15, 2005 We have exactly the same approach below as James' diagram - the thermostat should act as a switch for the relay [older Kenlowe instructions] - but best to switch on the earth side. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted October 15, 2005 Share Posted October 15, 2005 Scrap the circuit and start from scratch 1) Use a sidelight/headlight switch instead of the centre off. 2) Connect the 'common' of the switch to the stat. 3) Connect the other side of the stat to earth 4) Connect one side of each relay coil to +ve (ign or whatever) 5) Connect the other side of one relay coil to the 'sidelights' connection 6) Connect the other side of the other relay coil to the 'headlights' connection. 7) Connect one side each of the contacts to the battery via its own fuse as close to the batt as poss 8) The remaining contacts on the relay are taken one to each fan Switching to 'sidelights' puts one fan on, 'headlights' both, if the stat is closed. You could have variations on the theme, eg put the stat in series with one of the relay coils so one fan is automatically controlled, the other manually and so on....... Quote Link to comment Share on other sites More sharing options...
siggy Posted October 15, 2005 Share Posted October 15, 2005 Aha I see the main difference being the positions of the relays in the circuit but can see that, that does not necessarily matter Quote Link to comment Share on other sites More sharing options...
Neil Marshall Posted October 15, 2005 Share Posted October 15, 2005 Scrap the circuit and start from scratch.....Switching to 'sidelights' puts one fan on, 'headlights' both, if the stat is closed. You could have variations on the theme, eg put the stat in series with one of the relay coils so one fan is automatically controlled, the other manually and so on....... We have the 'stat in series with one of the relay coils' in the amendment to James' circuit....and as Siggy has suggested, adding a simple diode will control whether one or two fans operate. I guess for competition use of a three way dial switch might be preferable to a side/main beam switch. But, as ever.....many ways to skin a cat!! Quote Link to comment Share on other sites More sharing options...
siggy Posted October 15, 2005 Share Posted October 15, 2005 I think you need it otherwise you'll end up running both fans all the time purple is with the switch on running both fans green would be switch in auto and only one fan meant to be running (but two would) brown diode would block second fan (diode only allows current in one direction) obviously on neils diagram Quote Link to comment Share on other sites More sharing options...
JST Posted October 16, 2005 Author Share Posted October 16, 2005 guys, thanks for all the input, think ihave amanged to follow most. after experimenting i have found the fault with the original diagram. well not the diagram but the putting it together , there was a short across on of the motors which resulted in the fuses blowing. sorted that so it now works as per the original diagram. switch B is thermo controlled x1 fan but the other one comes on as well due to wiring setup of option for switch 2. so another relay (3rd!) has been added to to the both fans on option. switch A is both fans. which means once selected it switches two relays one for each fan. - this works OK. switch B no does a single fan. the problem running two wires one to each fan from the same relay meant that when switch 1 was used and the fan engergised, the 12v when back up the wire to the constant on relay 1 then engergised ythe other fan. so ihave just used another relay in leu of your suggest diode as i dont have one. thank for the tips. original fault being earthing, they always say earths are 90% of faults! Quote Link to comment Share on other sites More sharing options...
siggy Posted October 16, 2005 Share Posted October 16, 2005 remove third relay and stick a diode in as it only allows current flow in one dirction you can get them online or a your local maplins? Quote Link to comment Share on other sites More sharing options...
landi41 Posted October 16, 2005 Share Posted October 16, 2005 guys,thanks for all the input, think ihave amanged to follow most. after experimenting i have found the fault with the original diagram. well not the diagram but the putting it together , there was a short across on of the motors which resulted in the fuses blowing. sorted that so it now works as per the original diagram. switch B is thermo controlled x1 fan but the other one comes on as well due to wiring setup of option for switch 2. so another relay (3rd!) has been added to to the both fans on option. switch A is both fans. which means once selected it switches two relays one for each fan. - this works OK. switch B no does a single fan. the problem running two wires one to each fan from the same relay meant that when switch 1 was used and the fan engergised, the 12v when back up the wire to the constant on relay 1 then engergised ythe other fan. so ihave just used another relay in leu of your suggest diode as i dont have one. thank for the tips. original fault being earthing, they always say earths are 90% of faults! One of the more interesting discussions of late................. I knew all along you needed a 3rd relay or a diode :) I just thought seeing the lads were putting you on the right track, that you would work it out :) Quote Link to comment Share on other sites More sharing options...
JST Posted October 16, 2005 Author Share Posted October 16, 2005 well its all in and working now, i didnt have diodes to hand so resorted to 3rd realy in the end. heres my complete circuit diagram. total cost £80....... (£60 was the PACET thermostat) decent bit of kit though and a very good way of connecting the sensor into the top hose (hence the reason i went for it). Veh wiring supplie dthe swithces etc. amazing how it quickly adds up......... Quote Link to comment Share on other sites More sharing options...
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