need4speed Posted May 11, 2015 Share Posted May 11, 2015 Been thinking about how I'm going to control my cooling fans. I would like to control them via my MS ECU but for the life of me I can't remember whether or not I specified with Nige to add this feature to my board. Wondered if someone could tell from the pic below if I need to have it modified or not. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 11, 2015 Share Posted May 11, 2015 Nope, you would have a transistor, resistor and a diode in the proto area if you had, assuming they are being done the same way as they always were. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 12, 2015 Share Posted May 12, 2015 Or in Q23 if someone's being very cunning Quote Link to comment Share on other sites More sharing options...
need4speed Posted May 12, 2015 Author Share Posted May 12, 2015 Ok. So on the advice of Nige himself I'm going to use something else to switch the fans. Probably an X-fan.. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 12, 2015 Share Posted May 12, 2015 Ehm, love to know the reasons behind that Quote Link to comment Share on other sites More sharing options...
need4speed Posted May 12, 2015 Author Share Posted May 12, 2015 He wasn't saying DONT do it. He was just advising not to. Fans draw large currents, and when they short / back feed, there will / can be a LOT of amps hunting for a earth - and a PCB board is a bad one ! Quote Link to comment Share on other sites More sharing options...
robertspark Posted May 12, 2015 Share Posted May 12, 2015 ....surely you use the transistor to then switch a relay...? Not feed the fan directly from the pcb The fan can then be fused (correctly) and the ms can be seperatly fused (plus with the addition of the diode protected from reverse emf when the relay coil de-energises Guess you want the ms to switch the fan on and off at the correct temp? Rob Quote Link to comment Share on other sites More sharing options...
need4speed Posted May 12, 2015 Author Share Posted May 12, 2015 Yeah but maybe it doesn't quite work like that when you have followed the standard MS wiring diagrams? Not sure. Either way, if that's what Nige recommends that's what I'll go with Quote Link to comment Share on other sites More sharing options...
elbekko Posted May 12, 2015 Share Posted May 12, 2015 All the MS should be doing is pulling a relay switching current to ground... not exactly groundbreaking. Quote Link to comment Share on other sites More sharing options...
robertspark Posted May 12, 2015 Share Posted May 12, 2015 not trying to disuade anyone from doing anything (or HfH's knowledge), but just clarify that you should not be driving the fan directly. Here's an example (yes not V8, just the principle), top LHS corner "fan", below the title... one way to do the external side http://www.mkosonen.com/mattsmswiring.gif Circuit board side, same principle as this, but instead of "pump" it will be "fan". http://msextra.com/doc/ms1extra/MS_Extra_Hardware_Manual_files/water-circuit.jpg The negative thing is you will loose an output pin....unless you had one spare that is. Rob Quote Link to comment Share on other sites More sharing options...
need4speed Posted May 12, 2015 Author Share Posted May 12, 2015 Maybe Nige will chime in. I'm maybe not explaining it right. I'm not great with vehicle electrics so it's not surprising..... Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 12, 2015 Share Posted May 12, 2015 Yep, no chance of back emf to the coil side of a relay -no chance of it getting back to ecu. Quote Link to comment Share on other sites More sharing options...
robertspark Posted May 12, 2015 Share Posted May 12, 2015 ... So what's the point of the diode? Is it not to prevent the spike from a collapsing field of the coil when the voltage is being removed? Not being a smart a. Just learning? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 12, 2015 Share Posted May 12, 2015 'to the coil side of the relay', as in from the fan motor. Quote Link to comment Share on other sites More sharing options...
robertspark Posted May 12, 2015 Share Posted May 12, 2015 Think I've just read your post again.... Purpose of the relay is more current load than any emf issue, the diode is there to protect the chips from spikes, could use a Darlington pair to perform a similar function but then the problem is the circuit board trace taking the current At the moment I've taken to using solid state relays these days when I can (smaller and faster than a traditional relay ).. Just watch the current rating http://m.ebay.co.uk/itm/121183847014?nav=SEARCH Quote Link to comment Share on other sites More sharing options...
need4speed Posted May 13, 2015 Author Share Posted May 13, 2015 I can only imagine that Nige has seen his fair share of damaged boards due to cooling fan issues. For what other reason would he strongly advise against it? Especially as I would be paying him money to modify my board for me.... Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 13, 2015 Share Posted May 13, 2015 I must say I don't really agree with Nige on this one, but then I'm not selling electronics to the general public with their inherent capacity to break absolutely anything I run twin fans from my MS, via relays of course, and it works lovely. Quote Link to comment Share on other sites More sharing options...
zardos Posted May 13, 2015 Share Posted May 13, 2015 Having the Fans independent of the ECU can be an advantage is some configurations.On one of my V8's I had the fans wired independent of the ignition switch, which meant they would continue to run after engine shutdown, to keep air moving over the block (and cool the water in the rad more). Which was useful for it's cooling and not so easy to do with ECU controlled fans. Quote Link to comment Share on other sites More sharing options...
need4speed Posted May 13, 2015 Author Share Posted May 13, 2015 ...but then I'm not selling electronics to the general public with their inherent capacity to break absolutely anything Just what are you implying here? Quote Link to comment Share on other sites More sharing options...
Dave W Posted May 13, 2015 Share Posted May 13, 2015 The control that MS gives you over the temperature at which the fan cuts in and out is far better and based on the temperature at the cylinder head rather than the temperature in the top or bottom hose. This is preferable to a top hose fitting and similar to a bottom hose fitting. Being able to adjust the hysteresis allows you to set a lower activation point than the "mechanical" switches/sensors with a fixed hysteresis where you have to set the turn on point high enough to avoid the turn off point dropping below the thermostat close point. There's absolutely no reason why you can't drive a relay (or two in my case) direct from the MS ECU to control the fans. I use a fan relay and fuse for each fan so I'm unlikely to lose both fans due to a fault in one. If you want the fans running when the engine isn't then you either turn the ignition on and don't start the engine or have a switch on the dash to operate the relays manually - I have this anyway on mine as I use an off/on/on switch in the MS control circuit for the relays to allow the fans to be turned off/auto/always on. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 13, 2015 Share Posted May 13, 2015 Sounds like Dave and I have the same setup, and Fridge very similar again, twin fans, twin relays, with separate fused feed for each, I have an off/on/on switch for 'normal' (MS controlled), 'off' for entering water, and 'on' for forcing both fans to run no matter what the temperature. No problem with this ever, except the relays seem at their limit and occasionally stick on, despite being 30A Bosch versions. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 13, 2015 Share Posted May 13, 2015 My setup switches the twin fans in series/parallel to give dual-speed, as originally designed by Bull Bar Cowboy. Uses 4 relays. Quote Link to comment Share on other sites More sharing options...
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