tomperkins Posted June 15, 2014 Share Posted June 15, 2014 Hi there, I'm looking to wire in a cooling fan override switch as described in this thread (http://www.blatchat.com/t.asp?Id=61905). Sadly the links to a guide and diagrams no longer work. Anyone got a guide or diagram they could point me to please? Thanks, Tom Link to comment Share on other sites More sharing options...
Myles Posted June 15, 2014 Share Posted June 15, 2014 The original Chris W articles are still on my site http://alcester-racing-sevens.com/chris_w_-_electrickery.htm - as is a write up of how I find it (somewhere). The switches & relays edition is what you wasn't. Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 15, 2014 Share Posted June 15, 2014 Do you overheat regularly ? What engine and what form does the misbehaviour take ? Don't just mask what may be a fixable problem ! Link to comment Share on other sites More sharing options...
Myles Posted June 15, 2014 Share Posted June 15, 2014 It was certainly a sensible precaution for me - we've seen some fairly horrific temps over the years on tour on the Continent - it's reassuring in traffic! Link to comment Share on other sites More sharing options...
Bricol Posted June 15, 2014 Share Posted June 15, 2014 Surely making sure your overall cooling system is working correctly and the thermostat and thermostatic switch work properly is a better idea? Standard fan switching system on mine has worked well over the last 13yrs, including a couple of list tours in horribly high temps. Have you fitted an over-ride switch to your tin-top / everyday car? Same sort of cooling system, and I bet it sees more work/extremes of temperature? I have to admit to being a tight wad and not fitting a thermostatic switch in my Dutton trials car cooling system, relying on a manually operated fan - and its been forgotten a couple of times in the heat of the moment. Bri Link to comment Share on other sites More sharing options...
RS2000 Posted June 15, 2014 Share Posted June 15, 2014 Right at the bottom of Myles' page here Also check the connections on the switch at the radiator, mine had corroded and made intermittent contact meaning sometime the fan kicked in and sometimes it didn't Link to comment Share on other sites More sharing options...
tomperkins Posted June 15, 2014 Author Share Posted June 15, 2014 Quoting RS2000: Right at the bottom of Myles' page here Also check the connections on the switch at the radiator, mine had corroded and made intermittent contact meaning sometime the fan kicked in and sometimes it didn't Thanks for everyone's input. The reason for adding one is to offer a manual override until I can find the real problem (couldn't stand to stop driving the car as I love it). RS2000, you make a very good point. The problem is that sometimes the fan kicks in and sometimes it doesn't. It could well be corrosion is the issue as when I disconnected the wires from the rad switch and tried to touch them together to test the fan, it was quite hit and miss as to whether I made a connection or not. Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 15, 2014 Share Posted June 15, 2014 Also .... a new fan switch is cheap. Get things working properly first. If a k-series ..... do the cooling system mod from LF article in September 2012 ... I have a pdf version if you want it e.mailed. Change thermostat from std 88C to 82C Link to comment Share on other sites More sharing options...
tomperkins Posted June 15, 2014 Author Share Posted June 15, 2014 Quoting Myles: The original Chris W articles are still on my site http://alcester-racing-sevens.com/chris_w_-_electrickery.htm - as is a write up of how I find it (somewhere). The switches & relays edition is what you wasn't. Thanks Myles, I've just mocked that up using a relay and a switch that I have that has a built in LED. It seems to be working (the switch activates the fan) but there's one strange thing... The LED is ON when the switch is OFF and the LED then goes OFF when the switch is ON. I'm using piggyback connectors on the rad switch, then wiring the relay as shown in your diagram. From there I'm connecting terminal 86 on the relay to the ON terminal on the switch. The switch then has an OFF terminal that I'm wiring to ground and also a ground terminal on the side that I'm also wiring to ground. Please excuse me if my description is not the best, I'm not an expert when it comes to electrics. Any ideas on how to get the light behaving correctly? Link to comment Share on other sites More sharing options...
tomperkins Posted June 15, 2014 Author Share Posted June 15, 2014 Quoting SM25T: Also .... a new fan switch is cheap. Get things working properly first. If a k-series ..... do the cooling system mod from LF article in September 2012 ... I have a pdf version if you want it e.mailed. Change thermostat from std 88C to 82C It is indeed a K series. A PDF would be much appreciated, email is hello[at]tomperkins[dot]me Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 15, 2014 Share Posted June 15, 2014 Ok ..... Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 15, 2014 Member Share Posted June 15, 2014 Quoting tomperkins: I've just mocked that up using a relay and a switch that I have that has a built in LED. It seems to be working (the switch activates the fan) but there's one strange thing... The LED is ON when the switch is OFF and the LED then goes OFF when the switch is ON. I'm using piggyback connectors on the rad switch, then wiring the relay as shown in your diagram. From there I'm connecting terminal 86 on the relay to the ON terminal on the switch. The switch then has an OFF terminal that I'm wiring to ground and also a ground terminal on the side that I'm also wiring to ground.1 Disconnect the LED, then measure voltage to earth on terminal 87 with the override switch open and closed. 2 Your switch sounds more complicated than is needed. That circuit only needs a switch with two terminals. (Single-pole single-throw.) You can probably make the switch you have do that but you'll only use two terminals. Jonathan Edited by - Jonathan Kay on 15 Jun 2014 19:28:23 Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted June 15, 2014 Share Posted June 15, 2014 Info sent Link to comment Share on other sites More sharing options...
Myles Posted June 15, 2014 Share Posted June 15, 2014 Sm25t - I agree - better to treat the cause than the symptoms if you can. My Westie BEC (Honda Blackbird) is the most perfectly-behaving 7 I know. I'm not tempted to fit an override switch to it. My k-series is a different kettle of fish. The triple-pass rad I had (and have, if anyone wants one!) was useless - I get much better behaviour with a standard Ali-rad but I've had some dreadful behaviour in the past. Chucking a few hundred quid at a new rad or fan or pressure-based system is all very well - but if you've only got a marginal issue, chucking a switch and relay at the problem (giving you perhaps a minute or two of advance-cooling) is perhaps not such a daft idea. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted June 15, 2014 Share Posted June 15, 2014 I got through several thermostatic fan switches until I added a relay and haven't replaced one since. The motor start up/switch off surge causes the contacts to arc and eventually they become unreliable and then fail completely. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 15, 2014 Member Share Posted June 15, 2014 *arrowup*When I looked at Myles' circuit I thought about using the single relay for both ways of activating the fan. Is there any disadvantage to that? Jonathan Link to comment Share on other sites More sharing options...
Paul Deslandes Posted June 15, 2014 Share Posted June 15, 2014 Jonathan none that I can think of. Paul Link to comment Share on other sites More sharing options...
Martin S. Posted June 15, 2014 Share Posted June 15, 2014 I'm pretty sure my 7 (1994) doesn't have a fan relay, i.e. the rad switch is just in series with the pos power feed to the fan. As my car doesn't have an interior heater/fan any more (why would you want a heater in a 7?!) I simply wired the now spare interior heater fan switch in parallel (across) the rad switch. A relay would be better to reduce volt drop but as a quick fix it works well. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 15, 2014 Member Share Posted June 15, 2014 Thanks, Paul Jonathan Link to comment Share on other sites More sharing options...
glasgow Posted June 15, 2014 Share Posted June 15, 2014 There is a small error in the diagram ...... here Ahmed Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 15, 2014 Member Share Posted June 15, 2014 *arrowup*Thanks 1 My memory needs a relay 2 We all need that technical wiki... Jonathan Link to comment Share on other sites More sharing options...
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