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Wiring for electric fan with override switch


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Ok had a look at previous posts and cant see the answer. I have a TR6 and am adding an electric fan (the past few hot days have allowed the temp to get 3/4 along gauge without sitting in a jam...). So am planning to use a relay and have an override switch (just in case). There is a thermo switch fitted to the stainless bottom hose. My question is ...whats the best way to wire the fan :-

 

  1. is it best from a permanent live or should it be switched via ignition
  2. how to fit the override switch ie how to wire it

I had planned to run the fan from a permanent live to the thermo switch then to +ve on the fan:-

and the override via the relay direct to the +ve side of the fan:-

 

 

Not convinced this is best so wondered what others have done.

 

Any ideas appreciated, thanks

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It's normally unlikely to happen but I would avoid a direct battery feed as the fan can then continue running after you have switched or even start spontaneously on a very hot day ( as in those recently experienced) leading to a depleted battery. Go via the ignition fused circuit.

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I have mine permanently live (fused naturally) deliberately so as to avoid heat soak problems when shutting down, at least in theory and it seems to work fine. The weather would have to get pretty hot to trigger the thermoswitch without the engine running. We don't have many 80 degree Centigrade days around here.

Edited by peejay4A
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Thanks chaps, I'm on the case. Had the Revotec kit before on an earlier car, got it at the NEC for £100, now however price has rocketed I'll buy a 14ins fan (flebay £20) , fabricate some brackets a la Revotec and fit and do wiring as directed here, will be quids in.

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Hi Robin, My TR6 has a Kenlowe, fitted by a PO; Every electric fan I've fitted to cars(including my current A35) has come from my local scrapyard; most cost effective, enviromentally sound & satisfying!!! All the best, Paul.

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Hi Neil,

I think what Alan is pointing out is that you have one side of the override switch going to earth. In the non-override position and with the thermoswitch closed you will be shorting your fused supply direct to earth through the override switch.

 

Simply disconnect the earth wire from the switch and use the switch as a simple on/off toggle.

 

Roger

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Years ago the electric fan on my 6 started blowing fuses on cut-in. so I fitted a double feed via 2 independant circuits, one via ignition and one direct feed, both fused and relay equipped. for that I added a 2nd fusebox fed by 2 circuits. It was a rather complex system and I don't remember how I did it, age related. But it works now for about 8 years, hope it stays like that.

 

In the mean time I have replaced the problem fan.

 

The most simple way in fact is to switch the fan by hand and to forget about the thermo switch, as an old practice I do that anyway as soon as a potential overheating situation sticks it's head up

Edited by jean
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Years ago the electric fan on my 6 started blowing fuses on cut-in. so I fitted a double feed via 2 independant circuits, one via ignition and one direct feed, both fused and relay equipped. for that I added a 2nd fusebox fed by 2 circuits. It was a rather complex system and I don't remember how I did it, age related. But it works now for about 8 years, hope it stays like that.In the mean time I have replaced the problem fan.The most simple way in fact is to switch the fan by hand and to forget about the thermo switch, as an old practice I do that anyway as soon as a potential overheating situation sticks it's head up

I agree, Jean. I figure a thermo switch is another place for coolant to leak from!

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Time passes and new ideas arise.

 

In the end my own system is quite different to that I suggested in the previous thread, but mainly for the same reason as noted - switching earths doesn't allow the LED in the switch to illuminate.

 

TT

 

This stupid editor does not allow me to drag and drop images into the editing space, despite me trying four different image formats, so much for 21st century technology!

 

 

So much as I'd like to share my suggested solution. it is stuck on my 21st century MAC awaiting a revolution in forum technology!

 

If anyone is interested send me an email and I'll send you a reply with an attached image.

 

TT

Edited by tthomson
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Tony, have sent you a pm

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When I upgraded mine from a standard 13" Kenlowe to a 14" dual speed Kenlowe I reconfigured the supply from the direct to via the ignition switch. The previous fan would sometimes run on for over 10 minutes when the engine was turned off :angry:, not good for the health of the battery <_< and providing little benefit in my opinion.

 

I haven't used the additional feature of the override, I want it all automatic like my daily driver. The fan is set to come on just above normal operating temperature to keep the water temperature as consistent as possible (which is a fraction over 1/2 way on the temperature gauge). It generally only comes on for a short while when slow moving traffic or crawling up hill in hot weather. :)

 

What I will most likely do in the future is fit a relay to disable the fan supply whilst the engine is cranking (just incase the fan should become enabled at the same time) and have the radiator modified to accept a duplex temperature probe and configure one of the outputs as a high temperature alarm.....it's added to the winter wish list :rolleyes:

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My fan is connected via a temp sensor switch fitted into the radiator to the battery. It cools everything down beautifully after I switch off, I've had no problems with it at all.

 

Cheers

 

Tony

Edited by Tony Millward
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