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Fan switch


zhap135
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An looking to fit an electric fan on the pinto. Was wondering whether to put the stat/switch inline with the coolant hose, or does anyone know whether it's possible to get a switch/sender combo that goes in the block where the standard sender goes?

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Where-ever you put the auto switch add an override switch in parallel & a tell tale light on the dash -- always good to be able to check function or bring in the fan sooner if a traffic jam looms. 

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6 hours ago, sylvia.fry2 said:

Where-ever you put the auto switch add an override switch in parallel & a tell tale light on the dash -- always good to be able to check function or bring in the fan sooner if a traffic jam looms. 

Good call thanks - a friend of mine did this in his capri, so will have a chat with him on wiring

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7 hours ago, rthomas69 said:

I've put mine in the coolant line. You can buy an aluminium hose fitting with a boss on it to accept a switch.

 

Yeah, CBS do something along those lines. The easiest think will to put it direct into teh block, I just don't know whether that's possible

 

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I had an incident where I turned on the override switch and the dash light came on but unknown to me the fan did not turn on.  Luckily it was cold day so I didn’t actually need it.  So make sure you wire it so it actually tests for the fan running and not just that the switch works.  My fan has a permanent 12V feed and a switchable earth and the 12V supply had failed. But the light had a separate 12V supply so came on when the earth switch was made.

You also need to decide if you want the fan to run on after the engine has stopped (This is what I have).  If so then it is a direct battery to fan feed.  If not then the 12V feed needs to come via the ignition switched 12V supply and will then probably have to operate via a relay.

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Posted (edited)
2 hours ago, alanrichey said:

I had an incident where I turned on the override switch and the dash light came on but unknown to me the fan did not turn on.  Luckily it was cold day so I didn’t actually need it.  So make sure you wire it so it actually tests for the fan running and not just that the switch works.  My fan has a permanent 12V feed and a switchable earth and the 12V supply had failed. But the light had a separate 12V supply so came on when the earth switch was made.

You also need to decide if you want the fan to run on after the engine has stopped (This is what I have).  If so then it is a direct battery to fan feed.  If not then the 12V feed needs to come via the ignition switched 12V supply and will then probably have to operate via a relay.

That's brilliant Alan. I see that by allowing the fan to continue after the engine stops will continue to cool the  radiator., however the coolant is no longer circulating, so the engine will still largely cool under it's own convection/radiation. What was the reason to keep the fan running?

Edited by zhap135
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That was how it was designed by the original owner 😄  You are right of course which is why some keen owners fit auxiliary electrically driven water pumps as well. to maintain circulation while the fan is running.   I have found by experience that it seems to cool off a bit quicker if the fan stays on for a bit even though it is only the radiator being cooled, but maybe I am imagining it.   So it's really personal choice, but if you go to a kit car meet and line up with the others you will find quite a few of them are gently humming to themselves long after the owner has left.

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Posted (edited)
2 hours ago, alanrichey said:

That was how it was designed by the original owner 😄  You are right of course which is why some keen owners fit auxiliary electrically driven water pumps as well. to maintain circulation while the fan is running.   I have found by experience that it seems to cool off a bit quicker if the fan stays on for a bit even though it is only the radiator being cooled, but maybe I am imagining it.   So it's really personal choice, but if you go to a kit car meet and line up with the others you will find quite a few of them are gently humming to themselves long after the owner has left.

Hmm, not sure I'm that keen, (for the electric water pump) but allowing over run of course is simply which terminal it's wired. I'm using a light battery, so would be just as well to make sure I'm not going to flatten it. 

Actually a really good point has occured to me. Is there a favoured place to mount the inline switch? rad infeed or out feed, top or bottom?

EDIT: I'm thinking it should be on the bottom/infeed as you want to regulate the temp going in, rather than run the fan based on the temp of the water coming out - is that right?

Edited by zhap135
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I would have to disagree with that I think.  The fan is there to prevent the engine overheating, so my logic would be that you want to be monitoring the hottest part of the system. Otherwise you could be getting cylinder head damage while the output from the bottom of the radiator is still within limits.  So I have my switch in the top hose.  However I have to admit that the original switch on the Superspec was built into the bottom of the radiator (it uses a rad from a Rover SD1), so maybe I’m talking rubbish 😀

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Wire fan supply to switched side of starter motor ( fan will get it's "earth" back though starter windings ) & fan will be cut out when cranking engine. ( will help a low power battery ) Wire tell tale light same "earth " & live feed on fan terminal.

On Florin at plus 55/60 mph the Fan becomes a poor generator & the tell tale on the dash glows if fan not powered.

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3 hours ago, alanrichey said:

I would have to disagree with that I think.  The fan is there to prevent the engine overheating, so my logic would be that you want to be monitoring the hottest part of the system. Otherwise you could be getting cylinder head damage while the output from the bottom of the radiator is still within limits.  So I have my switch in the top hose.  However I have to admit that the original switch on the Superspec was built into the bottom of the radiator (it uses a rad from a Rover SD1), so maybe I’m talking rubbish 😀

Yeah I see. Tthe temperature gauge from the block would be the one to indicate overheating, and of course you need to stop if that's the case

My logic is that if taken from the outfeed the water is always likely to be hot when the engine is at temp , so the fan will be always on (not a problem in itself but kind of negates the need for a thermostatic switch, and puts load on the engine perhaps unnecessarily.) 

On the other hand you want to know that if the water entering the engine hasn't at least been cooled sufficiently by the rad alone it gets a bit of help by turning the fan on.

That's my theory anyway, but I'd sooner test the theory to destruction that the block!😄

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I think you need to consider the operating temperature of the fan switch.

For arguments sake, if your thermostat opens at 88C and your fan switch (fitted to the bottom hose) operates at 95C, would you want to wait until the coolant leaving the radiator reaches 95C before the fan cuts in? What would the temperature of the coolant leaving the engine be at this time? If the fan switch is located in the top hose the fan will cut in when the coolant leaving the engine reaches 95C. When the engine is at normal running temperature the fan would not always be on because the coolant has not reached the switch operating temperature.

 

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2 hours ago, RedTrev said:

I think you need to consider the operating temperature of the fan switch.

For arguments sake, if your thermostat opens at 88C and your fan switch (fitted to the bottom hose) operates at 95C, would you want to wait until the coolant leaving the radiator reaches 95C before the fan cuts in? What would the temperature of the coolant leaving the engine be at this time? If the fan switch is located in the top hose the fan will cut in when the coolant leaving the engine reaches 95C. When the engine is at normal running temperature the fan would not always be on because the coolant has not reached the switch operating temperature.

 

Thanks for the tip. I'm running a 1600 pinto. What is your temp switch set at, and what engine do you have?

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There's more than one way to skin a cat, but the top hose method works for me. I have a 2.0L Pinto with an old school Kenlowe capillary controller (don't know if you can still get them?), the setting is half way between the "N" and the "H"; what that equates to numerically I don't know, but I know the fan comes on in traffic on a hot day 😆. It has never overheated so far 🤞. The dial allows you to set the operating temp yourself. It's also a high current switch so (for mine) no fan relay was needed (unless your fan draws more current than the switch rating).

Edited by RedTrev
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