pajsh
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| posted on 23/7/06 at 03:33 PM |
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Electric Radiator Fan
My electric radiator fan is wired direct to the battery and so runs on when the engine is switched off.
It occurred to me it may not actually be doing anything once the engine is turned off and the water pump is no longer working.
Is it worth having it running or not. It runs for quite some time before the thermo switch cuts it off.
I used to be apathetic but now I just don't care.
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stevec
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| posted on 23/7/06 at 03:42 PM |
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I would say that when you switch off there is quite a bit of heat that builds up and some of this will travel to the rad. So it cant harm to get rid
of a bit of it.
Steve.
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RichieC
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| posted on 23/7/06 at 03:49 PM |
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In an ideal world youd have an electric water pump connected with the fan so that it runs when the fan does.
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Hellfire
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| posted on 23/7/06 at 04:11 PM |
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We had that very same idea not very long ago... best bet is to prevent overheating rather than cure it.
Therefore, wire in a manual switch and leave the engine running for a minute or so with the fan on just in case... this is what we have done!
It's designed to do that on the ZX12R as new... they already have a manual aswell as auto trip on the fan. Marvellous those Japs!!!
Steve
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RazMan
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| posted on 23/7/06 at 05:37 PM |
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quote:
Originally posted by RichieC
In an ideal world youd have an electric water pump connected with the fan so that it runs when the fan does.
That works a treat & it is good to know that all the heat from that blast round the lanes will not soak in and boil the coolant while you are in
the pub 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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zetec7
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| posted on 23/7/06 at 06:18 PM |
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Provided it doesn't wear down your battery, there's nothing wrong with that setup. Lots of cars have that built-in...my Porsche 944 does
that (although there is a relay that reduces the fan to 1/2 speed when the engine's off), and sometimes runs for 5-6 minutes. It takes heat
away from the entire engine area as well as the radiator...
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matt_claydon
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| posted on 24/7/06 at 08:34 AM |
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Apparently convection currents will keep the coolant flowing (slowly!) round the circuit even without the pump. Don't know about the truth of
that but I read it somewhere.
AFAIK most modern production cars have the fan wired so it'll run with the engine off. No need to worry about the battery unless it's
really really really small, the fan won't ever run for more than a few minutes.
[Edited on 24/7/06 by matt_claydon]
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02GF74
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| posted on 24/7/06 at 01:15 PM |
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quote:
Originally posted by matt_claydon
Apparently convection currents will keep the coolant flowing (slowly!) round the circuit even without the pump. Don't know about the truth of
that but I read it somewhere.
[Edited on 24/7/06 by matt_claydon]
that is true. in the very early days, there was no water pump and the water circulated by siphoning action - that is why your radaitor is wired so
hot water goes in at the top and as it cools, it becomes denser and sinks to the bottom causing a flow - it stops when the thermostatat closes.
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John Bonnett
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| posted on 24/7/06 at 03:34 PM |
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The process is call thermo-syphon. Even reasonably modern cars, ahhh I'm talking 60 years ago sign of age, had no water pumps but water
circulated because the hot water from the engine rose to the top of the radiator pushing cold water out at the bottom and into the block. Cars in
those days had no heaters but Ford did market an "Export" water pump with heater take offs. This was an external fitting and did not
circulate coolant.
Anyway, back to the question. Yes it is normal for the fan to be independent of the ignition switch because the engine will heat up just after it has
been switched off and it is quite usual and desirable for the fan to take away this heat by running until the temperature drops.
John
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