givemethebighammer
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| posted on 10/5/04 at 09:43 PM |
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Nissan Micra Rad Fan
Been messing about with my Nissan Micra radiator fan this evening just need to ask a few questions:
the fan unit has three wires going into it
1. Black
2. Blue and red
3. Yellow
I have established that the black and yellow wires connect via the thermostatic switch in the radiator, hence "rad hot" fan operates.
However when connecting the blue \ red and black wires the fan operates when the radiator is cold. Is the Blue \ red wire for a manual switch or did
it do something else on the original car. The fan spins at the same speed regardless of whether you connect yellow and black or blue\red and black
wires.
Also I take it that the fan should be drawing air through the radiator (i.e. from front to back) and not blowing air (back to front) as it is a rear
mounted fan.
thanks
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Hellfire
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| posted on 10/5/04 at 11:23 PM |
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I had this similar dilemma.
The Red/Blue we have as permanent fused positive which feeds the Thermo.
At this late hour - I believe the yellow is negative (earthed) when thermo is in switched position so powering the fan.
Black is a return to the temp. gauge in the car. (We didn't use as we had the bike thermostat and clocks)
Our fan is behind the rad and pulls air through the rad.
I'll check for you - will post tomorrow night!
[Edited on 10-5-04 by Hellfire]
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spunky
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| posted on 11/5/04 at 12:05 AM |
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GMTBH, when I was connecting the fans in mine I was baffled by the circuit and came to the conclusion that it was to allow the fan to run on after the
ignition was switched off. I used the wires to connect a thermostat overide switch on the dash.
Mid engined and rear radiator, reckon it will get some use....
PS. Can anyone tell me, why do car and bike fans run on after shutting down the engine? I see no advantage in cooling a bit of water in the rad.
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givemethebighammer
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| posted on 11/5/04 at 08:41 PM |
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I had almost come to the conclusion to use the yellow and black wires and ignore the blue / red one. Zetec engine (known to have overcooling issues),
small front radiator... shouldn't need a manual fan switch..........hopefully
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Hellfire
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| posted on 11/5/04 at 11:03 PM |
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GMTBH - busy doing "other stuff" tonight. Sorry for the delay - will post later in the week - away on business from tomorrow (erm,
today!).
Hope you're not in a hurry!
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splitrivet
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| posted on 12/5/04 at 04:16 PM |
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quote:
Originally posted by spunky
PS. Can anyone tell me, why do car and bike fans run on after shutting down the engine? I see no advantage in cooling a bit of water in the rad.
Its to dissipate any latent heat from the system,when you turn the engine off the blocks still hot and could still rise above a safe
temperature/pressure older mechanically cooled rads were oversized to allow for this, modern rads are much smaller so thats why they continue to be
cooled.
Cheers,
Bob
I used to be a Werewolf but I'm alright nowwoooooooooooooo
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spunky
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| posted on 12/5/04 at 05:15 PM |
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quote:
Originally posted by splitrivet
Its to dissipate any latent heat from the system,when you turn the engine off the blocks still hot and could still rise above a safe
temperature/pressure older mechanically cooled rads were oversized to allow for this, modern rads are much smaller so thats why they continue to be
cooled.
Cheers,
Bob
Thanks Bob,
Obvious now I think about it..
Cheers
John
[Edited on 12/5/04 by spunky]
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Hellfire
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| posted on 12/5/04 at 08:24 PM |
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I agree with the theory of heat dissipation re the radiator fan over-run. However I am unaware of an engine management system that circulates the
coolant after engine shutdown, therefore is it not only the coolant in the radiator which cools?
The way the system on our BEC is, the fan cooled water from the radiator simply rests at the bottom of the radiator as everything else is physically
higher and this is where the hottest water will accumulate.
Or am I in the wrong tree 
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Peteff
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| posted on 12/5/04 at 08:55 PM |
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The water will circulate by convection till the stat shuts. As the hot water at the top cools it drops and is replaced by hot water from the engine
via the top hose.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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