Computer Fans to cool Alternator??

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Trident

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So I bought a job lot of computer fans to cool fridge compressors etc and have a couple left over. My Hitachi alternator on the Yanmar 3GM gets very hot and I wondered if these might help? My guess is they're just too small to make a significant difference in the engine bay even if very close to the alternator but has anyone tried this and had any success?
 
Trident said:
So I bought a job lot of computer fans to cool fridge compressors etc and have a couple left over. My Hitachi alternator on the Yanmar 3GM gets very hot and I wondered if these might help? My guess is they're just too small to make a significant difference in the engine bay even if very close to the alternator but has anyone tried this and had any success?
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I think you're right. If you can seal your engine compartment fairly well and then duct outside air in through a 4" hose (Eberspacher type) with its end close to the alternator, the incoming air will help to cool the alternator automatically.
 
pvb said:
I think you're right. If you can seal your engine compartment fairly well and then duct outside air in through a 4" hose (Eberspacher type) with its end close to the alternator, the incoming air will help to cool the alternator automatically.
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+1 if you are able to do this.

Don't forget that the fan on the front pulley of the alternator sucks air right through the body of the alternator from the end with the connections through to the pulley end so your cool air ducting needs to be fixed close to the connections end.

Richard
 
oio
RichardS said:
+1 if you are able to do this.

Don't forget that the fan on the front pulley of the alternator sucks air right through the body of the alternator from the end with the connections through to the pulley end so your cool air ducting needs to be fixed close to the connections end.

Richard
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Both my Benes have/had 3" fans in the engine bay with 3 by 4" ventilation hoses coming from the sugar scoop, with one exhausting the fan hot air.
Both were not working when I aquired the boats. I soon sorted that! The point I am making is that they work continuously and pull hot air from the engine compartment. I have fitted a Sterling alternator booster and when it is chucking out 50 amps it gets seriously hot! However it has continued to be ok. Without the exhaust fan I suspect that it might be a prob!
S
 
Agree, I have a single computer fan in my engine bay door linked to a household thermostat unit, it pulls a significant amount of heat from the engine bay, I think it is worth considering.
 
I think that's a 1000cc engine. At 2000 rpm that's taking in 2m3 per minute of airflow so a passive air vent near the alternator should be a lot more effective than a computer fan.
 
As has been said, putting a passive intake vent that flows over the alternator will put many, many times more air across the alternator. Plus it will be nice chilly outside air. An alternative would be a bilge blower, about 1amp and wired into the ignition.
 
Colvic Watson said:
As has been said, putting a passive intake vent that flows over the alternator will put many, many times more air across the alternator. Plus it will be nice chilly outside air. An alternative would be a bilge blower, about 1amp and wired into the ignition.
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There is two issues here. Engine room airflow across the alternator and cool cabin/bilge air flow ducted to the alternator. At engine room temperatures you need a very high flow rate to cool the alternator. An alternator temperature of say 65degC with engine room at 40 degC only has 25 degC temperature difference to cool the alternator. If you can introduce cool cabin air at 20degC to the alternator, you will substantially increase the temperature difference and therefore the cooling effect. Using an inline bilge blower with some flexible ducting to the front of the alternator to pull cool bilge air to the alternator will have a substantial cooling effect.
Reducing the engine room air temperature by installing a high level extract fan discharging straight to outside will help. In my experience in the tropics my engine room can be held down to 40 degC with the use of a powerful centrifugal fan ducted to atmosphere. When the fan failed the engine room temperature climbed up to 55 degC.
 
You should try server fans....search ebay for dl380 fan....cheap and they shift loads more air....not very quiet mind you...but that won't matter.
 
Are you sure the alternator is turning the correct way?
They will generate either way, but need to have the "air moving device" on the front matched to rotational direction in order to suck air through from the rear , I drilled extra holes in the back of my bosch (from a car scrappy) in order to help the airflow.
 
Billjratt said:
Are you sure the alternator is turning the correct way?
They will generate either way, but need to have the "air moving device" on the front matched to rotational direction in order to suck air through from the rear , I drilled extra holes in the back of my bosch (from a car scrappy) in order to help the airflow.
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Good point.
Some have an internal fan.

Things like alternators may be designed to run fairly hot by domestc standards.
 
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