Technical One Radiator and Two Fans

[stevenk9958]

I have a 1978 Fiat 124 Spider 1800 and am getting ready to install the radiator. Much to my surprise, the buyer included a large yellow radiator cooling fan whose housing matches the bolt brackets and holes on the radiator which I haven't installed yet (see picture 1). When I turn the radiator over there is a smaller fan already installed on the radiator (see picture 2). Why two fans? Do I ignore the bigger yellow bladed fan and not install it and just use the smaller fan already installed? Do I use both? Thanks for any guidance you can provide.

 

[Slotman]

The yellow one is the original fan to the car...the other one is a small aftermarket fan, not sure why someone took off the original one unless it stopped working...

 

[stevenk9958]

Thanks Slotman. I tested both motors today and they both work. The smaller black fan is mounted on the back side of the radiator so it will take cooler air from the outside and blow it through the radiator into the engine bay. The yellow fan would do the opposite blowing engine bay air through the radiator to the front of the car. Do you think it makes a difference which one I use? The smaller black fan is already mounted onto the radiator, should I just leave it and use that one or remove it and use the yellow fan since it is factory? Thanks for your opinion.

 

[Slotman]

I'm thinking you have the concept wrong...the factory yellow bladed fan actually pulls air in from the front of the car, from the backside of the radiator,(engine side" ) thru the radiator, and blows it back across the motor towards the firewall..the same way as if your driving and the wind is blowing from the front bumper in the direction of the motor, perhaps if you were bench testing it you mixed up the leads and it was running backwards? The yellow bladed fan should not be blowing in the direction thru the radiator towards the front bumper...if it was me I would run the stock yellow fan and verify its blowing "back" across the motor, and perhaps put the aftermarket fan in the "front" of the radiator just behind the grill so it's "pushing" air as the factory fan is "pulling" air ...then you have double the cooling...my factory fan turns on at exactly 190 degrees from the factory thermostat,...your aftermarket fan may have been wired with just a switch to turn it on anytime rather that thru a thermostat unless you saw

one..P.S. if you decide to run both fans as i mentioned you have the option of wiring it to the factory thermostat so it turns on at the same time as the factory fan but personally I would wire it to just a switch so you can run it after the key and ignition is off if the car is hot..

 

[timmycm850]

I would run the std fan via the fan switch so it comes on automatically when needed. Also wire up the aftermarket one on a separate manual switch as slot man says so you can have the fan running after you park up. Also if you find yourself in traffic you can manually turn it on to keep it at regular temperature before it gets hot. This will also help reduce fuel vaporisation in real hot weather.

 

[Twink80]

I have a 1978 Fiat 124 Spider 1800 and am getting ready to install the radiator. Much to my surprise, the buyer included a large yellow radiator cooling fan whose housing matches the bolt brackets and holes on the radiator which I haven't installed yet (see picture 1). When I turn the radiator over there is a smaller fan already installed on the radiator (see picture 2). Why two fans? Do I ignore the bigger yellow bladed fan and not install it and just use the smaller fan already installed? Do I use both? Thanks for any guidance you can provide.

One fan should be enough to cool a stock motor, maybe more marginal if you contibually drive hard in 40-50degC ambient temps
I would remove the small black fan or mount it on an isolated bracket. The radiator core tubes are very thin and vibration of normal running can cause the plastic fan to wear thro the tubes and the rad will leak
My final point is you need to get the air out of the engine bay as well as trying to push it in. These type of fans are not fixed displacement and have a limit to the pressure rise (amount of air) across the fan. There are a number of seals around the edge of the bonnet, the engine bay is spacious (unlike modern european cars) so the airflow will be predominantly around the engine and down the transmission tunnel when driving. The fan is to provide an airflow boost in slow traffic or stationery.

 

[stevenk9958]

Thanks for your comments Twink80. I decided to remove the smaller black fan and just go with the manufacturer's yellow one. Frees up the entire radiator surface for cooling plus I don't want to fool around with an on/off switch for that 2nd fan.

 

[stevenk9958]

I would run the std fan via the fan switch so it comes on automatically when needed. Also wire up the aftermarket one on a separate manual switch as slot man says so you can have the fan running after you park up. Also if you find yourself in traffic you can manually turn it on to keep it at regular temperature before it gets hot. This will also help reduce fuel vaporisation in real hot weather.

Thank you for your suggestions.