Thermo Fan

[slyr32]

I am putting a thermo fan in my 31 with a RB20! what temperature do i need the fan to turn on at? thannks

[Deano 1]

thermostat's norm open between 60-70deg so set it somewhere around there?? so the thermos turn on when the thermostat opens

[mad082]

generally the thermostat will open about 85 degrees. if you are running aircon you will want it on most of the time when the aircon is on. if not running aircon then you could still have it come on around 70 degrees. that said, in the missus SSS pulsar, with the aircon off it doesn't turn on until 100 degrees if doing below 20kms, and over 20kmh it turns on at 95 degrees (taken from the workshop manual).

[blind_elk]

Thermo fans do not need to turn on until quite high temps, certainly more than 10 degrees above the thermostatted temperature.

The fans are employed because the bulk of the cooling is covered by the fact that the car is moving and air is going through the radiator, thus cooling the engine. So why does the engine need to drive a fan if the air movement is doing the job? Having the thermo fan operating all the time or when the thermostat is open is a waste of resources, and simply shifts the load on the engine from driving a fan to driving the alternator.

[lachlanw]

surely the fan needs to come on below thermo stat temperature . how the f**k is putting water the same temperature back into the engine going to cool the engine?

put a tridon tfs141 thermo switch in the bottom radiator tank . problem solved

youll probably find itll bolt into the factory hole .....

[chuckie]

Well we all have different thinking,

I used Tridon TFS 153 in middle of mine,

i have 1980 VC wagon set up with thermo`s MONDAO twin`s water pump high flow bypass kit & fail safe just incase Switch fail`s & fan`s will come on if that dose happen ,as it did when i first had them set up,& has been sweet as since then,

Now i will look at Same set up on MY STAGEA in time,with Factory FAN`S from Nissan Maxima,

Many say THERMO`S are usless & some think there ok ,

But Think about if your SWITCH FAIL`S WHAT WILL COOL WATER THEN,

Cheer`s Chuckie.

[ARTZ]

surely the fan needs to come on below thermo stat temperature . how the f**k is putting water the same temperature back into the engine going to cool the engine?

put a tridon tfs141 thermo switch in the bottom radiator tank . problem solved

youll probably find itll bolt into the factory hole .....

if the thermastat is closed no water is flowing through the engine...isnt that what a thermstat does?..stops water flow until engne is at operating temperature...So once the water is flowing is about when the fan should come on...cause until then it is still water so having the fan on is useless..

Edited June 21, 2010 by Arthur T3

[blind_elk]

surely the fan needs to come on below thermo stat temperature . how the f**k is putting water the same temperature back into the engine going to cool the engine?

put a tridon tfs141 thermo switch in the bottom radiator tank . problem solved

youll probably find itll bolt into the factory hole .....

That's just my point. The water is not "the same temperature", it is cooler because it has passed through the radiator and has exchanged heat with the cold air that is passing through the radiator by virtue of the fact that the car is moving.

Having the fan thermostat set higher - as high as 100 - is only a problem when the car is stationary, like in peak hour stop-start traffic. But that is generally only for short periods of time - as soon as the car gets up some speed again, the water will cool down to near the thermostatted temperature, even if the thermo fan has not cut in.

If you don't believe me, why not try it.

[pipster11]

if the thermastat is closed no water is flowing through the engine...isnt that what a thermstat does?..stops water flow until engne is at operating temperature...So once the water is flowing is about when the fan should come on...cause until then it is still water so having the fan on is useless..

what? i may have read you wrong but when the thermostat is closed water still flows around the engine, just not into the radiator (hence when having no thrmostat is bad for your car)

as to the op

you still get heat transfer with water going through the radiator, but airflow through the core increases the amount of energy from the water goes into the surrounding air

and yes, you want the fans to come on AFTER the thermostat opens otherwise the temp will stay below the thermostat temp and it'll take ages to come up to temp = chewing more fuel and running on cold maps longer

colder engines make less power and use more fuel, you want a coolant temp of around 85 consistantly (in traffic or giving it a lash)

[lachlanw]

its doesnt matter what the f**k your thermo stat is doing .

the job of the fan is to move air through the radiator when there is not enough air moving through it .

if the water in the bottom of the radiator is approaching engine operating temperature the the radiator is not doing its job properly , oh what to do ? turn on the f**kin fan .

and yes put a overide switch in it . or even better hook it to the factory fan wire that comes on when the ac is on or the engine is too hot

the ultimate is 2 speed fans . one speed wired to thermo switch in bottom of radiator other speed wired to factory fan switch so comes on with ac and engine over heat . so either causes half fan and worse case scenario is full noise

and put an overide switch

[lachlanw]

and obvoiusly no fan is going to be on before the engine is up to temperature . making that piont null and void

[blind_elk]

and obvoiusly no fan is going to be on before the engine is up to temperature . making that piont null and void

But you said in post#5 that

surely the fan needs to come on below thermo stat temperature

So what is it - on or off below thermostat temp?

Clearly you have no understanding whatsoever about the principle behind the thermo fan and its use in automotive applications.

Humour me and run your car for 1 day with the power to your thermo fan disconnected - let us know if you have major dramas with overheating.

[lachlanw]

But you said in post#5 that So what is it - on or off below thermostat temp?

Clearly you have no understanding whatsoever about the principle behind the thermo fan and its use in automotive applications.

Humour me and run your car for 1 day with the power to your thermo fan disconnected - let us know if you have major dramas with overheating.

the fan needs to come on before the water temperature in the RADIATOR is near the temperature that the thermo stat is set at

the engine and the radiator are two seperate systems the engine only over heats when the radiator is not doing its job.

clearly you do not under stand

the fans job is to move air through the radiator when there is not enough air flowing through it naturally

or does it have another job in your all knowing world??

how do you know if the radiator is not getting anough air ? it heat soaks and the bottom tank approaches the same temerature as the top tank ( which is full of water that just passed through an 82 degree thermostat)

humour me and disconnect your key board while your brain is trying to work

[lachlanw]

all this time i have been talking about the temperature in the bottom tank of the radiator

which is important in fan function

you have been talking about engine temperature . which is really a delayed (and possible expensive ) way to tell you the radiator is not getting enough airflow and not cooling the water enough so your engine over heats

agree to disagree?

[blind_elk]

Don't beleive me then, maybe you will believe the manufacturer.

From the Davies Craig instruction sheet - Setting the Thermal Switch:

Turn thermal switch adjustment fully clockwise. The fan(s) should turn off.

Run engine until the engine temperature is about halfway between "normal highway operating temperature" and "too hot". This will indicate a coolant temperature between 5 and 10C higher than normal.

Immediately, turn adjustment very slowly anti-clockwise, just until fan(s) switches on and no more.

Allow the fan to run long enough to reduce the temperature by about the thickness of the temperature gauge needle before it turns itself off.

On a cool day, it should run between 30 and 60 seconds. On a hot day it may be somewhat longer.

If the fans run for more than a few minutes at a time, turn the adjustnment clockwise slightly to increase the cut-in temperature. The fans must be set to cut in above normal operating temperature, otherwise they will run more frequently and for longer periods than necessary, and you may not achieve all the benefits of electric cooling.

[ARTZ]

what? i may have read you wrong but when the thermostat is closed water still flows around the engine, just not into the radiator (hence when having no thrmostat is bad for your car)

You read right but I did word that wrongly...i meant through the radiator ,there is no point having a fan going when the water isnt flowing

Blind elk is all over this one.. When thermostat opens the water in radiator will be cooler than that in the engine so will actually cool the engine for a short time, as it warms up and starts to get over op temp then the fan should come on to cool it Once its back to temp it should stop agian and so on and so on ...

[warps]

Lachlan vs the world raises a valid point. The coolant temp is generally read at the thermostat, so if the temp probe for the switch is near the thermostat, then you need to set the temp slightly higher than the thermostat opening temp.

If you've set the temp probe in the bottom tank, then this is supposedly cooler than the top tank, so you will need to set the switch lower.

If the radiator outlet water temp is the same as the inlet temp, then correct, there is no heat being removed from the water.

100 deg C water will still cool engine components (some of which are approaching several hundred degrees C) but obviously we start having issues with the water boiling, not being pumped around, effective cooling etc. However, setting the fan to cut in when the radiator outlet temp is higher than the thermostat temp may in fact cause problems as Lachlan has said (because it is coming back into the engine much hotter again). I don't know what the limits are, as I haven't been dumb enough to try this.

[mad082]

You read right but I did word that wrongly...i meant through the radiator ,there is no point having a fan going when the water isnt flowing

Blind elk is all over this one.. When thermostat opens the water in radiator will be cooler than that in the engine so will actually cool the engine for a short time, as it warms up and starts to get over op temp then the fan should come on to cool it Once its back to temp it should stop agian and so on and so on ...

but as it says in the quote he posted, it says nothing about the fan turning off due to the coolant being tool cold, just that you won't be getting the full effect of electric cooling (less drain on the engine) and puts extra stress on the fans.

this is where i refer back to the stock settings on the fans on a car that came out with thermos from factory. on the pulsar nissan has it that the fans come on when the aircon is on regardless of engine temp. this means that even if the car is stone cold the fans come on. pretty much any car with factory fitted thermos will be the same. this means that it can't be that bad to have the themo on before the car is at operating temp, and i've never found to it affect how long the car comes up to temp. the car still comes up to temp faster on a hot day with the aircon on from the moment i start the car than it does on a cold day with the aircon off. but as i said earlier, if the aircon is off the fans don't kick in until much higher.

here's a pic of the setup from the workshop manual