[Glavas]

Installing a thermo fan soon (picking it up today)

Going to just have it operated by a switch in the cabin. However I'm not sure on;

gauge of wiring necessary
what kind of relay I need
what kind of fuse I need

The switch I'm using is a 20A switch with an LED in it so I can tell if i've forgotten to turn it on.

Any input on what the fuse/replay/wiring?

[ck13488]

generally the thicker the wire the better. you need to find out how many amps the fan draws then look for a table like this to determine the guage needed.

just a normal 'open' relay will do (30/85/86/87 pins) and rated above the current you have determined you need

[Glavas]

ck13488 wrote:

generally the thicker the wire the better. you need to find out how many amps the fan draws then look for a table like this to determine the guage needed.

just a normal 'open' relay will do (30/85/86/87 pins) and rated above the current you have determined you need

That's what I was hoping for, basically just go as big as possible?

How about the fuse though?

[ck13488]

i would go as big as possible but maybe a few guages bigger if you have the wire already.

not 100% on the fuse...but i think its +20% on the current being drawn?

[Glavas]

Might just stick a 30 in and see how I go.

[lump_a_charcoal]

Tell us the current of the fan, we will tell you the minimum size cable required.

[ck13488]

do you know how many Amps or Watts the fan needs?

just sticking a fuse in can = burnt bits!

[Glavas]

No idea, getting it second hand from a mate. Hopefully it's on the fan somewhere.

I suppose I could test it.

Thanksfor your help too.

[lump_a_charcoal]

It should be printed on the fan somewhere, otherwise grab a tong meter, hook it up to your battery and find out the current drawn.

Or get the resistance of the windings.

[Glavas]

Resistance of the windings will be easiest

[foonji]

From memory my 14" Davies Craig thermo fan draws 11amp and the fuse is 15amp and it sounds like a Super Hornet about to take off

[Glavas]

this is only a 12.5" fan so probs change that to a 15amp ruse

More worried about the alternator's ability to keep charge on this especially with the other things I have coming for the sierra.

Might need to upgrade the alternator...

[atari4x4]

I think you might find unless the thermo fan is properly shrouded you might not get enough cooling from it.... unless are you going to run it with the original engine fan?

[Glavas]

atari4x4 wrote:

I think you might find unless the thermo fan is properly shrouded you might not get enough cooling from it.... unless are you going to run it with the original engine fan?

Don't understand that? run it with the original fan? :O

I'll see how it goes without a shroud. If it has problems, I'll make up a shroud.

My car seems to have some very slight, very intermittent overheating problem. Cruising at high revs temp gets up a bit. Thermostat is fine, Coolant level and condition is okay.

Gonna try a thermo fan to fix it

[matty_wall]

Glavas wrote:

atari4x4 wrote:

I think you might find unless the thermo fan is properly shrouded you might not get enough cooling from it.... unless are you going to run it with the original engine fan?

Don't understand that? run it with the original fan? :O

I'll see how it goes without a shroud. If it has problems, I'll make up a shroud.

My car seems to have some very slight, very intermittent overheating problem. Cruising at high revs temp gets up a bit. Thermostat is fine, Coolant level and condition is okay.

Gonna try a thermo fan to fix it

I run the normal clutch fan and a thermo on the front.

[Gwagensteve]

If you plan on removing the factory fan, there is NO WAY a 12.5" fan will keep the car cool. Just 100% no way. Even with a great shroud.

Firstly, how is your car set up? Is it a mostly stock sierra? If so, it shouldn't overheat on the highway. You need to try and find out why it's overheating before you remove a functional stock fan and replacing it with a fan which will create more problems.

Next, if you do want to run a thermo, I don't think you've taken everything into account.

How are you controlling the fan? Are you just running it on all the time? That's a silly idea. Thermos consume lots of amps - you want it off when it's not required. There are stand alone fan controllers available, or you could build a Jaycar kit - that's what I did:

http://www.jaycar.com.au/productView.as ... eyword2=KC


The whole advantage of a thermo is that it's only on when required, so the total power consumption is reduced.

There's no such thing as a free lunch.

Let's say your current engine driven fan consumes 1Kw @ 3000rpm. (It might be a bit more than that, but let's stick to that for now)

For an electric fan to move as much air under same circumstances, it must also consume roughly 1Kw. That's 1000W, or roughly 83 amps at 12V.

Thermo's don't use anywhere near that much power - and that's a clue - they don't draw anywhere near as much air as the engine fan either- but they still consume quite a lot of power - as I said, over 20A, or 240W, or .24Kw... but your alternator isn't very efficient..... so if you are running the fan all the time, you might be pulling almost the same power out of the motor than the bigger, more reliable, and more effective mechanical fan was drawing in the first place.

It also explains why lots of cars with thermo's don't cool as well as with the stock fan. (That's been my experience with a number of sierras too)

Your stock alternator produces 50amps maximum.

When your car is idling, the engine fan might only consume 200W or so.... but your thermo is still running flat out and drawing 1KW of power out of the engine. It's not smart.

Yes, you will need a relay.

You need to control the fans operation.

If you want a manual override, IMHO wire the circuit so a buzzer sounds if the switch is in the 'off' position. I've seen too many cars overheated because the driver forgot to turn the fan back on.

You need to look into a very high quality fan. Search for SPAL, and look at going up to 14"

You'll need to investigate an alternator upgrade.

Or, if you have a sierra, just look into fitting a vitara viscous fan. They are much larger and have cured a number of sierras with overheating problems. The shroud will need modification but the fan is a bolt in and much, much larger.



On the left, a stock 1.0 litre 4 blade fan. In the centre, a Vitara fan, on the right, a 1.3 sierra fan.

I would run one of these before a thermo in a sierra in an instant.

My own car runs thermos, but they my cooling system is a little different to most. They work very well for me, but they are well shrouded, well switched, and the radiator is massively oversized for the application. They are also factory thermos - (Camry) - much better quality than most aftermarket thermos.

[whincup]

Gwagensteve wrote:

Let's say your current engine driven fan consumes 1Kw @ 3000rpm. (It might be a bit more than that, but let's stick to that for now)

For an electric fan to move as much air under same circumstances, it must also consume roughly 1Kw. That's 1000W, or roughly 83 amps at 12V.

Thermo's don't use anywhere near that much power - and that's a clue

this doesnt sound right to me... you need to remember that the fan isnt DIRECTLY cooling the engine, its pushing air over the radiator and the air is cooling.

for example, if you flattened the blades rather than them being on an angle, they would take more force to turn, but actually cool less since theyre not sucking air through...

i have no experience with thermos so im not going to comment on better/worse and how big needed, etc, just pointing out that the maths here is irrelevant... no offence

[lump_a_charcoal]

He isn't talking about cooling efficiency, he is talking about power consumption of the two methods.

[Fatzook]

I run a 14" SPAL fan on my sierra with custom shroud and it works floorlessly.

I also run an overide switch, but the fan is controlled by a digital unit that is adjustable from in the cab. (unfortunately it is in Farenhiet, so you need to learn that temp scale)

Works great!

[Gwagensteve]

Lump is correct I wan't talking about cooling efficiency - I was talking about power consumption. The power can only come from one place- The engine. Converting rotational power into volts then back into rotational power 4" from where it was in the first place is silly, especially when there major limitations in the system (like alternator power)

Yes, an electric fan might have efficiency improvements over a mechanical fan, but physics are still physics, the energy required to turn a fan is a factor of the amount of air it's moving. More air moved = more power consumed= more potential for cooling.

Many thermos don't move enough air to cool an engine as the primary fan. Assuming fitting a thermo (whilst removing the engine fan) will improve cooling is false.
Assuming fitting a thermo will improve engine performance might also be false - due to inefficiencies of converting crank RPM into electricity, the smaller amount of watts required to drive the thermo might place just as much load on the crank (via the alternator) as the stock mechanical fan.

The gain is that a thermo doesn't have to run all the time like a sierra mechanical fan. However, neither does a viscous fan as used in a Vitara. compare a large viscous fan to a thermo and the advantages of the thermo aren't as obvious.

Fatzook - I have no doubt you have no trouble with a digital controller and a 14" Spal fan.

That's a long way from a switch and a 12.5" unknown thermo though.

Steve.

[Fatzook]

Gwagensteve wrote:

Fatzook - I have no doubt you have no trouble with a digital controller and a 14" Spal fan.

That's a long way from a switch and a 12.5" unknown thermo though.

Steve.

Yeah sorry

[whincup]

Gwagensteve wrote:

Lump is correct I wan't talking about cooling efficiency - I was talking about power consumption.

ok well i missed that... but one question... with stock fan, engine is spinning fan and alternator to produce power... thermo fan, engine is only producing power. isnt the alternator already producing electricity regardless of whether its spinning a fan, wouldnt be better to harness that rather than waste it?

[Fatzook]

I'm sure that people over think this issue.

A properly setup thermo that turns itself on and off doesn't actually use that much power. Assuming your radiator is in good condition, then half the time your thermo is off, there is no load on the engine from a fan, and the alternator is generating power as it usually does. Then the thermo kicks in, there is a small spike in current draw, then levels out and may draw 25A for about a minute ( if its not a completely shit fan, this should be enough time to cool the engine about 7-10degrees). Then it goes back to no load on the engine and alternator doing its thing.

A viscous fan works in a similar way.

An engine fan loads the crank all the time.

IMO its 6 of one, half a dozen of another

[whincup]

Fatzook wrote:

IMO its 6 of one, half a dozen of another

this has to sum it all up best

[SuziBlu]

Stock fans have nowhere near the efficiency of the blades as your better quality thermos, and that makes for very large air movement at reduced power consumption.

I love thermos, anytime I get a vehicle with an engine driven fan, 1st mod, before all others, is a thermo.

[Fatzook]

SuziBlu wrote:

Stock fans have nowhere near the efficiency of the blades as your better quality thermos, and that makes for very large air movement at reduced power consumption.

I love thermos, anytime I get a vehicle with an engine driven fan, 1st mod, before all others, is a thermo.

1st mod for me is to fit an EFI motor
Then thermo

[SuziBlu]

I couldnt find EFI, so I bought Throttle body off smileysmoke, but he kept both the throttle body and my money, so im stuck with carby, when Im dun building my toy, itll probbably get a coil pack baleeno donk.

[Fatzook]

SuziBlu wrote:

I couldnt find EFI, so I bought Throttle body off smileysmoke, but he kept both the throttle body and my money, so im stuck with carby, when Im dun building my toy, itll probbably get a coil pack baleeno donk.

HAHAHA Sorry that shit aint funny Its just the way you said it

Yeah Baleno is where its at

[SuziBlu]

ya goda larf, or ya cry hey. Was meant to be light.

[DMAC]

Fatzook wrote:

I'm sure that people over think this issue.

A properly setup thermo that turns itself on and off doesn't actually use that much power. Assuming your radiator is in good condition, then half the time your thermo is off, there is no load on the engine from a fan, and the alternator is generating power as it usually does. Then the thermo kicks in, there is a small spike in current draw, then levels out and may draw 25A for about a minute ( if its not a completely shit fan, this should be enough time to cool the engine about 7-10degrees). Then it goes back to no load on the engine and alternator doing its thing.

A viscous fan works in a similar way.

An engine fan loads the crank all the time.

IMO its 6 of one, half a dozen of another

What is the normal operating temperature range for a Sierra?

Or what temps have you set the thermo to cut in and cut out?