Rad Fans?

DaveEFI · Post by **DaveEFI** » Wed Jul 24, 2013 11:11 am

Assuming your MS is reading the actual temp - ie no air pockets etc - I'd measure the rad where the fan switch is using an infra red thermometer.

Water is funny stuff - you can have a big temperature differential within a very close distance, if the water is still. Think of a domestic hot water cylinder - can be piping hot at the top, stone cold at the bottom. Now pumping the water round should equalize this - but there could still be pockets of air, or parts of the coolant that don't move much. And if the sensor sits in one of these, it won't give an average reading.

Post by **Coops** » Wed Jul 24, 2013 8:20 pm

like I said its been faultless until the cooler was fitted,

Any one using MS2 V3 to run a cooling fan via the fiddlewire?

DEVONMAN · Post by **DEVONMAN** » Wed Jul 24, 2013 10:32 pm

Some questions to help clarify things.

-Do the fans switch off at some point as the engine cools?
-Is it a 2 pin fan switch?
-Does the fan switch provide an earth to the relays or 12v?
-What is the Contact rating of the fan relays? (Cossie fans eat light weight relays)
- Are the fan switches you are using normally used in a plastic rad tank and not an aluminium tank.
-What position is the fan switch in the rad?
- If you disconnect the fan switch do the fans stop?

DaveEFI · Post by **DaveEFI** » Wed Jul 24, 2013 10:57 pm

Coops wrote:like I said its been faultless until the cooler was fitted,

Any one using MS2 V3 to run a cooling fan via the fiddlewire?

Think any of the spare ports can be used, although you may have to add a transistor driver for the relay. Although I'm not well up in the v3.57 board - prefer the V3 myself.

The obvious one to use, if not already in use, would be the Fidle, since that has an output stage to drive a relay.

Post by **Coops** » Thu Jul 25, 2013 7:26 am

"DEVONMAN"]Some questions to help clarify things.

-Do the fans switch off at some point as the engine cools? YES
-Is it a 2 pin fan switch? YES
-Does the fan switch provide an earth to the relays or 12v? EARTH
-What is the Contact rating of the fan relays? (Cossie fans eat light weight relays) 40AMPS EACH
- Are the fan switches you are using normally used in a plastic rad tank and not an aluminium tank. PLASTIC AS PER FACTORY
-What position is the fan switch in the rad? FACTORY POSITION NEAR THE BOTTOM NEAR THE BOTTOM HOSE
- If you disconnect the fan switch do the fans stop? YES

DaveEFI · Post by **DaveEFI** » Thu Jul 25, 2013 8:32 am

Coops wrote:"DEVONMAN"]Some questions to help clarify things.

-What position is the fan switch in the rad? FACTORY POSITION NEAR THE BOTTOM NEAR THE BOTTOM HOSE

Interesting. The factory one on my SD1 is just down from the top (crossflow rad) On the other side from both the hoses.

Post by **Coops** » Thu Jul 25, 2013 8:40 am

This is a factory Audi rad that I have used for years

stevieturbo · Post by **stevieturbo** » Thu Jul 25, 2013 9:49 am

Is the rad the correct way up ?

Normally a fan switch would be towards the top of the radiator ? Or in the top hose itself ?

May not always be the case though

Either way, I'd still be using the ecu

Post by **Coops** » Thu Jul 25, 2013 9:53 am

yeah its correct mate lol,
just got the wiring details through, so off out in the garage in a bit to wire up the fans to the ecu and put the settings into the ecu to trigger it

stevieturbo · Post by **stevieturbo** » Thu Jul 25, 2013 10:18 am

Should just be one wire. From ecu to relay.

Post by **Coops** » Thu Jul 25, 2013 10:35 am

yeah it is mate earth trigger wire to relay

richardpope50 · Post by **richardpope50** » Thu Jul 25, 2013 12:56 pm

stevieturbo wrote:Normally a fan switch would be towards the top of the radiator ? Or in the top hose itself ?

... but the best place is in the rad output hose at the bottom as then it is sensing the actual cooled water temp and adding the fan if the rad is not cooling enough.

Post by **Coops** » Thu Jul 25, 2013 2:45 pm

The MS ecu is now coupled up to the cooling fan relay, and the car is sat happy just over half on temp gauge,
fans set to come on at 90C go off at 88C that sound ok temp wise for the fans???

stevieturbo · Post by **stevieturbo** » Thu Jul 25, 2013 5:50 pm

richardpope50 wrote:
stevieturbo wrote:Normally a fan switch would be towards the top of the radiator ? Or in the top hose itself ?
... but the best place is in the rad output hose at the bottom as then it is sensing the actual cooled water temp and adding the fan if the rad is not cooling enough.

You ultimately want to cool the engine. Water temp coming out of the rad is less important unless it isnt sufficiently cold to cool the engine.

But as long as engine cooling is kept in check, that's all that matters.

Coops wrote:The MS ecu is now coupled up to the cooling fan relay, and the car is sat happy just over half on temp gauge,
fans set to come on at 90C go off at 88C that sound ok temp wise for the fans???

That will depend on your normal engine running temperature. What does it sit at when cruising at say 50-60mph ?

Then set the fan to come on maybe 3-5 degrees above that temperature and then of 2-3 below your chosen temperature.

Ian Anderson · Post by **Ian Anderson** » Thu Jul 25, 2013 6:09 pm

stevieturbo wrote:
richardpope50 wrote:[quote="stevieturbo"

You ultimately want to cool the engine. Water temp coming out of the rad is less important unless it isnt sufficiently cold to cool the engine.

Stevie
That is interesting as I was advised the opposite.
Give the car a quick blast and the water entering the rad may spike upwards. Why would you at that stage want the fan to come on? You may be going at 40 mph and the normal airflow will do the job.
Now position the switch near the outlet and that spike will not be seen, the fans not turn on etc.
the only time you need the fan to be on is when the water exiting the rad is getting too hot and hence needs cooled

Ian