Why does cooling fan go off with ignition?
 

I've noticed during the hot weather that the engine cooling fan is coming on more - obviously really.

However, why does it go off when the ignition is switched off? Surely it should stay on irrespective of the ignition if the engine needs cooling down?

Would it not be a good idea to source the location for the wiring for the cooling and wire it to a constant +ve feed to ensure the engine is cooled properly - ala R5 GTT for example.

The fan on my 220 turbo used to stay on as well. I'm sure there must be a reason why the Subaru one doesn't, but buggered if I know it...! :)

Perhaps because as the engine is not running the water pump will not be either, making it a worthless exercise having the fan on??? :confused:

I don't know much about these things though! :)

Matt

That doesn't explain why my 220 did though... :confused:

Because it was a Rover? ;) :D

Good point. Probably wasn't actually meant to... :D

I guess but then it still works when the engine is off but the ignition is on.

Does anybody perceive any dramas if I wired the cooling fan to a constant +ve?

It may take longer for the engine to get up to temp. Unless you have overheating problems then don't really see the need for this, leave it in control of the car!!

Matt.

On most cars Edd that is exactly how the electric fans work. Not exactly sure about the Scoob, but maybe what happened with my car last Sunday can shed a little light.

I took my JDM MY99 wagon for a bit of spirited driving ;) When I stopped first the turbo timer kept the engine running for about a minute while it cooled down. The engine cut and initially so did the cooling fan. However about a minute later the cooling fan kicked in again. There is usually some hysteresis in cooling fan control, kick in at say 95 deg C and cut out when the temp drops to say 90 deg C. Maybe when the ignition is cut at between 90 & 95 deg C the fan cuts too. With my car on Sunday I guess the heat soak, heat coming of brakes, turbo etc was just enough to send the coolant temperature back over that upper threashold again.

Not sure if I'm right, but it sounds convincing ;)

What I meant was to wire the fan to a constant +ve so when the ignition is off the fan will still operate until the temp sensor turns it off. At the moment the fan stops when the ignition is off, its never come back on no matter how hot the engine.

Can't see any harm in making the feed to the cooling fan +ve so if the engine is hot enough for the fan to come on in the first place the fan will stay on until the senor turns it off rather than the ignition.

If the engine is off the water pump is obviously off too so water circulation will be minimal. If you wire the fan to a constant +ve will it not run continuously until the battery is flat? Just a thought...

I'm a auto electrician in a peugeot garage but have a scooby myself (alot more fun !).The cooling fan if wired to a constant + feed may cause the battery to go flat if the fan switch is on the thermostat housing as with the engine off there won't be any water movement so that rad water temp will drop due to the fan blowing through the rad but up at the thermostat housing the water will still be hot and keep the fan on , if the fan switch is fitted to the rad then when the rad cools with the fan the switch will turn the fan off and battery should not suffer .
So basicly depends where the rad switch is fitted on how well it ill work .
We used to wire carb cars to constant feed to help prevent fuel evapouration during hot weather using a heat sink temp switch to turn the fan on and a 12 minute timer relay , this is an option you could use via an additional timer relay and wiring .

My fan comes on for the air-con. Turn off the air con and off goes the fan goes off.

The fan comes on and off while the air con is on to condense the hot liquid back to a gas for the compressor to pump as if it's still in a liquid form the compressor would hydraulic , also the air con has a pressostat switch which depending on the pressure in the air con circuit will turn the fan on at a low speed , second stage high speed and third stage cut the compressor out and keep fan's on at high speed .
I've not checked out my scooby yet (only had it a month !), but that's an older peugeot set up !

On my old fords (Rs Turbo & Cosworth - I know), the fan would stay on after the engine was cut off - I was always told to run the engine after a 'spirited drive' until the fan did cut in so the fan would move the still, hot air out of the engine bay.

However it was more than likely cr@p wiring....

A simple mod is to place a fan switch and turn it on 2 minutes before stopping the car....

;)

Nuno