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MG MGF Technical - Question on side louvre inlet fan

The drivers side inlet louvre has a small intake fan behind it, does the fan run only when a sensor operates it ? if yes, where is the sensor located ?
Do you know if the fan freewheels under forward motion or is it stationary until a sensor cuts in ?
I know if you switch on the ignition it doesn't start the fan automatically thus pulling in ambient air.
J McvGregor

The fan is activated by the engine compartment heat sensor - I forget the exact amount but do remember that it is lower for the MPi than the VVC - it also runs on when the engine is switched off if it is activated.

The sensor is up quite high by the drivers side hinge to the boot lid but further into the engine bay.
Ted Newman

Here's some info I found in the workshop manual:

Engine bay ambient air, warning light switch ON - 90C.

Engine bay fan switch, operating temperature ON - 75C, OFF - See below,

In addition to the normal water cooling system an air
cooling system is provided for the engine
compartment. This is achieved by a fan mounted in
the right hand side intake ducting, blowing cool air
over the engine.
The temperature of the engine compartment is
monitored by the ECM via signals from an ambient
air temperature sensor. The sensor is mounted on
the engine compartment header panel, directly
above the inlet manifold.
When a temperature of 75C (85C vvc) is reached in
the engine compartment the ECM switches the fan
temperature of 65C (75C vvc) is reached before the
pre-set time has elapsed the fan will switch off
If the engine compartment temperature rises to
130C, the ECM will illuminate the engine
compartment warning light in the instrument panel.
This will warn the driver of abnormal engine
compartment temperature or that a fault exists in the
system. When the temperature drops below 110C
the warning light will extinguish.
The fan will operate for up to eight minutes after the
ignition has been switched off to attain the required
engine compartment temperature.

"End quote

Branko/Ted, thanks for the comments.
I can't see the ambient sensor in the engine compartment is there a picture of it that could perhaps be e mailed to me? All I can see are two wires coming directly off the fan motor into the EMU.
My initial thoughts are that with the operating range of the fan system, very little cool/cold air will enter via that particular louvre, I expect something like at least 50% of the area is blocked off with the fan motor etc.which seems to be a design pity.
Is it possible for the EMU to be altered to operate the fan to come on at lower temperature thus bringing in more air thus more cold air to get into the air filter etc. etc.
I'm also very surprised that the system only indicates a "problem" in the engine compartment when the air temperature reaches 130 degrees C ( 270 degrees F approx)I would have thought that at that temperature wiring would start to degrade and all sorts of problems ensue - but hey I'm no designer!!
Any advice you can give would be appreciated - all this is because I'm trying to build a hybrid air intake system on the cheap !!
John Mac


Very little of the air used by the engine comes through the side vent - in fact they are extremely poor at pushing air in.

Most of the air rush comes from under the car when the car is moving - the fan is just there IMHO to provide air whilst the car is static or slow moving.

I dont have a picture of the sensor I am afraid.

Ted Newman

Dieter's website to the rescue!

The sensor page is here:

The picture showing the location of the enginebay air temperature sensor is this one:

Rob Bell

Found it - thanks.
Still wonder about those temperatures according to Branko's manual though.
John Mac

>>> Any advice you can give would be appreciated - all this is because I'm trying to build a hybrid air intake system on the cheap !! <<<

Been there, done that.

As my new ECU doesn't support a fan in the engine bay, I used a third party IC-board with very few electronic components on it, attached it to a live wire (so it can be actvated even when the car is switched off) and to the fan. Now I can manage the temperature when to turn the fan on and off again (hysteresis sp?) from in the cabin.

IC board and some cables must be around 10.

The new sensor is installed on the same spot as the old one.


John, what design were you considering for your intake? Realistically, the fan doesn't really pull anywhere near enough air to be useful for an intake system - but rather, it would simply get in the way.

Erik, good to hear that you've got the engine bay temperature control sorted now! Great work :o)
Rob Bell

Simple really probably been done dozens of times before :-
Replace existing air filter with new K&N performance one.
Remove existing air box and cut min 2" hole in back near the bottom.
Fit 2"x 90 degree UPVC bend with backnut into opening.
Run 2" tube and flex. into left hand air intake.
(this will increase air in by 100%)
Modify existing air intake to lower position.
See if EMU can be altered to control existing louvre intake fan at different temperature range,thus bringing in air earlier.
And that's it really - certainly not high tech ( and I didn't want the "roar" of an Induction set up)

For some reason your link is "Page not available"
John Mac


Damm!!, had typed out some more info to add, but my PC had a hernia! ie can supply a diag if required etc, etc...

Anyway, looks like more people have come to the rescue just in time.

However, the cooling system seems to be designed reasonably well as it uses the radiator water cooling as a standard feature. Then if things get a little hot the twin thermo fans kick in to cool the radiator which cools the engine. Then if it gets even hotter the engine bay sensor and ECU lend a helping hand by turning on the engine fan. While the car is moving the natural airflow will also help as well.

So, what's the actual problem and/or what are you actually trying to do with the cooling system?, if I may ask. :-) ??



It's not the engine water cooling system I'm "playing" with, it's the "air cooling" around the engine bay - where the present carburation air is sourced from. As you know at present, all combustion air enters the engine from the single 44mm dia. air inlet tube to the filter box. High engine bay and ambient air temperature means less oxygen content therefore poorer combustion.
I don't know if export models (you in Australia) have a different inlet arrangement because of your higher on average ambient air temperatures to ours ?
Clearer now ?

John Mac

That is exactly the reason, please read earlier threads regarding air filters, why the K&N system is highly regarded, there are others such as the ITG or the Taipan of course.

By taking the cold air straight from the left hand air intake by way of a tube into the filter.

Read the other threads on air filters and enjoy the knowledge.

Adrian Clifford

I did start an earlier thread on filters and got some very useful information. I have a K&N on order that should arrive next week.
Silly little question - Iv'e removed the existing "paper" panel filter and want now to take out the plastic filter box - how do you undoe the two "bolts" on the nearside holding the box to the brackets, they appear to be hard plastic, but don't have any cross top for a screwdriver or any sides for a spanner !! are they simply push out ? I dont want to cut them in case I need to revert back sometime in the future. Those that changed to the Induction kit would know.- Thanks
John Mac


Ok, now you've made it clearer what you are trying to do.

The air intake is setup here is Aus as in the UK.
We do however experience much higher summer temps, but I would expect the ECU would adjust the mixture of air/fuel as required for different conditions. ie , cold air, hot air etc.

I would have thought that the air flowing thru the intake to the filter and then to the inlet manifold would not have much time to be significantly heated up by the engine bay air temps.



I agree with what you say on inlet air temperature. With today's temperature of -1 C I don't think we have too much to worry about. It's when we get our scorching hot summers I'm preparing for !!!!!!!!!!

John Mac

John, Erik's working link: (note that the closing parenthesis gets included in the address line when you click on the embedded link).

So the idea of the fan is to lower the ambient engine bay temperature, so to reduce heat soak into the filter box?

I'd suggest that this is probably not the most effective way to go. The reason I say this is because even if the cooling fan comes on at a lower temperature, it may have only marginal benefit in terms of maintaining a significantly lower temperature. I think a better result could be achieved either by insulating the intake system by lagging it or by replacing the existing fan with one of a more efficient design (I don't have any suggestions as to suitable replacement fans, but I'd have thought there must be alternatives).
Rob Bell

Hi John

I added a K&n aircleaner using the standard
air box but I removed the resonace chamber.
it's that giant box made of plastic which sit below aircleaner. You might have to hack saw and swear alot to remove it. I them ran a 60mm scat hose( crush proof aircraft hose) from left hand air intake.
Car preforms and sounds great. A larger dia
Say 70 /80mm might improve thing even more.
hope this helps
M L Dippenaar

This thread was discussed between 23/02/2005 and 28/02/2005

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