Cooling fan help

[sworks]

Been reading some of the cooling fan posts but got a bit confused after reading so many. What is correct operation as i have only noticed 1 speed on my car. The fan cut in today when needed and sounded quite loud, when it cut out again i turned the air con on and it seemed to be the same speed. Is this normal as i thought the aircon speed would be higher? Sorry if this is a stupid post thats been covered but it's been a long day.

[T-Cut]

Assuming the engine coolant temperature is 'normal' or lower, the fan should operate continuously at 'slow' speed when the engine is running and the A/C system is switched to Auto. It should stop shortly after switching to Econ. With Auto on, the fan should not exhibit an on-off pattern every 30 seconds or so. If it does, it's faulty. The 'high' speed is basically for emergency engine cooling or if the A/C system becomes overheated. If your car is a late or facelift model, it will have a 2-speed fan. Earlier models are 3-speed. As to whether yours is running at 'slow' or 'high' will depend on the above criteria. A 'high' speed fan sounds like a hovercraft. The 'slow' speed is an audible hum, which can just about be heard when driving.
TC

[sworks]

It does sound like a hovercraft, but i was confused as i thought low speed for basic cooling and fast speed for emergencys and air con. Sounds like i am only getting fast speed? 53 plate pre facelift

[T-Cut]

It does sound like a hovercraft, but i was confused as i thought low speed for basic cooling and fast speed for emergencys and air con. Sounds like i am only getting fast speed? 53 plate pre facelift

No, A/C normally requires only the slow speed fan. It will switch to high speed if the refrigerant system overheats, which it will if the low speed side is faulty. That's why it cycles on-off as the system cools, then reheats. Very bad for the A/C compressor. You may have a faulty 2-speed motor. Look through the front grill and between the fan blades in the 2 o'clock position. You may see a 3" long aluminium resistor mounted on the fan framework. If so, this has probably failed.

TC

[sworks]

Thanks for the info - if it's working ok so far, maybe it just hasn't got hot enough for the fast speed :confused:

[T-Cut]

maybe it just hasn't got hot enough for the fast speed :confused:

Possibly. And at this time of year it may not do so. Leave car standing with engine running and A/C on. Keep an eye on the temp gauge and listen/watch for the high speed to kick in. If it does all's OK.

TC

[sworks]

Thanks for all your help :bowdown:

[Steven D]

Good afternoon all,

After having read of all of the posts concerning cooling fans, type, upgrades, etc.. I'm afraid to say I'm even more confused than before....

I new to the 75 fold and have owned my 03 1.8T for little over a month. I bought it with a very comprehensive (and suitably expensive) 3 year warranty.

The observations I have made are :-

a) When aircon is switched on the fan unit is also activated (at what speed I don't know but it's not turbine loud)
b) When aircon is switched off it deactivates (except during point (c) below)
c) When the car has been run for a while and I park up it seems that the same fan is sometimes activated. This switches off when the ignition is switched off.
d) Sometimes when the car has been run and parked with engine running and no fan present, if I then switch on the aircon the fan starts but does not stop by swtiching the aircon off again. It then stays on until I turn off the ignition.
e) The car operates always within the normal temperature range - i.e. bang on midway on the temperature guage
f) I have left the car on tickover from cold for about half an hour until the temperature reads normal and no overheating or fan cuts in. The only time the fan seems to activate (when not in aircon mode) seems to be when it has been out on a run, even on cold days like yesterday. It seems to be prevalent when parking/reversing up or sitting in traffic.

Is this me just being paranoid or should that low speed fan only just work then the aircon is switched on ?.

Any help would be greatly appreciated.

Thankyou all, in advance.

Steven

[kaiser]

I think it all sounds fine. The reason why it may start after you park the car, is heat soak. When you switch the ignition on again, the heat has soaked into the water around the sensor, and not been moved away because the engine is stationary. It will soon clear when the engine runs, and the fan will stop.
As for the temperature gauge sitting on normal, it will do that anywhere between 75 and 115 degrees.
Just keep an eye on water level and fan motor, as a matter of routine.

[Steven D]

Thankyou very much for your quick response and from so far away !.

My main concern was that even after a small blast (1 mile) in relatively cold conditions the fan would sometimes come on, even though the temperature gauge was sitting mid-way. Sometimes the fan starts as I drive up my estate road, never mind when the car is actually stationary/reversing into the drive. Does the 1.8T run naturally hot ?.

It also bugged me that when the engine is cold I can switch on and off the AC with merry abandon but when the engine is warm, once it's switched on the fan stays on.... For how long I don't know. That would be my next investigation.

I think I'm being a little paranoid - or maybe a lot...

Cheers

Steven

PS Sorry - just wanted to clarify that the fan does not seem to come on during normal driving - only when the car is slowed to park or stopped to reverse, etc...

[GreyGhost]

PS Sorry - just wanted to clarify that the fan does not seem to come on during normal driving - only when the car is slowed to park or stopped to reverse, etc...

If I have this right, the fan should only operate at all if the vehicle is doing less than 30MPH. Otherwise airflow through the rad will cool it sufficiently.

[T-Cut]

I also believe you are describing the normal behaviour of the 2-speed fan fitted to all 1.8/1.8T models. It's significant that you have only experienced the car's cooling system during the colder part of the year. When the weather warms up next year, you will probably experience other features, like its high speed operation.
It will be useful for you to know the type of system you've got. Does it have the slow speed resistor system? Knowing this will allow you to plan for any possible failure that may occur in the future.
You can gain a clearer picture of how the 2-speed system works by reading just the parts in the post http://www.the75andztclub.co.uk/forum/showthread.php?t=1371 as it relates to the 1.8 engine. Forget all the other variations and try to get an understanding of the specific system you have.
As to the apparently strange way your fan works, remember that the A/C condenser, which is also cooled by the fan, is actually mounted just in front of the engine radiator, from which it can absorb some heat by radiation. The A/C condenser is like a radiator, but runs at much lower temperatures, so a bit of additional heat can have a big effect.
If you've not so far heard the high speed turbine-like fan, I don't think you have anything to worry about.

TC

[Steven D]

Thankyou Gents,

That gives me great comfort. You are indeed correct, the fan only comes on when the car is either stationary or 'creeping' about, i.e. parking, reversing, etc.. and even then it's only rarely. I have not noticed the fan when driving above 30mph and I have listened for it intently !!.

I will read the 2-speed fan thread. I don't seem to have that resistor that has been mentioned at 2.00.

Again, my many thanks. I will keep it monitored closely.

Now all I need to do is sort the creaking passenger window and the rattle behind the dash which disappears with varying temperature. I may have to venture behind that glove box and check out the BCU. Problem is that I have the touch of an elephant and the ethos of "if it's not broken don't fix it" definitely applies to me....... I always end up thinking "why didn't you just leave it alone".

Again many thanks. This truly is a great place to be !.

[T-Cut]

I have not noticed the fan when driving above 30mph and I have listened for it intently !!

I don't think the fan has any road speed related control. It's all based on fluid temperatures or A/C pressure. The ram effect at 30mph just happens to provide enough cooling to prevent the thermal trip. In very hot weather, you'll probably have to drive faster to get the same effect.

TC

[Steven D]

Yes, sorry - I didn't mean to intimate I'd taken your 30mph comment as meaning some kind of 'switch' !. I'm happy that it does not seem to have (yet ?) taken on the characteristics of some of the problematic ones I have read about within the threads. I do understand though that the 2-speed unit is less problematic. Funnily enough, this is the first car I've ever owned (at the tender age of 38), all my previous ones being company cars. It's become something of a obsession of a owning a car....... I'll get some photos up soon after I've finished Zymol-ing it to death. Beautiful car, though.