Radiator fans description and operation

[Keith]

I have scanned and OCR'd this from my Electrical manual so there could be some mistakes I have also corrected the info where we know the manual to be wrong. This is what is supposed to happen:-

COOLING FAN DESCRIPTION

K1.8
Cooling fan operation on Rover 75 is controlled by the Engine Control Module (ECM), which receives signals of engine coolant temperature from the Engine Coolant Temperature (ECT) sensor. The cooling fans operate at two different speeds, depending on engine coolant temperature. The cooling fans also operate after the ignition has been turned off to control rising engine temperatures after the engine has stopped running.

KV6
Cooling fan operation on Rover 75 is controlled by the Engine Control Module (ECM), which determines cooling fan operation with the help of information received from the following sources:

. The ECT sensor.
. The Automatic Transmission Control Unit (ATCU) via the CAN-BUS.
. The air conditioning trinary switch.

The cooling fans can operate at high, medium, or low speed depending on the information received by the ECM. If the ECM receives contradictory fan speed request signals, it will always choose the highest speed requested. The cooling fans also operate after the ignition has been turned off to control rising engine temperatures after the engine has stopped running.

M47R
Cooling fan operation on Rover 75 is controlled by the Engine Control Module (ECM). The ECM determines cooling fan operation with the help of information received from the Engine Coolant Temperature (ECT) sensor, and the air conditioning trinary switch (if fitted). The ECM delivers a pulse width modulated (PWM) signal to the cooling fan assembly. The frequency of this signal is determined by engine coolant temperature, and determines whether the cooling fans operate at low, medium, or high speed

If air conditioning is requested, the cooling fans automatically start operating at low speed. If a subsequent request is made for a higher fan speed (i.e. the engine temperature has risen) this higher fan speed request will always override the lower fan speed request.

continued on next post

[Keith]

OPERATION

K1.8
General
Feed from the positive battery terminal (CO192) is supplied to fusible link 4 and the main relay (C0632) on an R wire. Both are located within the engine compartment fuse box. Fusible link 4 (CO574) supplies a constant battery feed to the low and high speed relays housed within the cooling fan assembly (C0019) on a N/U wire.

The main relay (C0576) is controlled by the ECM (C0913) on a W/K wire. When energised, the main relay provides a feed to the cooling fan assembly (C0019) via fuse 4 of the engine compartment fuse box (C0575) on a Y/U wire.

The ECM constantly monitors engine coolant temperature via the ECT sensor. The ECM (C0914) provides a feed to the ECT sensor (C0169) on a K/G wire. As engine coolant temperature rises, the resistance of the sensor falls. By measuring the voltage returned from the ECT sensor (C0169) on a K/B wire, the ECM (C0914) can determine engine coolant temperature.

Engine Running
With the engine running, the cooling fan can operate at either high or low speed, depending on engine coolant temperature. If the ECT sensor registers a temperature of between 98 °C and 104 °C, the ECM (C0913) energises the low fan speed relay within the cooling fan assembly (COO88) on a U wire. The energised low fan speed relay is then able to supply a feed to the cooling fan motor, which is earthed (COO88) on a B wire!

If the ECT sensor registers a temperature of between 105 °C and 112 °C, the ECM (C0913) energises the high fan speed relay within the cooling fan assembly (COO19) on a U/R wire. The energised high fan speed relay is then able to supply a feed to the cooling fan motor, which is earthed (COO88) on a B wire

The ECMswitches both cooling fan relays off if the ECT sensor registers a temperature of 98 °C or lower.

Engine Stopped
If the ECM registers an engine coolant temperature of above 112 °C while the engine is not running, it will energise the main relay within the engine compartment fuse box. The main relay (C0575) is then able to provide the cooling fan high speed relay (C0019) a feed on a Y /U wire. The high speed relay (COO88) is provided an earth path via the ECM (C0913) on a U/R wire. The energised high fan speed relay supplies a feed to the fan speed motor, which is earthed (COO88) on a B wire.

The cooling fan motor is now able to operate at high speed until the ECT sensor registers a temperature of below 112 °C.

Note: The cooling fan will only operate at high speed when the engine is not running.

KV6
Feed from the positive battery terminal (C0192) is supplied to fusible link 4 and the main relay (C0632) on an R wire. Both are located in the engine compartment fuse box. Fusible link 4 (C0574) supplies a constant battery feed to the cooling fan (C0019) on a N/U wire. This feed is supplied to the low, medium, and high fan speed relays located within the cooling fan assembly.

The main relay (C0578) is controlled by the ECM (C0371) on a W/K wire. When energised, the main relay provides a feed to the cooling fan assembly (COO19) via fuse 4 of the engine compartment fuse box (C0575) on a Y/U wire.
The ECM constantly monitors engine coolant temperature via the ECT sensor. The ECM (C0371) provides a feed to the ECT sensor (C0373) on a K/G wire. As engine coolant temperature rises, the resistance of the sensor falls. By measuring the voltage returned from the ECT sensor (C0373) on a K/B wire, the ECM (C0371) can determine engine coolant temperature.

The ECM controls the operation of all three relays according to the signal it receives from the ECT sensor. If the ECT sensor registers an engine coolant temperature of between 96°C and 100°C, it triggers the ECM (C0371) to provide an earth path for the low fan speed relay (C0088) on a U wire. The energised low fan speed relay drives the fan motor at low speed. The cooling fan assembly (C0088) is earthed on a B wire.

If the ECT sensor registers an engine coolant temperature of between 102°C and 106°C, it triggers the ECM (C0371 ) to provide an earth path for the medium fan speed relay (C0088) on a U/Y wire. The energised medium fan speed relay drives the fan motor at medium speed. The cooling fan assembly (C0088) is earthed on a B wire.

If the ECT sensor registers an engine coolant temperature of between 108°C and 112°C, it triggers the ECM (C0371) to provide an earth path for the high fan speed relay (C0019) on a U/R wire. The energised high fan speed relay drives the fan motor at high speed. The cooling fan assembly (C0088) is earthed on a B wire.

Air Conditioning Request
If air conditioning is requested, Edit:- the cooling fans will automatically operate at _low_ speed, even if the coolant temperature is below 96 deg. C.. If an air conditioning request is received by the ECM when the cooling fan is running at low speed (i.e. the engine coolant temperature is between 96 °C and 100 °C) the ECM will increase the fan speed to medium. If the engine coolant temperature rises above 108 °C the cooling fans operate at high speed as described previously.

ATCU Request
If a request is made by the ATCU via the CAN-BUS for more automatic gearbox cooling, the ECM controls the fan speed as described in the 'Air Conditioning Request' section.

M47R
Feed from the positive battery terminal (C0192) is supplied to fusible link 4 and the main relay (C0632) on an R wire. Both are located in the engine compartment fuse box. The main relay (C0576) is controlled by the ECM (C0603) on a B/K wire.
If the ECT sensor registers an engine coolant temperature of between 100°C and 105°C, the ECM (C0331) will send a PWM signal on a U/R wire to the cooling fan (C0019) requesting low fan speed. The PWM converter within the cooling fan assembly then provides a feed to energise the low fan speed relay. This allows a battery feed from fusible link 4 (C0574) to flow across the low fan speed relay (C0019) and power the cooling fan motor and low speed. The cooling fan motor (C0088) is earthed on a B wire.

If the ECT sensor registers an engine coolant temperature of between 106°C and 111°C, the ECM will send a PWM signal to the PWM converter requesting medium fan speed. The PWM converter will then energise the medium fan speed relay within the cooling fan assembly. This allows a battery feed from fusible link 4 (C0574) to flow across the medium fan speed relay (C0019) and power the cooling fan motor at medium speed. If the ECT sensor registers an engine coolant temperature of between 112°C and 119°C, the ECM will send a PWM signal to the PWM converter requesting high fan speed. The PWM converter will then energise both the low and high fan speed relays. This allows the battery feed from fusible link 4 to power the cooling fan motor at high speed.

Taken from RCL 0311ENG

[Keith]

CDT Cooling strategy
The ECM controls cooling fan operation for the engine, automatic gearbox and A/C condenser. With the ECM controlling cooling fan operation, it can adjust injection duration and timing to compensate for additional engine load imposed by the alternator during cooling fan operation. The ECM can request one of three fan speeds depending on coolant temperature, EAT ECU and A/C requests. These fan speeds are:
Low: 250 rev/min.
Medium: 800 rev/min.
High: 1750 rev/min.Priority will be given to the highest fan speed request. When A/C is requested, fan speed is set to low, unless the EAT ECU or ECT requires a higher fan speed. If the cooling request circuit of the trinary switch is open the fan speed is then set to medium. High speed fan operation will be selected by one of the following conditions:
Engine temperature is greater than 119 °C (246 °F).
EAT ECU request for increased cooling.The ECM achieves fan speeds by sending a 140 Hz PWM signal to a PWM converter located within the fan relay module. The PWM converter is connected to three relays, also located within the fan relay module, and determines which relays to energise by the duty cycle of the pulse:
13%: Relay one energised to give low fan speed.
40%: Relays one and two energised to give medium fan speed.
86%: Relays one, two and three energised to give high fan speed.Note for the V6 and CDT three speed fans the high speed relay does not switch a third +12V supply to the motor as shown in the wiring diagrams instead it switches in a second ground brush in parallel with the normal ground brush.
This explains why when most motors fail only high speed works as the normally used ground brush on the Black wire wears out prematurely leading to no low or medium speeds.

Later Vehicles (V6 and CDT)
Later vehicles were all fitted with a two speed fan, these benefited from two ground brushes being wired in parallel to extend their service life. The two speeds were then controlled via a large (visible through the grill) external resistor mounted on the fan cowl. It would appear that the resistor has been known to be a weak point again if it fails leading to operation at only one speed. The resistor is however easily replaceable and a 100W .47 ohm resistor from somewhere like Maplins is believed to be suitable but may need mounting on a heat sink.

Note For the CDT the fan will run when AC is selected with or without engine running but for the petrol version the engine must also be running.

Aircon behaviour and Ambient Temperatures,
It was originally believed that when Aircon was selected the fan always came on at the lowest speed this is not correct and operation is determined by the temperature difference between the chosen ATC setting and the outside temperature if that difference with an outside temp of 12.5 degrees is more than approx 10 degrees C than fan will not run. 10 degrees here is used as an example as this value may increase dependant on outside temp i.e at zero degrees the difference may be even higher.

E.g
It is +12.5 in my car at the moment
I stepped my AC up from my normal 20 degrees (car is a CDT so no need for engine running) when it got to 23 degrees fan stopped step back down again and fan restarts at 21 degrees.

[Keith]

Warnings
The centre metal boss of the motor is not earthed and if earthed the motor may run so always take suitable care.


The fan blades are not designed to be taken off regularly they can be reused with care if removed carefully but should be inspected for stress cracks around boss and the blades, a new one is cheaper the a replacement Aircon Condenser!

[Keith]

Repairs :-

Motor
It is possible to dismantle a faulty motor by carefully bending and straightening the tabs on the back and removing the back plate. Normally it becomes immediately obvious that the brush attached to the black wire has worn down to the point where it loses contact and hence the motor stops, often though the other brushes are also jammed by carbon deposits in their brass holders. A replacement brush and a clean up of the holders, commutator etc will normally return many thousands of miles of life to the motor but a supplier of brushes has not yet been found so cannibalising old motors is currently the only source.
Please note a source for the brushes is now available, see this link:- http://www.the75andztclub.co.uk/forum/showpost.php?p=365598&postcount=73
Some people have had limited success flushing the brushes in a fully assembled motor with WD40 although to be able to get the WD40 to where it matters i.e the back, the Motor should be removed as spraying through the grill is not adequate.

Be careful when dismantling and reassembling the motor not to dislodge the front bearing as any sideways movement could cause the fan to foul the shroud, dropping one as I did is not to be recommended!

Relays
Rarely one of the two or three Relays in the fan control box might fail in service
All the relays in the Rad fan control box are made by Tyco, they are Form A (on these quoted docs)
if the contacts look badly pitted replacing them whilst doing the motor is a good idea.

The relays are the same in Diesel and V6 Petrol I need verification re those in the 1.8

Big relay is V23134-B52-C642
http://catalog.tycoelectronics.com/TE/bin/TE.Connect?C=1&M=BYPN&PID=123704&PN=V23134B%20%205 2C642&I=13 (http://catalog.tycoelectronics.com/TE/bin/TE.Connect?C=1&M=BYPN&PID=123704&PN=V23134B%20%2052C642&I=13)
and http://relays.tycoelectronics.com/datasheets/134.pdf

The two little relays are both V23073-B1005-A302 typical, I can't find them directly on the Tyco website but a google brings up this!
http://www.growtech.cn/admin/ProMgt/...5144750730.pdf (http://www.growtech.cn/admin/ProMgt/Files/2006325144750730.pdf)

Almost any relay of a similar rating could be used in the petrol version as the box has lots of space but in the diesel the correct form factor is required to avoid having to wire them externally as the circuit board is designed to connect directly to the relay coils

Under bonnet fuse box Relay
This is a standard Relay and for testing could be swapped for any other similar coloured one in the car it only powers up the coils (and PWM circuit for the CDT) in the fan control relay box not the fan motor itself. if none of the relays in the fan control box can be heard clicking check this relay first.

Note The motor is hard wired to an large Fuseable link, expect smoke before that fuse ever blows!

Now the bit that matters a link to Howto get the Bumper off.

http://www.the75andztclub.co.uk/forum/showthread.php?t=204

The following posts contain some pictures of the various control boxes and Fan internals etc

[Keith]

Below are several interesting photos sent to me by Elise.
They are from a 1.8 and two later (2004/2005) CDTs all are later versions of the Fan Motor assemble featuring a dirty great resistor to provide the lower speed

The motors although physically similar have had their brush connections redesigned internally the motors still use four brushes but they have now been paralleled up in pairs to increase their life

Note these motors if bought individually will not be direct swaps with earlier vehicles’ without a bit of rewiring in the relay box but a complete assembly with relay box and resistor will be a direct swap as long as somewhere can be found on the original fan shroud for the resistor which must be in the airflow or it will not last long.

You will notice only two wires going to the motors one is a permanent live from the main fuseable link the other is a switched ground.

Each Motor control box now only has two relays both switching to ground one switches the ground wire of the motor directly to ground the other via the resistor.

Pros
Extended Brush Life leading to a longer lasting motor

Cons
Now only two speed
Using a dirty great resistor is wasting electricity and therefore fuel
The resistor seem to have replaced the brushes as being a point of failure

Picture 1 2005 CDT relay wiring

http://www.midnightphotos.co.uk/userimages/full/13/5326.jpg(No longer available)

Picture 2 2004 CDT relay wiring

http://www.midnightphotos.co.uk/userimages/full/12/5328.jpg(No longer available)

Picture 3 1800 relay wiring

http://www.midnightphotos.co.uk/userimages/full/9/5329.jpg(No longer available)

Picture 4 Resistor wiring, please click on image for a bigger picture where it is easy to see where the cables go

http://www.donottumbledry.co.uk/mg_img_bin/5330_small.jpg (http://www.donottumbledry.co.uk/mg_img_bin/5330.jpg)(No longer available)

Pictures 5 and 6 the front and rear of the revised brush design (rear image has been flipped so left matches left of picture 5) this is from a very burnt out motor

http://www.midnightphotos.co.uk/userimages/full/8/5331.jpg(No longer available)

http://www.midnightphotos.co.uk/userimages/full/3/5332.jpg

[Keith]

Some more Pics
Difference (height and wattage only) between 1.8 (on left) and CDT V6 motors

http://www.midnightphotos.co.uk/userimages/full/9/5719.jpg

Warning label on Fan Blades

http://www.midnightphotos.co.uk/userimages/full/12/5720.jpg

CDT Relay box with PWM Circuit

http://www.midnightphotos.co.uk/userimages/full/9/5270.jpg

CDT complete asembly, the joins in the wires are not repairs these are how they are assembled at the factory.

http://www.midnightphotos.co.uk/userimages/full/1/5269.jpg


CDT Brushes, the short brush is the one going to the Black wire and this motor failed due to the wear on this Brush.


http://www.midnightphotos.co.uk/userimages/full/10/5272.jpg


KV6 relay Box

http://www.midnightphotos.co.uk/userimages/full/3/5263.jpg

[Keith]

And again for these of you the did not read the above :) a link to how to get the Bumper off.

https://www.the75andztclub.co.uk/forum/showthread.php?t=204

Feel free to ask questions and if necessary the answer will then be added to the above and the thread kept as tidy and as relevant as possible

[MartinW]

Not sure if it's polite to do so, but for those with a Mk1 MG ZT KV6, you can look here (http://www.brit-cars.com/mg/zt-zt-t/bumper-removal-fan-motor-replacement.html) for a complementary "how-to".

There are some minor differences from the 75 as I discovered whilst using the excellent notes in the link above. But the main difference I would like to add is that there is a simpler removal to the bonnet slam panel by removing the cables from their block rather than undoing the bonnet locks themselves.

Many thanks for the information and inspiration on here to give this job a go myself!

[Keith]

Symptoms
One that seems to puzzle people On Off On Off...........

Firstly remember correct behaviour (unless it is freezing cold outside, see above posts) is:-
CDT, AC on fan will run constantly at low speed with or without engine running.
Petrol, AC on fan will run constantly at low speed but only with engine running.

Sometimes people ask why the fan is going on and off every few seconds.
This is because firstly the low speed has failed, whatever the cause, brushes or the resistor.

The reason the fan cycles is because the Trinary switch in the AC pipe detects an increase in refrigerant pressure as the currently un-cooled refrigerant gets hotter and hotter.

The Trinary switch does not know the fan is not running so once the pressure rises to a high enough level the Trinary turns the fan on to high speed.

Then you get the full fan cooling effect over the Condenser whereas before there was nothing, result refrigerant is quickly cooled pressure drops Trinary switch disengages the high speed fan which because it is duff stops instead of continuing at the lower speed, pressure begins to rise and so on in a cycle.

Hope that makes it clearer

[Keith]

Jules has written an excellent resistor replacement Howto for those with faulty two speed fans.

http://www.the75andztclub.co.uk/forum/showthread.php?t=4638

[Jules]

Keith hit Nail on the head so to speak with the Trinary switch explanation ie: with 30 second ON OFF syndrome!
It will shorten the life of the AC compressor too if left like this too long, I've had to change a couple to date.

And I suspect this fault condition does not show on Keiths diagnostic T4 either??

Could be why main dealers say "oh they all do that" as their T4 is not aware of this fault condition.

Keith does the Trinary over pressure switch activation not trigger a fault code?

[Keith]

No it does not as the operation of the switch in this respect is assumed to be "normal" i.e it is doing what it designed to do as there could be all sorts of reasons why the Trinary might kick in especially on a very very hot day

[Fraser Mitchell]

I just cannot believe that the brushes on this motor are unique to the R75; it just doesn't make sense, so there MUST be brushes available out there somewhere ! Probably for an electric lawnmower !!

Photo shows the name 'Siemens' on the motor cover. If there is a part number on there, this could enable the brushes to be identified.

[Jules]

My sentiments entirely Fraser, of all the 1000's of electric motors in the world the 75 cooling motor must have generic brushes!!

Hoovers, drills, compressors, lawnmowers, cooling motors off other cars, pumps, extractors, heater motors............any advance?

[ANDY 545]

Edit by Keith
The following post from Andy may help if after buying a later two speed motor for the CDT you find it still does not work when you turn on the AC

Hi there
Well my car is a 52 plate 03 CDT now the problem Ive got is this, last week had the aircon running in traffic but kept hearing a noise like something engaging then disengaging so I investgated.I found that the fan was not running ay low speed so I thought heard about this one look on the forum.
Now with my fan I span it and started going great but two days later same situation except this time smelt burning like a electric motor dying. Got home had a look nut in middle of fan very very hot so I thought motors gone, got a new motor from ex mg rover dealer (HAD THREE IN STOCK) I know I could have got it cheaper if I shopped around but I had along trip planned and I don't like driving with out a engine cooling fan(TRAFFIC JAMS).
Got the fan part number PG000110, spent most other day fitting it.Now when I fitted it I tested the engine cooling thats Kay could test the air con because the temp sensor went down to -30 pressed for time put the car back together,now temp sensor is back to normal still no air con fan.
Now in the fan packaging there is a modification note (WHICH I BELIEVE I NEED TO DO) and that is:

THIS FAN MOTOR MAY NOT OPERATE ON SLOW SPEED ON LATER MODEL CARS
SHOULD THIS BE THE CASE THEN PLEASE FOLLOW THE MODIFICATION BELOW

CUT THE GREY WIRE AT THE RELAY BOX (FLUSH AGAINST THE RELAY BOX)THEN SPLICE THE REMAINING (LONG) GREY WIRE INTO THE RED/BLUE STRIPED WIRE

[Keith]

Here we go troops
Brand new brush measurements.

First thing to note a new one is not radiused at the armature end, instead the end is cut square and is slightly serrated and is obviously designed to quickly wear down to a radius during bedding in.

Brush Length 22mm
Brush Width 9.6mm
Brush Thickness 4.6mm
All four long edges have a very slight chamfer

Copper braid exits centre back of one of the wider sides and is about 1 to 1.5mm thick and about 2mm wide (not easy to measure really)! Braid needs to be capable of carrying say 40-60A and needs to be at least 35mm long.

The Brush, or rather two of them, note how much of the braid has been messed up getting them unsoldered!

http://www.midnightphotos.co.uk/userimages/full/4/7056.jpg

[Jules]

Cor Keith I'll give you a million quid for those beauties:drool4:

[JohnDotCom]

That looks like its not pure copper braid there Keith to go that bad.
Normally with enough temperature and Watts in Iron surely if copper, it should be cleaner and easier to remove?
Don't suppose it will be easy to fit a new one, or even get them out.
:bowdown: No criticism meant or intended Keith, just wondered why, perhaps just Coated.
...and Jules offer seems good for your retirement Fund :D

[Keith]

I had to apply a lot of heat the get it unsoldered hence the discolouring they may be using a higher temperature solder!

[JohnDotCom]

So that means that changing them would not be an easy DIY job.

[Keith]

Anyone trying to contact Siemens (the more the merrier as we will get an answer one day) might find the following worth adding to their email

"The Motor in question has the following information
Siemens Canada
772-65430-01
13.5V
As per picture on the right here http://www.the75andztclub.co.uk/forum/showpost.php?p=13175&postcount=7"

[tomcat22]

Hi,

if anyone is interested, I got two brand new sets of these:

http://www.technikline.com/assets/big/lf1008.jpg

Size is a little bigger (5x10x24mm), but they will fit to our radiator fan motor.
Hope this helps...

TOm

[Keith]

They look very close Tom thanks
I will copy this post to its own thread for the purpose of discussions about suitability costs availability etc and then bring the conclusions here.

[Keith]

Questions that really belong in their own threads are being asked in this one so I have closed the thread as I want to ensure only specific and relevant info as and when it becomes available is posted here

For all you signed up members (i.e. guests can't see all the Howtos) here is a link to my Kenlowe Howto

http://the75andztclub.co.uk/forum/showthread.php?t=109061

Brushes for the 3 speed fans are available from http://www.engineeringcarbonproducts.com/index.php

See thread.
http://www.the75andztclub.co.uk/foru...8&postcount=72

Well done and thanks from all the members with three speed fans.