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Old 1st October 2019, 09:17   #1
BRG75
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Default How to identify a cooling fan type

I would like to thank SD1too, who has vetted this content for accuracy, and added a few comments for completeness.

Whilst this site contains a wealth of information on cooling fans, may I suggest that for newcomers (or nearly new, like myself) some foundation information might help to put the detailed information into context.

I hope that this is not reinventing the wheel, but I was unable to find the basics in one place, and found myself having to piece it together.

TEXT

All Rover 75 / MG ZT's have 2 fans.

The FIRST simply circulates hot / cold air within the cabin, and is better described as a blower fan. It is located behind the dashboard.
This article is NOT about this fan, but it is mentioned, in order to eliminate the sound it makes, and a potential wrong diagnosis.


The SECOND fan is located in front of the radiator, and is a recognised problem area, although with the passage of time, it was, and still can be, made reliable.
The fan has two similtaneous functions, engine cooling and air condition operation. This is of assistance in basic fault diagnosis (excluding the very few cars without air conditioning)

Early cars were fitted with either a 2 speed fan (K series 1.8) or a 3 speed fan (KV6 & Diesel)

The different speeds on these fans were controlled by relays, which switched in additional brushes.
The brushes wore out, particularly the "common" brush, and were (in their day) considered unrepairable.
However, since around 2009, and still the case today, replacement brush sets are available. These appear to have varied in quality / cost, but the brushes from at least one supplier have stood the test of time.

MG Rover then changed the design, so that the fan speed was changed by the switching in or out, of a resistor. Unfortunately, the original resistor (silver coloured) was inadequately specified, resulting again in fan failure, but with different characteristics.

Inevitably, when the cars were current, a failed fan could have been "repaired" by:-

a) Replacement of the correct item, shall we say factory sourced.
b) Replacement of either the correct or incorrect item, say breakers yard sourced.
c) Changing from a brush to a resistor speed switched item.
d) Changing to an aftermarket fan, such as Kenlowe.

There is no known introduction / cut off date for the factory change, but it seems that both old and new design fans were factory fitted around 2002 and 2003. There are also reports to suggest that this continued to the end of production.

Regarding replacement brushes for the earlier units, it is not known (to the writer) if both 2 and 3 speed versions used the same brushes.

October 23rd - An article today, with photographs, strongly points to the brushes being the same dimensions.

However, following a phone call yesterday, a set of 4 brushes (3 speed) are available from "Engineering Carbon Products" who still list them on their website.
If the 2 speed units do indeed use the same brushes, they will now sell a set of 3.
If the brushes are different, they can still manufacture replacements from a pattern, or dimensions.

It should also be noted that when the resistor fans came out, all variations were fitted with 2 speed units.

In summary, it is essential to know what fan is presently fitted to your car, before reading up on the (very detailed) test procedures to be found on this club site.

Early 2 speed (3 wires, take off front bumper to identify)
Early 3 speed (4 wires, take off front bumper to identify)

Later 2 speed (2 wires, resistor visible at 2 o'clock, through radiator grille)

Any Silver resistors should be replaced with a Gold one.

I hope that this is of assistance

BRG75
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Last edited by BRG75; 23rd October 2019 at 07:04.. Reason: Later information has come available
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Old 23rd October 2019, 08:23   #2
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Hi Mike.
All the fans use four brushes, 1.8 2.0 2.5 & diesel, not all the late cars came out of the factory with 2 speed units, therefore your (It should also be noted that when the resistor fans came out, the all variations were fitted with 2 speed units.) will not be true I have seen 2004, 54, 05, 55, and 1 2006 with a four wire 3 speed fan, all on diesel cars.

I will be tacking a diesel fan off today, which I will open up at a later today or possibly tomorrow.

This thread will help the member have all the information to work out which fan they may have on their car nice idea Arctic.
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Old 23rd October 2019, 08:49   #3
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All the fans use four brushes ...
Hi Steve,

What about a 2 speed, 3 wire motor fitted to a 1.8 engine? I thought that used only three brushes?

Simon
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Old 23rd October 2019, 09:00   #4
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Hi Steve,

What about a 2 speed, 3 wire motor fitted to a 1.8 engine? I thought that used only three brushes?

Simon
Hi Simon.
All the fans have four brushes as you can see from the one I opened Monday

1

2

3

4

All four brushes were used & burned .
5
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Old 23rd October 2019, 09:10   #5
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Thanks for the pictures Steve. I have two questions about them.
  1. I can't see a brush in the holder at the eight o'clock position but I do see the braid. Had the brush worn to nothing?
  2. To which colour wire is the fourth brush connected please?
Thanks Steve.

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Old 23rd October 2019, 14:05   #6
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Thanks for your response, Arctic.

I think that your experience of early fans on later cars, ties in totally with what SD1too advised me of, when he vetted my original text. I covered it in para. 9, reproduced below :-

There is no known introduction / cut off date for the factory change, but it seems that both old and new design fans were factory fitted around 2002 and 2003. There are also reports to suggest that this continued to the end of production.

My thought was that the factory may well have been using up old / new stock.
I didn't mention that in the final draft, as it was only supposition on my part.

I should add that I'm a newbie as far as maintaining a 75 is concerned.
Indeed it is because I suspect that I have issues with my car's fan assembly, that I started to research the subject, resulting in the "how to" that I wrote; for my own benefit, initially.

Regards

Mike
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Old 23rd October 2019, 20:37   #7
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Originally Posted by SD1too View Post
Thanks for the pictures Steve. I have two questions about them.
  1. I can't see a brush in the holder at the eight o'clock position but I do see the braid. Had the brush worn to nothing?
  2. To which colour wire is the fourth brush connected please?
Thanks Steve.

Simon
Hi Simon.
Yes the brush had worn to nothing and was burnt off.

The forth brush is connected to the purple I think.

These photo's are from 2014 which may help more as they are clear.
1

2

3
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Old 24th October 2019, 09:00   #8
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Thanks for the pictures Steve but I'm still not clear how it works with four brushes. Do you have a spare board that you could send to me?

Simon
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Old 24th October 2019, 14:47   #9
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Thanks for the pictures Steve but I'm still not clear how it works with four brushes. Do you have a spare board that you could send to me?

Simon
Hi Simon.
Drop me a PM with your full name & address then I will post out these two boards for you, a 1.8 & a four wire 3 speed diesel both have burnt out.
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Old 24th October 2019, 17:35   #10
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Thanks Steve. PM sent.

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