Mini R56/R58/R59 Cooling Fan Problem. Think I am going mad..

[Megaflow]

This started out as an air conditioning problem, it didn't work.

I took it to Kwik Fit for a free check and they confirmed it had no leaks, vac'd it out and regassed it. But it still didn't work... so they didn't charge me!

They said the reason it doesn't work, is the cooling fan does not come on with the A/C when the car is stationary.

Some test's has confirmed that the cooling fan in isolation works, on both speeds. But, when I feed 12V into the control wire terminal of the relay socket for fan speed 1 it does not. Fan speed 2 does work with the same test.

This suggests a broken wire somewhere.

A continuity check between the fan end of the wire and the fuse box confirms the wire is fine, but a continuity check between the bottom of the fuse box to the top of the fuse box, produces nothing. Nada, nicht, nothing.

How can that be? Unless the fuse box is knackered, but how can a fuse box fail?

Edited by Megaflow on Saturday 28th June 17:41

[GreenV8S]

Megaflow said:

a continuity check between the bottom of the fuse box to the top of the fuse box, produces nothing. Nada, nicht, nothing.

I can't quite picture what you're testing there. Are you saying the wire isn't connected to the corresponding fuse holder? Have you proved that you're testing at the correct fuse holder?

[Megaflow]

GreenV8S said:

I can't quite picture what you're testing there. Are you saying the wire isn't connected to the corresponding fuse holder? Have you proved that you're testing at the correct fuse holder?

Yes the wire is not connected to the corresponding socket, it is a relay in question not a socket. Yes, it the correct relay.

Interestingly there is a lot of videos about Mini fuse box repairs, most seem to be about interior fuse boxes, but have fuse boxes moved in from being inanimate objects?

Edited by Megaflow on Sunday 29th June 08:23

[GreenV8S]

Megaflow said:

Yes the wire is not connected to the corresponding socket, it is a relay in question not a socket. Yes, it the correct relay.

That sounds like an internal fault in the fuse/relay box. I suppose you could remove and inspect it to see what the problem is. That seems potentially a lot of work. No idea how valuable or precious the car is, but you also have the option of bodging it by adding a separate relay.

No idea what your last sentence was trying to say.

[21TonyK]

I might be misunderstanding the problem but a dodgy fan resistor is a common problem, ie. it only works at certain speeds etc

https://www.autodoc.co.uk/nrf/17882286?utm_medium=...

ETA: yep, think i misunderstood, cooling fan not heater/aircon fan

[Richard-D]

21TonyK said:

I might be misunderstanding the problem but a dodgy fan resistor is a common problem, ie. it only works at certain speeds etc

https://www.autodoc.co.uk/nrf/17882286?utm_medium=...

ETA: yep, think i misunderstood, cooling fan not heater/aircon fan

This was going to be my suggestion too. Worth a look in case a wiring diagram has been misunderstood. The Aircon fan is also an engine coolant fan on most cars so not a reason to discount it.

[Megaflow]

GreenV8S said:

Megaflow said:

Yes the wire is not connected to the corresponding socket, it is a relay in question not a socket. Yes, it the correct relay.

That sounds like an internal fault in the fuse/relay box. I suppose you could remove and inspect it to see what the problem is. That seems potentially a lot of work. No idea how valuable or precious the car is, but you also have the option of bodging it by adding a separate relay.

No idea what your last sentence was trying to say.

Sorry the last sentence was meant to say Mini fuse box, and there are repair video's of the internal fuse box on line.

Apologies all, I typed a response to this Saturday, but it doesn't seem to have posted.

This is the wiring diagram for the fuse box/cooling fan:


The cooling fan and resistor have been tested in isolation and function correctly.

When I feed 12V into terminal 87 for relay R10 2, the cooling fan runs. When I do the same test for terminal 87 for relay R10 1 it does not work.

That would suggest a wiring problem between terminal 87 of R10 1 to the cooling fan. But when I disconnect the plug that contains the wire from the fan to R10 1, I have continuity, which suggest the problem is internal to the fuse box.

Very confusing.

[jeremyc]

Your wiring diagram shows a component between where you have fed the +12v (R10 1 pin 87) and the motor (possibly internal in M10 1) - this is not present in the other path you have tested (R10 2 pin 87).

Any idea what this might be - it could be the cause of the failure.

Is there continuity (or a resistance) between M10 1 pins 4 and 2?

[Megaflow]

jeremyc said:

Your wiring diagram shows a component between where you have fed the +12v (R10 1 pin 87) and the motor (possibly internal in M10 1) - this is not present in the other path you have tested (R10 2 pin 87).

Any idea what this might be - it could be the cause of the failure.

Is there continuity (or a resistance) between M10 1 pins 4 and 2?

It is not very clear, but I believe the component you are talking about is the resistor to create the second fan speed, that is mounted to the cooling fan, little green cylinder on the image below. When I test the cooling fan in isolation it was at the cooling fan connector, so included this resistor, and it worked as it should.



I haven't check continuity between pins 4 & 2, I'm not sure what that would tell me. The cooling fan works when powered directly at pins 4 & 2. If there was an internal short of the cooling fan, then surely it would fail that test?

[jeremyc]

Megaflow said:

I haven't check continuity between pins 4 & 2, I'm not sure what that would tell me. The cooling fan works when powered directly at pins 4 & 2. If there was an internal short of the cooling fan, then surely it would fail that test?

Did the fan run at different speeds when directly powered at pins 4 & 2?

Also, did you remove the relay when applying +12v at R10 1 pin 87? I'm wondering if there could be an internal fault in that relay that is providing a lower resistance path to ground.

[Megaflow]

jeremyc said:

Megaflow said:

I haven't check continuity between pins 4 & 2, I'm not sure what that would tell me. The cooling fan works when powered directly at pins 4 & 2. If there was an internal short of the cooling fan, then surely it would fail that test?

Did the fan run at different speeds when directly powered at pins 4 & 2?

I don't believe so, but I powered it with a power probe, so that will limit current being feed to the fan.

jeremyc said:

Also, did you remove the relay when applying +12v at R10 1 pin 87? I'm wondering if there could be an internal fault in that relay that is providing a lower resistance path to ground.

Yes, the relay was removed when I fed the power into R10 1 pin 87.

It would appear I can buy a second hand fuse box for £15-20, so my current plan is to find the right part number fuse box, repeat the same test as the current fuse box and potentially to use it as a sacrificial lamb to work out how they can be taken apart, so I can then try and figure out what is wrong with the current one. Or, if it passes the test the current one fails, I might just bang it in.

[Megaflow]

Update: I have found the part number of the fuse box and bought another fuse box of the same part number for a whole twenty of your finest pounds.

That’s cheap enough just to check I am not going mad and metering out correctly, it also gives me another to compare with.

Watch this space.

[Megaflow]

Fuse box has arrived and there is no continuity on this one from the pin I checked on the current fuse box to the relay terminal either.

Which says I have the wrong terminal, but then why does the wire connected to the terminal I am checking meter out to the fan



The terminal on the underside of the fuse box that the red/blue wire that is supposed to connect to terminal 87 of the relay, is actually connected to terminal 30. Which makes me wonder if I have got the right wire & terminal. But the fact the continuity checks out to the fan suggests I have.

This is very odd, I need to check under the fuse box again to check there isn’t another red/blue wire, but I am 99% sure there isn’t.

Edited by Megaflow on Wednesday 2nd July 21:24

[GreenV8S]

Megaflow said:

why does the wire connected to the terminal I am checking meter out to the fan

Typically, relays and fuses are installed on the positive side of each circuit, and the negative side of each component is grounded. That means you have a circuit from the positive wire for one component, through that component to ground, back through any other component and back to that other component's positive supply to the fuse or relay that controls it. Whether your meter reports that circuit as connected would depend on how much those components conduct and how much resistance the meter will accept as a connection.

I can't see your fuse box or exactly how you're measuring connectivity, but is it possible you're simply mistaken about which fuse/relay that wire is supposed to be connected to? It would explain away a lot of the symptoms you're seeing.

[Megaflow]

Yes and no.

After posting the above last night I have done some more testing. The wiring diagram above clearly shows the power coming into terminals 30 & 86 via 2 x 40 amp fuses.

I did some poking around last night and the wiring diagram is wrong… about right for Haynes… the power actually goes into terminals 87, confirmed with a continuity check from the fuse to terminal 87, which explains why that meters out to several terminals except the one I thought it should do.

I did work out which terminal was the switch supply to the fan, but I have forgotten over night, at the weekend I’ll feed that 12v and see what happens, I am expecting the fan to run and I am going to be back to square one…



PS: anyone know a reliable source for wiring diagrams? I don’t mind paying, I paid for the Haynes one, and that is crap…

[GreenV8S]

What you're describing sounds very strange. Are you sure you have the correct relays fitted and are numbering the terminals in the relay socket correctly? There are two common relay terminal layouts (Type A and Type B) which swap the positions of terminals 86 and 30. If you're assuming the 'wrong' layout then you'll get some very strange results.

[Megaflow]

Yep, they are BMW Tyco OE relay’s and the pins are clearly marked on the underside, and both fuse boxes meter out in the same way.

Also, I should probably add for clarity, the A/C worked when we bought the car, so this is a problem that developed recently, so it is not someone messing around with the relay’s or wiring because they haven’t been touched until now.

[ian332isport]

Just going back to basics for a moment. What exact year and model are we looking at here?

I do have access to proper BMW wiring diagrams.

Edited by ian332isport on Saturday 5th July 21:10

[paul_c123]

Megaflow said:

Yes and no.

After posting the above last night I have done some more testing. The wiring diagram above clearly shows the power coming into terminals 30 & 86 via 2 x 40 amp fuses.

I did some poking around last night and the wiring diagram is wrong about right for Haynes the power actually goes into terminals 87, confirmed with a continuity check from the fuse to terminal 87, which explains why that meters out to several terminals except the one I thought it should do.

I did work out which terminal was the switch supply to the fan, but I have forgotten over night, at the weekend I ll feed that 12v and see what happens, I am expecting the fan to run and I am going to be back to square one



PS: anyone know a reliable source for wiring diagrams? I don t mind paying, I paid for the Haynes one, and that is crap

Alldata

[Megaflow]

ian332isport said:

Just going back to basics for a moment. What exact year and model are we looking at here?

I do have access to proper BMW wiring diagrams.

Edited by ian332isport on Saturday 5th July 21:10

Hi Ian.

Thank you for the offer. After working out the wiring diagram was wrong I used the second fuse box, which only cost twenty quid, to meter out the terminals and work out what went where.

That enabled me to retest the cooling fans circuits from the relays by energising them with a power probe. That confirmed both cooling fans work, at different speeds.

This afternoon I went to the a/c compressor to energise it with 12v and see if I could get the fans to recognise that and come on, and in doing so found this:



Corroded earth connection.

Bingo!