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Discussion Starter · #1 ·
Hi everyone I’m back with a 2004 Mini Cooper having problems with the cooling fan,I’ve bought a resistor separate too the fan just wanted to know the wires I splice into are both red one thick one small is the thic one the slow speed thanks for your help
 

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I did this last week - R53 Fan
There is a diagram in this thread.
Thick Red - hight speed fan
Thin Red - low speed fan
I used a 100w 0.33ohm resistor - it gets bloody hot.

Before I carried out the mod I double checked the low speed fan was not working by unplugging it and putting 12v onto the connector pins, sure enough high speed was OK Low speed was not.
 

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Discussion Starter · #3 ·
did you cut any of the wire because when I connect the resistor ,the way it shows on a few images online only the fast speed works thanks for replying
 

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just connect it as per the original if the same style?
 

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Discussion Starter · #6 ·
The way I connected it was I attached wires to the resistor,put one wire to the thick red wire and the thin red wire on the car I cut and connected the resistor to the cut wire on the car side of the 3 pin plug
 

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I didn’t touch the wiring on the fuse box side of the plug, the female side.

I cut the thin red on the radiator side of the plug - the male side - I then insulated the end that goes toward the radiator, this goes to the resistor, which has become open circuit, then to the fan.

The cut end coming out of the plug connects to one end of the new resistor, the other end is spliced into the thick red wire. The thick red wire is not cut.

The way the 2 speed fan works is that the relay in the fusebox sends 12v down either the thin red wire or thick red wire depending on what the ECU decides the fan speed needs to be. Both thin and thick wire ultimately go to the same positive terminal on the fan, the thin wire has the resistor in series which drops the voltage making the fan spin slower.
All the mod has done is replace the resistor, and used the thick red wire to connect to the fan. If the ECU has determined the fan speed needs to be low then the thin red cable is live and the thick red is not.
If the fan works on high speed it will also work on low speed if you have the circuit correct.
Hope this makes sense.

I have a drawing I made to put in my cars service folder detailing the mod I can send if you like? But it’s on my NAS drive in my office and I’m not there until tomorrow. Let me know.
 

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I bought a complete new fan. It's just plug and play. Plus I'm not fixing up old compnents.that could still fail.

My fan has two connectors, pre May 2003, so couldn't be bypassed.
 

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Discussion Starter · #9 ·
The way I connected it was I attached wires to the resistor,put one wire to the thick red wire and the thin red wire on the car I cut and connected the resistor to the cut wire on the car side of the 3 pin plug
I didn’t touch the wiring on the fuse box side of the plug, the female side.

I cut the thin red on the radiator side of the plug - the male side - I then insulated the end that goes toward the radiator, this goes to the resistor, which has become open circuit, then to the fan.

The cut end coming out of the plug connects to one end of the new resistor, the other end is spliced into the thick red wire. The thick red wire is not cut.

The way the 2 speed fan works is that the relay in the fusebox sends 12v down either the thin red wire or thick red wire depending on what the ECU decides the fan speed needs to be. Both thin and thick wire ultimately go to the same positive terminal on the fan, the thin wire has the resistor in series which drops the voltage making the fan spin slower.
All the mod has done is replace the resistor, and used the thick red wire to connect to the fan. If the ECU has determined the fan speed needs to be low then the thin red cable is live and the thick red is not.
If the fan works on high speed it will also work on low speed if you have the circuit correct.
Hope this makes sense.

I have a drawing I made to put in my cars service folder detailing the mod I can send if you like? But it’s on my NAS drive in my office and I’m not there until tomorrow. Let me know.
hi thanks for replying that’s how I’ve got mine still no slow speed ,not sure where to go from here thanks again 👍
 

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Discussion Starter · #10 ·
I didn’t touch the wiring on the fuse box side of the plug, the female side.

I cut the thin red on the radiator side of the plug - the male side - I then insulated the end that goes toward the radiator, this goes to the resistor, which has become open circuit, then to the fan.

The cut end coming out of the plug connects to one end of the new resistor, the other end is spliced into the thick red wire. The thick red wire is not cut.

The way the 2 speed fan works is that the relay in the fusebox sends 12v down either the thin red wire or thick red wire depending on what the ECU decides the fan speed needs to be. Both thin and thick wire ultimately go to the same positive terminal on the fan, the thin wire has the resistor in series which drops the voltage making the fan spin slower.
All the mod has done is replace the resistor, and used the thick red wire to connect to the fan. If the ECU has determined the fan speed needs to be low then the thin red cable is live and the thick red is not.
If the fan works on high speed it will also work on low speed if you have the circuit correct.
Hope this makes sense.

I have a drawing I made to put in my cars service folder detailing the mod I can send if you like? But it’s on my NAS drive in my office and I’m not there until tomorrow. Let me know.
That would be great for the drawing cheers 👍
 

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Discussion Starter · #12 ·
That’s exactly hoW I did my wiring still nothing bought another resistor thought it could be that nothing, the relays are both working power going to the red wires when upto temp,iknow there’s nothing wrong with the fan as it comes on
(only on fast)it’s very strange,when I put a link wire across both red wires it works as I should
fan comes in at 105 degrees is it safe to keep the link in?thanks for replying
 

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That is the type of resistor I used.
What value is the resistor you used? The only thing I can think of is that the value is incorrect so the voltage reaching the fan though it is too low, even to make the fan turn at low speed. Can you measure the voltage at the resistor?

On another thread on the forum on this topic someone has wired in a link as you suggest and reports it has worked OK, although its not something I'd do long term.
 

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Discussion Starter · #15 ·
Hi this is the specs
33R 5% 100W aluminium clad wirewound power resistor from the Arcol HS series. High quality and stability. Designed for heatsink mounting using thermal compound to achieve maximum performance. Manufactured in line with the requirements of IEC115 and MIL18546. Suitable for pulse applications.
is it the right one thanks again for your help
 

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^^^^ Wot 'e said.

In resistor nomenclature the "R" is where the decimal point would be.

R33 - 0.33 Ohms

33R - 33 Ohms
 
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