Hi there, looked through all the pages, is there a "master" diy instructions for the external resister fix?

 

what year car you have?

 

I tried to be the 500,000th reviewer but was a few hours late. Truly amazing that people continue to read - and respond to - this thread.

 

Did you get a reply? I'm having this problem with my 2003 R53.

 

The 2003 R53 has the relay on the fan and two plugs. You cannot easily move the resistor off the fan like the 2004 and later R53s. What I settled on was a new fan, TCY from RockAuto and changed out the resister assembly for the much more robust one from Dorman/Detroit Tuned. It is still going strong after many year as the resistor is a thick coil rather than the flimsy green wire wound...

After you've done it a few times, you can change out the fan in a half hour.

///Rich

 

So, would putting a new stock fan fix it (for a while at least)?

According to Detroit Tuned, it looks like this unit should fix my problem.

 

Yes it is! it's the only unit we sell and install because it works correctly every time and it is all Stainless Steel so it will not fail again!


Chad
Detroit Tuned

 

2006 R53 here with the single fan connector.

I just finished this mod today to get my low speed fan working again. I ordered the Arcol gold resistor from Amazon, attached it to the engine mount with some machine screws after tapping some holes, and used some Arctic Silver (leftover from a computer project) for the thermal connection.

I used 12 ga wire from the resistor to the two red wires on the fan side of the fan connector, and used two 12 ga quick splice connectors from Home Depot to connect the wires up.

Both high speed and low speed fans are fully tested and working now. Thanks everyone for the hard work in figuring out an easy solution to this engineering failure.

 

Very good !
That sounds like hope for me.

I have a 2003 R53 , tested the fan with 12v directly on to the connector and only the highspeed fan kicks on so i guess the resistor is dead.
Also have the single fan connector.

Will it work again by putting a 0,33 ohm 100 w resistor after the connector?
-Looks like this ? : thin wire -> resistor -> to thicker wire (highspeed wire) ? .
-Will the highspeed fan work properly when it kicks in or the resistor will melt or something and set car on fire ? haha

My A/C is also not kicking in, is it because of the 1st stage fan not going on ? i've read that they are connected to eachother.

Many thanks !

 

You should check the AC relays in the engine compartment fusebox, the AC clutch and also the pressures on the compressor. There are instances where with no low speed the pressure builds up to the point that the system purges through the relief valve.

 

Thanks for your reply, i did check and tested the relays for the AC they are good.

The ac clutch does not come on as the revs don't go up, they should go up right ?
One thing to mention is that i can't get cold air from the vents , it is hotter than outside temperatures.
Engine is not overheating, around 92-96 degrees celcius.

I am going to check the pressure on the AC after the 1st stage fan resistor mod.

 

I found my '05 MCS had the low speed fan issue, spliced in the 100W 0.33Ohm resistor and mounted it up front by the condenser, Now my Marshall aftermarket temp gauge reads 202-205F regardless of the outside temp-Perfect!, and it cross references to my OBD temperatures as well. Its too bad that MINI decided to use a temp gauge that seems to have a Log curve response so you can't see any changes from ~180F to 240F. I long suspected Tigger had an issue with the fan, it wasn't until I put the Marshll gauge in that I could confirm it, Many thanks to Chris Lamb for the fix!

 

I've tried to read the most of this thread before asking stupid questions, but I can't find a similar case to mine.
My Cooper 2002 has the 5 wires to fan assembly. 1 red for low speed, another red for high speed, brown for ground and 2 extra for the relay for the high speed fan.

My 1st stage fan and AC are not working. I've managed to test 1st stage by connecting the 1st stage red wire direct to car battery and found that it is working, also tested 2nd stage and got it working.
I've swapped relays and they are working, checked fuses in engine fuse box and are ok, even the one under the engine fuse box.
Checked fuses inside the car and also ok.
I've checked for continuity between the the fusebox and the low speed wire and it is working - tested with multimeter on the pin where the relay goes and the low speed red wire in fan assembly.

I'm puzzled on why it won't work. I've even checked the pins that activate the relay for the 1st stage, and the ECU is providing voltage as I've managed to mesure current when activating AC , Ive got values between 12 and 14V.

Anyone could have a clue or giving me a hint on something that I might be doing wrong.

thank you in advance

 

It's not the relays. There is a wire wound resistor on your fan. If the fan is OEM, it is green and about 3/4" in diameter. You can take the fan out and replace the relay pack with the Dorman assembly which has a resistor that will not burn out. In my opinion, that is the best option. You can also get a Dorman aftermarket new fan with a more robust resistor.

This thread is old and long and hard to follow at times. But the resistor fix will only work for a one plug fan and not the 2002 or 2003 Mini's. BUT for cars 2004 or later, it's a great mod.

///Rich

 

 

Not trying to necropost but since I am in the process of fixing the low speed fan on my mid year (6/2002) R53 I thought I'd post some info I've not seen in this looong thread and ask a question.

First I have the same arrangement of connectors and wiring as the poster quoted. The large connector contains 3 pins, 2 for power and 1 for return which are connected via red and black wires to the resistor/relay box mounted on the fan housing itself. The smaller connector has 2 pins leading to the same resistor/relay box via a red and a green wire. This (small) connector controls the relay which in turn switches the high speed circuit to the fan on and off. I believe I've seen pics in this thread showing the pin arrangements but I may post another myself just so people can spend less time search through this looong (but highly informative) thread.

The resistor/relay "box" is held to the fan housing via 2 8mm bolts. There's a sealed box that contains the relay while the (green) resistor and thermal switch are visible upon unbolting. If you're replacing the resistor with one like that shown above (or one from another vendor) you'll have to pry open the sealed box as one of the wires to be cut is very short, forcing you to add the splice between it and the replacement in the sealed box. There's a Youtube vid on removing the fan and I recommend anyone replacing the resistor and thermal switch view it.

Right now my Mini is sitting on jackstands in the chilly garage awaiting a myriad of fixes, among them was replacing the bad resistor. Aside from the fan not coming on at low speed, one can tell if the resistor is blown if you're handy with an ohmmeter by measurement at the big connector. If you test for continuity between the ground pin and the proper power pin you should see a low ohms reading. This circuit path is through the wiring, resistor, thermal switch and fan motor. If you measure using the other power pin you'll see an open circuit due to the de-energized relay. Need I say you should have the car off, not running. If you're unsure of which power pin is which, measure both with respect to the ground pin. One measurement should be an open, the other low ohms. If you get this result your fan problem likely lies elsewhere. If both paths measure open circuit then your resistor needs replacing (or perhaps the fan itself).

The JPG below shows depicts the circuit paths above. I note it contradicts at least one similar diagram in this thread but I'm really really sure mine is correct.
(Note: due to my junior status here I can't yet post the JPG but I will when I'm allowed)

I don't have a good way to accurately measure the currents for each path, someone has posted them previously in this thread. I can say that I have the fan running off a car battery and it runs at about 2700 RPM via the high speed path with my battery measuring 11.7V under the full load. With a new (URO) resistor and thermal switch in place, the same fan runs at 2040 RPM with the battery voltage now at 11.9V under the lesser, low speed load. And yes that battery is not super good ! Measuring the voltage drop across just the new green resistor I see 2.95V, and across the resistor plus thermal switch ... 3.15V. So if the new green resistor is the same 0.33 ohms as the uber wattage resistor being used in the fix, that places the low speed current in the 9A territory. If I can figure out a better way to measure the currents (high and low speed) tomorrow I'll post them.

To estimate my adhoc wiring and connection losses I measured the voltages from the negative battery terminal to the nearest-to-the-fan+ point at the end of the resistor. With the battery being now more discharged I measured 11.6V across the battery itself and 11.35 at the resistor in high speed mode. So that's a loss of 0.25V through (my battery to big connector wiring plus the stock Mini wiring harness to the relay and then also through the relay itself). I will assume the same amount through the return side wiring, meaning the 11.35V measurement implies about 11.1V at the fan + and - terminals. In the low speed mode I measured 11.7V across the battery and 8.3V at the "fan end" of the resistor. At the other end of the resistor+thermal switch I measured 11.5V. That's a loss of 0.2V through (my high side adhoc wiring plus the Mini harness). Assuming the same loss through the return side wiring means the 8.3V measured is really 8.1V at the fan terminals. That's a fan motor Kv of 243 or 251, close enough that I call the measurements sufficiently consistent to make sense.

FWIW the resistor got to a measured temp of 220F fairly quickly upon running in low speed mode. The resistor was not in the fan airflow, just sitting in my 56F ambient garage.

So now for the question. Is there still any interest in coming up with another fix, one for us owners of earlier Minis, that might be applicable to other, later models too ? Specifically I mean a fully electronic speed controller that reduces the fan speed in low speed mode by PWM'ing the supply to the fan in that mode. Seems to me that it would be less wasteful than the present "dropping resistor" method and, if done properly, more reliable ... a "one and done" fix. My thinking is that a simple old school linear type 555 timer (not a CMOS type) with some filtering/protection on it's supply voltage could control a MOSFET as a high switch. Perhaps heat sink the FET and Bob's your uncle ! Now if I have the spare parts that I think I have, I may protoboard something up and give it a whirl with the thought that my replacement resistor is likely to go bad again and I'll want a better solution at that time.

BTW did I mention how looong this thread is ?

 

Hello NAM, still have my 2003 R53.
Fix still working!
Have fun

 

I have two 2006 MCSs with the fix still working as well. I did replace one resistor once. Thanks again Chris Lamb!

 

Chris

I have recently bought a mini One and its having overheating issues, realised the fan isnt working which is probably one of the causes, so thanks for the simple fix recommendation - and thanks to NAM as it seems to be the only forum that actually covered the subject so well.

 

Hi MacsR53Mini,
I tried the PWM method a couple of weeks ago. A 555 timer driving a solid state relay (mosfet unit with all the control hardware built in & mounted in a convenient heat sink potted unit). Check out Cat #SY4086 at Jaycar.com.au or here
https://www.jaycar.com.au/solid-stat...ching/p/SY4086

This is a 100A unit which will handle the fan load with ease providing you heatsink it properly. I mounted it on the engine mount behind the LHS headlight like most people in this thread. It mounts easily & the aluminium mount is the perfect heat sink. The relay is switched by a basic 555 PWM circuit running at about 50hz. The solid state relay is a bit limited by the on/off time of 0.5sec, so you don’t want to switch it too fast. By using a variable pot on your 555 you can vary the on/off pulse width...
https://howtomechatronics.com/how-it...-555-timer-ic/

Don’t forget your free wheeling (or fly back) diode. I left this out on the first attempt thinking that it was built into the relay. I was wrong and shorted the Fets on the relay after about 10 minutes. Because of the way the fan is wired your free wheeling diode will need to be able to handle the full fan load, not just the half speed load, I.e. at least 50A. The cheapest & easiest option is to use a 35A (or higher) bridge rectifier, about $7. Connect the negative side of your rectifier to ground, connect the positive to the output of the solid state relay (or fan positive). Don’t connect the AC terminals of the rectifier, put some heat shrink over them to protect them. This will give you 2x35A capacity (70A) for the free wheeling diode.

All of this will cost you around $80. A fair bit more expensive than the resistor option, and probably not as reliable in the long run. FET’s really don’t like voltage or current spikes and aren’t the best things to use in automotive environments without a lot of voltage & current protection, which would drive the cost up further.

In the end I opted to go with 2 bridge rectifiers in series in place of the resistor ($14). This gives a voltage drop which is independent to motor load (unlike the resistor), so that the fan supply voltage will not vary if the fan load varies. I get about a 4 volt drop across the rectifier pair, and a 10.2 volt on the fan. Remember voltage = speed for a DC motor. The fan current at this voltage is around 13-14 amps, which will give about a 50-60W consumption in the rectifier diodes which has to be removed via the heat sink.

 

Well done to all the folks who contributed to this thread to help solve the problem.
One item I noticed may not have been covered too well is the high speed relay sticking (for those who have the first gen models like me with the high speed relay mounted in the fan housing). Many have noticed that a quick tap turns it off & the general fix appears to be replace it.
When relocating your resistor to outside of the fan assembly, it would also be worth relocating the relay. One of the main causes of the relay sticking is the horizontal mounting of it. These relays are not really designed to be mounted horizontally. The heat inside the relay affects the return spring on the armature and often prevents the contacts opening. When mounted vertically, gravity assists the opening and you have less problems. This failure mode is also often seen in driving light relays (pre-LED more so due to the load).
Remove the old relay & holder from the fan assembly, it can be now mounted vertically to the ground stud below the engine mount. Cut out the old 2 pin plug out & connect directly to the relay base wiring (my connector was damaged anyway, so it saved me having to replace it). Use the high speed wiring to the fan (connected straight through at the old relay housing) to feed both full speed & low speed to the fan motor. It will now be much more reliable & easily accessed in the future. Mine has been running for a couple of months now without any re-occurrence on run-on with the original relay.
It will require some wiring mods before the fan connector at the top of the radiator, but it will now be compatible with the later model single plug fans, and not require any mods if the fan is replaced in the future.

 

fixed mine yesterday. pretty straight forward with the great info on here. I am a former aviation electrician (and a journeyman at that) so wiring was quite easy. Soldered mine because that is most secure and went with the no cut version and just ran both wires in parallel to my resistor. Piece of cake!

 

I don't think that will pass general aviation air worthiness inspection.

 

Oh, you'd be surprised what will pass...lol. It is quite secure, thread locked with stainless screws and the required Thermal Paste.

 

No kidding. Like the 737 Max.

Soldering workmanship spec. There ought to be a GA equivalent of this.