A few days ago I decided to service my supercharger. Upon putting it back together and letting the car warm up and driving it about half a mile, it started to dump coolant down the center of the block. I let It cool down and drove it home and found out that it only leaked when it was under pressure. So I removed everything and switched back to the old o-ring on the water pump inlet. This time when everything was together it was leaking from a different spot, the hose that connects the water pump to the radiator, leaking from the end that goes onto the water pump. I decided to switch the stock hose clamp to a worm-style one and the leak was fixed. After about 5-10 minutes of letting the car idle with no leaks, I noticed a ton of steam coming off the radiator and saw that the fan was not spinning. I'm pretty sure that the fan was working before I changed the o-ring and hose clamp but not completely sure.

I've checked the fuses and relays in the engine compartment and they all seemed fine. The fan only comes on when the A/C is on. I've put the car into 7.0 test and the temps got up to 90 before they cooled down to 85. Then I put the car into 7.1 test and temps showed 280, I guessed that wasn't Celsius so I converted and it was 137C. I read somewhere that the fan should come on at 106C, but mine never turned on.

It also started to rain pretty badly when I was taking the car apart for the 2nd time and the last part I got into the garage was the radiator with the fan attached. Could something have gotten rain damage? I also completely covered the engine with a tarp and plugged any holes so that any water did not get into unwanted places.

I was thinking that since this car has 233k miles it might be the resistor in the fan that might be bad, as I know they go bad easily.

What should I check next before buying parts?

 

Before buying a new radiator fan, you can test if low-speed fan works by unplugging it and putting 12V directly on it.
You didn't say what model year your car is. I'm pretty sure pre-facelift and facelift cars have a different fan connector, so which pins you need to put 12V on is going to be slightly different.

If you can confirm high-speed fan works and low-speed fan doesn't when putting 12V on it, you need to either change the resistor or the whole fan assembly (on my pre-facelift R50 I opted for a whole fan assembly change)

Indeed, low-speed fan should come on at 105°C, and high-speed fan at 112°C.

 

My car's year is 2003. Should I just use pieces of wire? 1 for ground and then one for 12v?

Also, the fan comes on whenever I have my A/C on. Does that mean the low-speed fan works?

 

Pre-facelift then, I can advise you since I did those diagnostics on my car.

If possible, use an external 12V power supply that's less powerful than your car battery. If you mess up with the wires and short the battery .... Well bad things can happen because of the high rated current of those, don't say I didn't warn you.

Anyway, pre-facelift, you have 2 fan connectors. They are at the right of the radiator, right by a AC fill line.
The big one has 3 wires, the small one has 2 wires.

To test the high speed fan, unplug the small connector (leave the big one connected) and put 12V between the 2 pins. Which side you put power/ground on does not matter. It will activate the relay in the fan assembly, and the high speed fan should turn on. If it doesn't, either the relay in the fan assembly or the fan is dead.

To test the low speed fan, unplug the big connector (it doesn't matter if the small is connected or not) and put 12V between the black wire (ground) and the smallest of the red/blue wire (12V). The low-speed fan should turn on. If it doesn't and high-speed fan does, the resistor is toast.

For reference, here's the diagram. It's a bit confusing because "second stage cooling fan switch" is part of the fan assembly with "engine cooling fan", but you can see the top 2 wires going in the switch are the small connector, and the 2 red/blue along with the black one are the big connector. You can also see the low-speed fan resistor that's somehow in the switch on the diagram, even though it's a separate component in the fan assembly.

 

There is also a simple work around fix: without having to replace the entire fan assembly or take apart your original fan assmbly in order to replace just the burnt out low speed fan resistor with the same (sure to fail) or aftermarket.
It simply requires by passing the burnt out resistor and wiring in a replacement external aluminum 100W 0.33 OHM 5% resistor.



The Link to the original post can be found here on NAM: "Low Speed Fan Resistor - we need solution"
Note*** The resistor described and used in the discussion will get extremely hot (300° +) while the low speed is activated. Be sure to use thermal paste between the resistor and metal mounting surface.***

I preformed this simple permanent low speed fan resistor fix on my own Mini 3years ago and am confident it will never fail again.
Even if the entire fan itself mechanically fails all together.

Note: This is not meant as a recommendation -
I opted to mount my resistor in a different location than described in the linked discussion. It is mounted/secured with 2wo small strips of 3M high bond double sided tape, flanked and elevated off the surface 3/32" to allow cool air to pass under and around the resistor.
It was just my preference and has never caused (melted) any problems for me in the past 3 years.

Follow the directions outlined in the link I posted.

 

Oooops - my bad.
The above fix is for a single plug connector and not for the early 2wo (large & small) connection consistent with the early model Mini.

But I hope it may help someone else.

 

Figured out why my fan was not working. The wiring came undone on the resistor.

The fan now works after fixing the wires!