R50 MINI Cooper (2002-06) R53 MINI Cooper S (2002-06) R52 MINI Cooper Convertible (2005-08) R52 MINI Cooper S Convertible (2005-08)
New alternator, new brushes, new alternator belt
Replace the brushes and check the electrical grounds before you replace the alternator
Consistent charging output
Replace drive belts
This article is one in a series that have been released in conjunction with Pelican Parts' new book, How to Maintain and Modify your new MINI. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 500+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any MINI owner's collection. The book is due to be released in late 2012. See The Official Book Website for more details.
Check out some other sample projects from the book:
The alternator provides your car with a constant source of electricity while the engine is running. Over time, the alternator can begin to fail and start causing trouble with the various electrical systems in the car. If you suspect alternator trouble, you need to check to see that is operating correctly, and is indeed the cause of the problems with your charging system. Sometimes bizarre electrical problems can be caused by a number of faults other than the alternator. It’s important to troubleshoot the system prior to replacing your alternator.
The first thing to check is the belt that drives the alternator. Is it tight and amply turning the fan? If not, then check that the belt tensioner is working correctly. Modern belts seldom break, but they get brittle and glazed with age, and can slip on their pulleys. Replace the belt with a new one.
The next item to check is the voltage at the battery. This should read a little more than 12 volts with the engine off. When the car is running, the voltage should read at in the range of 13 to 14.5 volts with the engine at 2000 rpm. If your battery appears to be leaking, then your voltage regulator has probably failed. The battery will usually only leak acid if it has been overcharged at a much higher voltage. If the voltage measured at the battery is more than 16 or 17 volts when the engine is running, then the regulator is probably bad. If your battery has boiled over and has acid overflowing out the top, make sure that you clean up any spilled acid immediately. Dousing the area with a water and baking soda solution should help considerably to neutralize the acid, and prevent it from eating away at the metal.
An important item to check on your car is the engine ground strap. The engine is electrically isolated from the chassis by rubber motor mounts. If the engine ground strap is missing or disconnected, then you might have a whole bunch of problems, including electrical system malfunctions and difficultly turning over the starter. The ground strap is located just in front of the passenger side engine mount.
If you’ve checked all of these things and you still have charging problems, it’s likely the alternator will need to be replaced. In order to remove the alternator, you’ll need to extend the front bumper into the service position or remove radiator and hoses completely. It is possible to replace the alternator without removing radiator. See our articles on replacing these for more detailed info.
Before starting any work, make sure that you disconnect the battery. The positive battery terminal is directly connected to the alternator, and it can be dangerous to work on if it’s live. Next, remove the front bumper and carrier, along with the radiator and hoses.
Now remove the belt that drives the alternator (See Figure 1 and Figure 2). Refer to our project on replacing the serpentine belt for detailed instructions on the belt removal.
On the back of the alternator, you will see two electrical connections, one is a plug style connector and the other is a ring style connection. Press the tab on the plug style connection and pull the plug out of the back of the alternator. Now remove the 10mm nut holding the 12v lead wire to the back of the alternator and remove the wire (See Figures 3, 4 and 5).
Next, remove the three 13mm bolts securing the alternator to the engine. You’ll see that the upper bolt doubles as a mounting bolt for the supercharger. Once the bolts are removed, carefully remove the alternator from the engine block. (See Figure 6 and Figure 7 ).
Now, a quick word on replacement alternators: Sometimes new or rebuilt alternators are supplied without the drive pulley attached: you need to transfer them over from your old unit. Removal of the pulley can be tricky if you don’t have an impact wrench (a good reason to buy an electric one). Also useful may be a strap wrench, which is a handle with a rubber strap on it that can secure and tighten around a pulley. Take notes as you disassemble the alternator pulley assembly: it must be assembled in exactly the same manner on the new rebuilt alternator.
Now take the new alternator and mount it back up to the engine. Torque the mounting bolts to 25Nm (18 ft/lbs.). Reattach the electrical connections on the back of the alternator and you’re all set. All that’s left is to install the serpentine belt, radiator and hoses and finally the front bumper and carrier.
(R50 Cooper): The R50 non-supercharged cars have a slightly different mounting of the alternator. You don’t need to remove the radiator to remove the alternator; however it does make replacement a lot easier. For our purposes, the radiator panel has been removed to make the procedure a bit clearer. If you choose not to remove the radiator, you will need to put the car into the radiator service position. Please refer to our article on radiator service position for more info.
Remove the front splash shield under the front of the engine. Then remove the front right wheel and also the right wheel housing liner. Once removed, take note of the serpentine belt routing and remove the serpentine belt. Please refer to our article on Serpentine belt removal specific to the non-supercharged cars.
Once the belt is removed, locate the electrical connections to the alternator along the front of the engine. It’s a bit of a tight fit, but you should be able to access both the electrical plug and also the 10mm nut holding the 12v lead to the alternator.
With the connections removed, locate the three 13mm bolts holding the alternator to the engine block. Two are located on the bottom flange of the alternator and one on the top. Some cars have a small spacer bushing on the back of the top bolt between the alternator and the block. Remove the three bolts and carefully remove the alternator from the engine compartment.
Now place the new alternator up against the block and thread the two lower bolts in. On some cars, you may need to re-use the spacer bushing on the back off the top bolt. Test fit the alternator to see if you need it. If there is a gap in between the alternator and the block with the two lower bolts threaded in, re-use the spacer.
Now re-fit the 12v lead wire to the ring terminal on the new alternator and torque the bolt to 10Nm (7ft/lbs.) Plug the electrical connection into the new alternator and re-fit the serpentine belt. Release the belt tensioner and re-install the wheel housing liner and also the wheel. Now re-fit the front splash shield to the front of the car.
(R55/R56/R57 Cooper and Cooper S): On R55/R56/R57 cars, removal of the alternator uses a different procedure then the early cars. You’ll need to extend the radiator support into the service position (See our article on R55/R56/R57 Radiator Service Position) and also remove the serpentine belt (See our article on Serpentine Belt Removal). Now remove the belt tensioner from the front of the engine. This is held in place with two Torx bolts. These bolts also hold the top of the alternator to the engine block.
Next, remove the electrical connector and also the 13mm nut holding the positive cable going to the alternator. Make sure that the battery is disconnected before touching the positive cable. Finally, remove the lower Torx bolt securing the alternator to the engine block and carefully lift the alternator out of the engine compartment.
NOTE: Depending on the year and options with each vehicle, there may be alternators with different amperage ratings. Depending on the alternator, there are different harnesses available to make each alternator work. Use your VIN number to determine which alternator is needed for your car.
Use the belt tensioner tool to release tension on the serpentine belt and lock the tensioner in place by inserting the factory pin or a small Allen wrench (purple arrow) into the second hole in the tensioner arm (green arrow).
(R50 Cooper): Now turn the alternator over so you can access the 13mm nut that holds the battery cable in place (green arrow) and also the electrical harness that plugs into the back of the alternator (purple arrow). Once these connections are removed, you can remove the old alternator from the engine bay.
(R55/R56/R57 Cooper and Cooper S): Shown here is the alternator in a R56 Mini Cooper. To remove the alternator you’ll first need to remove the serpentine belt (not shown) and then loosen and remove the two upper Torx bolts (green arrows) holding the belt tensioner to the engine. Remove the belt tensioner and then unplug the electrical connector going to the alternator (purple arrow). Next loosen and remove the 13mm nut holding the positive cable to the alternator (red arrow). Finally, loosen and remove the lower Torx bolt securing the alternator to the engine block (yellow arrow). Now carefully remove the alternator from the engine compartment.
Comments: Your Hot Tip section suggests replacing the brushes first. Where can I get info on that procedure?
March 4, 2014
Followup from the Pelican Staff: Remove the alternator, then remove the regulator from the alternator. There should be a few small bolts. First check if the regulator is available. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part. - Nick at Pelican Parts
Comments: In this article you refer to "radiator service position". Where can I find that article?
October 8, 2013
Followup from the Pelican Staff: Try the article located at this link:
Comments: I'm about to put new alternator for my cooper s 2005. Mission impossible.
September 9, 2013
Followup from the Pelican Staff: It's not that bad. Follow this tech article and let us know how it works out. - Nick at Pelican Parts
Comments: Where is the article located that explains how to remove the alternator without removing the radiator?
July 19, 2013
Followup from the Pelican Staff: You have to move the radiator out of the way to replace the alternator. - Nick at Pelican Parts
Comments: Im in the process of removing the alternator on an R50 2004 mini cooper. This article is much better than the Haynes manual. However I would stress you DO need to buy the mini belt tensioner tool. I had to remove the fuel tank vent valve mounting as well though otherwise the tool wouldn't travel quite far enough to be able to put the pin in.
Also in putting the radiator into service position you dont mention removal of the crush tubes.
Great articles though!!! You should publish these. And more. I would buy it.
April 2, 2013
Followup from the Pelican Staff: Thanks for the feedback. - Nick at Pelican Parts
Comments: I'm desparate for R50 2004 mini cooper model
October 24, 2012
Followup from the Pelican Staff: There are a quite a few out there. Check a local want ad. - Nick at Pelican Parts
Check out some other sample projects from the book:
Applies to: R50 MINI Cooper (2002-06) - R53 MINI Cooper S (2002-06) - R52 MINI Cooper Convertible (2005-08) - R52 MINI Cooper S Convertible (2005-08) - R52 MINI Cooper S Convertible (2005-08) - R56 MINI Cooper (2007-) - R57 MINI Cooper Convertible (2007-)