Mod Details

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Get The Right Alternator

When I initially fitted a replacement alternator to my Roadster it didn’t actually work. I thought I had misdiagnosed the fault but actually I had been sold the wrong alternator for my car. On the smart there seems to be 6 different alternators but although they all fit, they won’t all work.

The big problem now is that Smart are no longer selling the alternator for the Roadster. People seem to having good luck with the following alternators.

Works (Apparently)

I haven’t personally tested any of these but…

Magneti Marelli MAN1009 (confirmed by S2Smarts)
Herth+Buss 32063341 (confirmed by Peter G)
Lucas LRA02000 (confirmed by Andy D)

May Work

Denso DAN521 (confirmed by Karl S M). This alternator used to work fine but apparently Denso started selling 2 types with the same number. 1 has a round rectifier and 1 has a square rectifier. The round rectifier apparently works and the square rectifier doesn’t. Check the bottom of the page for more details on this.

The AutoElectro AEC1734 (confirmed by Daniel G) all worked fine but now there are reports of some not working, so it looks like something has changed. Probably best to avoid.

What If I Ignore You?

From the number of emails I get from people who have ignored the primary rule, there is a very good chance you’ll be sold the wrong one for your car. For most car parts retailers, there is 1 alternator for every smart. So, if you do get the wrong one, you’ll waste time and money and you might even damage your car.

What Faults Can Occur?

It can be something simple like the battery not charging all the way through to the car not starting, the engine not running correctly, engine check light on, numerous stored fault codes, the car not revving, revs hunting and even the electrical destruction of the ECU. You may get a P2042 error code if you check with a generic error code reader.

How Do I Know The Alternator Isn’t Working?

With a cheap multimeter (that you really should own as it’s an essential piece of kit) you can test the alternator from the battery as seen on this page.

Method 1

This is an update to the existing page. The old method that was found here and on similar sites just wasn’t/aren’t well thought out. After having a little alternator crisis with my Roadster which resulted in having to remove and refit the alternator 3 times, I worked out a better way.

Jack the car up, remove the rear wheels, disconnect the battery and remove the arch liners on both sides. Remove the 3 plastic nuts with a 10mm hexagon socket and pull the arch liner out.

Protecting the belts is a plastic cover. Pull out the front plug…

Denso DAN521 Issues

The original version of the Denso DAN521 had a round rectifier which apparently worked correctly.

Then at some point, Denso changed to a square rectifier version which didn’t work.