I have a 2007 Justa with a broken serpentine belt.

Last night I smelled a burning smell, but nothing else was wrong other than occasionally it would almost die when stopped at a light (but never died).

Today when leaving my coffee shop my battery warning light came on, and strange whirring/whistling sound started coming from the motor. I made it to work and popped the hood to test the alternator. With the motor off, I was a little over 12v on the battery (it's a new battery too), and with the motor on, it was 11.5v. So I knew the alternator wasn't working ... BUT... then I looked down in the engine bay and the serpentine belt was broken.

So... is there a way for me to tell if the belt broke, causing the alternator to stop and deliver no charge, OR...did the alternator die, and cause the belt to break?

Thanks for whatever you can provide.

 

Can you turn the alternator by hand or is it frozen solid? If the alternator turns freely, it's probably just the belt. Either way you're going to need a new belt.

 

The burning smell suggests the belt may have been slipping. It could be because the alternator seized up -- ammodave's question can you turn the alternator by hand certainly raises that possibility -- or an idler roller even a tensioner roller bearing may have failed. So you want to make sure all idler/tensioner roller bearings are good. And the tensioner applies the right tension. The slipping could be due to insufficient belt tension.

Check all the accessory drives for any bearing play. A water pump with a worn out bearing can let the pulley/sheave **** a bit and the belt -- especially a serpentine belt -- can have its life seriously shortened by this mis tracking. A sign this might have been going on is the old belt -- if you still have it -- can have a sharp edge and a dull edge. The dull edge is normal. The sharp edge is a sign the belt has been rubbing.

 

Thanks for everything! My cooper died on the way home last night as I suspected might happen (I was running on battery at that point) and I had it towed to my house. I'll check the alternator movement tonight!

Other info that may/may not be helpful:
September 2018 had the following done:

• New water pump
• New belt tensioner (friction wheel)
• New Ac compressor/condenser
• New serpentine belt

 

Could be premature failure of one of the above. Could be something original failed. My 996 Turbo developed a noisy idler roller bearing. Had all replaced along with the tensioner. I don't recall how many miles later, quite a few though, and the signs of a bad idler roller/tensioner roller bearing appeared and I had all replaced again. All within 150K miles. The idler roller/tensioner roller bearings in my Boxster were original at 317K miles. With both cars the serpentine belt got changed on schedule.

Lost a V-belt off my VW Golf TDi. Not sure why. Had it replaced on schedule. Never had any V-belt or serpentine belt problems with any of my cars. (The Turbo I mentioned that was not a belt problem but an idler roller bearing/tensioner roller bearing problem.)