I have recently changed the alternator after it died in my diesel Yaris. I have done about 150 miles with the new alternator however it still doesn't start very well. It now takes 1 long or sometimes 2 starts and the engine sounds like its choking. The check engine light (CEL) is also on.

Do I need to manually charge the battery, change the battery or something more sinister? I need to do a long journey at the end of the week.

  • Who did the alternator change? If it's a garage take it back to them, they should stand by their work.
    – GdD
    Commented Jun 28, 2016 at 12:31
  • 1
    You say it 'still doesn't start very well', has the fault been present since before changing the alternator? If so I'd be looking towards glow plugs or the glow plug relay. They preheat the air-fuel mix before starting, without this the engine will be harder to start and initially run roughly once it's started.
    – tallpaul
    Commented Jun 28, 2016 at 16:58
  • I bought a new alternator because my mechanic couldn't be bothered to find me a cheap one but happily gave me a part number. He changed it. Unfortunately he is on holiday until next week. I will take it back. Based on what I read it could be the glow plugs. Could a fuse have gone because of electric fluctuation? Fuses are cheaper :( Commented Jul 4, 2016 at 18:20
  • It could be the glow plug fuse. Check that first. There is probably a relay for the glow plug control as well. Check that it is working too. Does the car smooth out after it has been running for a bit? In warm weather the glow plugs won't contribute much, so if it is warm where you are it could well be something else. If you know another diesel Yaris owner you might ask them to start their car without using the glow plugs to see if you notice a difference.
    – dlu
    Commented Jul 20, 2016 at 3:04
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    I'd say the first thing to do is to see if you can get the codes read so that you can find out what the CEL is about.
    – dlu
    Commented Jul 24, 2016 at 19:26

1 Answer 1


You will need to have your battery load tested. Autozone or similar performs this service at no charge. Assuming that you have driven the vehicle for some length of time, the new alternator should have charged your battery sufficiently- or perhaps not- that is why it should be tested.

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