Alternator Fault?

[arwel 43 2 Cars]

Evening people. I replaced the alternator on my Mi16 powered rally car about 2 months ago now. Since fitting it I've noticed that it doesn't seem to start charging the battery untill the revs reach 3000rpm. Its a brand new alternator, not sure on which brand but its a 100 amp unit. Could this be an alternator fault or more down to the wiring not being upto the job any more?

Cheers

Arwel

[Ryan 99]

Is the battery warning light connected?

 

It doubles as a load on the alternator to help it start charging at low revs.

[arwel 43 2 Cars]

That is a good point. It should be but I'm pretty sure that we when the alternator wire broke and shorted out the old one.

I'll check it out.

[bondo 6]

If it only charges once you have reached 3000 rpm then the alternator is 'self-exciting'. Means the little lead to it isn't connected or broken for sure. Until you sort it just blip the throttle to 3000+ and it will continue to produce charge until you kill the engine - it only needs to be at 3000+ once in any running cycle to start the alternator charging.

[arwel 43 2 Cars]

If it only charges once you have reached 3000 rpm then the alternator is 'self-exciting'. Means the little lead to it isn't connected or broken for sure. Until you sort it just blip the throttle to 3000+ and it will continue to produce charge until you kill the engine - it only needs to be at 3000+ once in any running cycle to start the alternator charging.

Thats exactly what I've been doing.There must be a break in the wire somewhere then so I shall replace that and hopefully problem will be solved.

[jackherer 543]

Does the battery light come on when you turn the ignition on? If it hasn't come on at all for a while it might just be a blown bulb, the wiring could be fine but without the bulb the alternator wont excite.

[arwel 43 2 Cars]

Does the battery light come on when you turn the ignition on? If it hasn't come on at all for a while it might just be a blown bulb, the wiring could be fine but without the bulb the alternator wont excite.

I'll have to check that as im not entirley sure. If the bulb has gone is it just a case of putting a new one in and that will solve the problem providing the wiring is fine?

[jackherer 543]

Yes, the bulb is the only thing the small wire from the alternator is connected to so if it is blown it is the same as the wire being disconnected.

[arwel 43 2 Cars]

Thanks very much for that, I'll check it out tomorrow.

[jackherer 543]

I just found this diagram, it's not for a 205 but it is close enough:

 

 

edit: You can also test the bulb and wire by unplugging it from the alternator and grounding it to e.g. the engine block with the ignition on but engine not running.

Edited November 21, 2014 by jackherer

[dobboy 231 2 Cars]

Evening people. I replaced the alternator on my Mi16 powered rally car about 2 months ago now. Since fitting it I've noticed that it doesn't seem to start charging the battery untill the revs reach 3000rpm. Its a brand new alternator, not sure on which brand but its a 100 amp unit. Could this be an alternator fault or more down to the wiring not being upto the job any more?

Cheers

Arwel

 

 

Arwel, unless you've upgraded the mains from the Alternator your probably very near or above it limits at 100A

 

Why did you need a better Alt?

 

Just a thought but could the belt wheel fitted be incorrect for your set up?

[arwel 43 2 Cars]

All wiring has been updated when we moved the batter to the boot.

Bigger alterntor was bought to better suit the mi16 motor and to help cope with the electric pulls on nights events with the big spots etc...

 

The light doesn't light up on ignition so guess that's the problem anyway.

[jackherer 543]

That's definitely the problem then, now you just need to find out if it's the bulb or wiring. Did you try grounding the wire to see if that lights the bulb?

[arwel 43 2 Cars]

That's definitely the problem then, now you just need to find out if it's the bulb or wiring. Did you try grounding the wire to see if that lights the bulb?

 

Not had a chance to test anything yet. This weekend now I'll carry out my investigations.