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ALternator failure and large sparks! by Drfiero308
Started on: 12-22-2013 03:37 PM
Replies: 9 (203 views)
Last post by: Gall757 on 12-24-2013 10:12 PM
Drfiero308
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Report this Post12-22-2013 03:37 PM Click Here to See the Profile for Drfiero308Click Here to Email Drfiero308Send a Private Message to Drfiero308Edit/Delete MessageReply w/QuoteDirect Link to This Post
Hi everyone

If i had the alternator fail through failed diodes , would i see very large sparks when trying to connect a battery?
The narrative here suggests i would:
http://www.thefierofactory.com/qabatrundown.php
Thanks
Ian
V6 ferrari 308 replica fiero, battery was dead, now replaced but fusible link popped at c500 connection

[This message has been edited by Drfiero308 (edited 12-23-2013).]

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Blacktree
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Report this Post12-22-2013 04:04 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Are you trying to connect the battery while the engine is running? The alternator doesn't do anything when the engine is off.

Connecting the battery cables backward (while the engine is running) will also make lots of sparks.
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tebailey
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Report this Post12-22-2013 07:32 PM Click Here to See the Profile for tebaileyClick Here to Email tebaileySend a Private Message to tebaileyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Failed diodes will give you a straight through shot to ground, lots-a-fireworks.
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Raydar
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Report this Post12-22-2013 07:59 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by tebailey:

Failed diodes will give you a straight through shot to ground, lots-a-fireworks.


True. Engine on or off. Makes no difference.
Also, a failed (shorted) diode will kill a battery.
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Drfiero308
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Report this Post12-23-2013 01:27 AM Click Here to See the Profile for Drfiero308Click Here to Email Drfiero308Send a Private Message to Drfiero308Edit/Delete MessageReply w/QuoteDirect Link to This Post
Ok thanks. i think,this will be my problem. Can i test for continuity at the battery alt connection and ground to confirm?
Ian
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James Bond 007
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Report this Post12-23-2013 10:27 AM Click Here to See the Profile for James Bond 007Send a Private Message to James Bond 007Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Drfiero308:
Hi everyone
If i had the alternator fail through failed diodes , would i see very large sparks when trying to connect a battery?
The narrative here suggests i would:
http://www.thefierofactory.com/qabatrundown.php
Thanks
Ian
V6 ferrari 308 replica fiero, battery was dead, now replaced but fusible link popped at c500 connection

You will most likely see a spark when ever connecting the battery cables,regardless if your haveing any problems.If you have a charge gauge on your dash,it would probubley be reading way low,or way high (over or under chargeing), another symptom would be static comeing over the radio speaker.
More detailed information on your problem would help. I asume your battery isnt charging and there could be other causes. Worn headlight motors can easily drain the battery (try disconnecting the single power wire to the right and left headlight motor). Battery acid,on your battery cables,can prevent the battery from charging. A stuck fan relay can drain the battery too (doesnt happen very often,but the relay can stick).

[This message has been edited by James Bond 007 (edited 12-23-2013).]

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Drfiero308
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Report this Post12-23-2013 10:56 AM Click Here to See the Profile for Drfiero308Click Here to Email Drfiero308Send a Private Message to Drfiero308Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for reply. I have another thread on forum detailing a broader set of issues but summary is as follows
"
I bought a nice fiero 308GTB replica last week. It had a dead battery but jump started fine. The battery clearly was dead as a new one was required and simply connected the new battery in parallel to allow me to drive the car home (which it did fine for about 250 miles). Cabin volt gauge indicated between 12 and 14 volts - needle periodically flickered between these two displayed values.
I changed the battery over the weekend - which is a bit of a fiddle given the poor access. Car fired up fine but volt gauge showed 10v or so and, when driving around clearly was falling gradually. A multimeter across the battery terminals indicated no charge being received from the alternator.
In a fiero, the positive battery point has a feed to a nearby connector block, from which the main red cable links to the alternator. There is a fusible link in this cabling.
I poked around this connector block area and noted that a PO had cut the fusible wiring in the alternator cabling and then crudely wound the wires together and covered it in tape for some reason. I thought my poking around might have disturbed this connection and that this would explain why i had no charge to the battery. I reconnected this with a short 27amp length of cable and then reattached the battery.
Immediately, there were lots of sparks and the newly installed spliced cable simply melted.
Clearly I had a short that was earthing the battery directly through this cabling.

Reading around the topic as I can tell, then I could have failed diodes in the alternator allowing a direct connection to earth?
But just a bit confused as to why this happened now when before the battery install, even with the dodgy connection i found, the car was charging and running reasonably OK? Just a coincidence of problems?

Car is a 1987 Fiero V6 with aftermarket 308GTB body fitted.
The dash alternator light had never come on at any time"
Thanks
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Phil
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Report this Post12-23-2013 01:27 PM Click Here to See the Profile for PhilClick Here to Email PhilSend a Private Message to PhilEdit/Delete MessageReply w/QuoteDirect Link to This Post
The dash light bulb should come on when you turn on the key but not starting the car- a blown out bulb will stop the alt from charging.
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Drfiero308
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Report this Post12-23-2013 02:21 PM Click Here to See the Profile for Drfiero308Click Here to Email Drfiero308Send a Private Message to Drfiero308Edit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks- i have read that, but the battery was being charged before and the battery light had not come on....?

[This message has been edited by Drfiero308 (edited 12-23-2013).]

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Gall757
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Report this Post12-24-2013 10:12 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
That is a sensing circuit for the regulator in the alternator, so if there is any resistance, the circuit will do it's job. In theory, you could put the wrong bulb in, or the filament could break in a way that completes the circuit, and it would still work, but the light would be off. It looks as though your luck has run out, though, and the circuit is now open.
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