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The mkiv Supra Owners Club

Alternator... again!!


kitch79
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Morning guys. At the weekend my (looked like new) refurbed alternator crapped it self, after approx 2.5 years. I was 50 mile from home on lvl 10 of a multi story car park!! Urgh.

I had a hangover and wanted to just get home, so bought a battery, swapped it, and it got me home. Although I’ve either buggered the new one or it was fubar when I got it. As... 1 mile from home I could smell eggs, opened bonnet and the new battery was smoking, and had leaked a little acid!!

So 2 things.

1 :- Could a non charging/working alt do this?

 

2 :- can anyone recommend a new alternator before I spend near 300 quid on an SRD One. Want to stay away of refurbed now.

 

Thanks. Supraless, driving mothers aygo, Kitch. [emoji30]

 

 

 

 

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for the battery to be smoking and bubbling i'd say that overcharging. Perhaps the regulator has died on the alternator.

 

Either way you'd be probably wanting to fit a new alternator from Keron or SRD one along with a new battery.

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I haven't come across boiling batteries for over 30 years. If you are pushing more than 14.5V out of the alternator its regulator is fubar and that will cause the battery to overheat and perform electrolysis of water to its constituent gasses. A working regulator will kick in normally at 14.2V so check what voltage is reaching your battery with the engine running at fast idle and that'll tell you how bad the regulation is.

 

Its probably about right though, Japanese or German alternator 20 years, Chinese 2 years.

Edited by rider (see edit history)
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Cheers guys. I’ll take a look at TCB and give Keron a shout.

I’m waiting on some bits then I’ll test my old battery with the buggered alternator.

The over charging thing does sound right, but the old battery which I replaced with the boiled new one, was totally flat!! Wouldn’t even unlock the doors the morning after I realised the alt was gone! So surely if the alternator was Over charging it, it would have had charge and broke that one too?

I’ll find out either way. Then proceed to buy a new alt, and see the my old bat is like.

 

 

 

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Cheers guys. I’ll take a look at TCB and give Keron a shout.

I’m waiting on some bits then I’ll test my old battery with the buggered alternator.

The over charging thing does sound right, but the old battery which I replaced with the boiled new one, was totally flat!! Wouldn’t even unlock the doors the morning after I realised the alt was gone! So surely if the alternator was Over charging it, it would have had charge and broke that one too?

I’ll find out either way. Then proceed to buy a new alt, and see the my old bat is like.

 

 

/QUOTE]

 

 

 

 

 

Sent from my iPad using Tapatalk

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Cheers guys. I’ll take a look at TCB and give Keron a shout.

I’m waiting on some bits then I’ll test my old battery with the buggered alternator.

The over charging thing does sound right, but the old battery which I replaced with the boiled new one, was totally flat!! Wouldn’t even unlock the doors the morning after I realised the alt was gone! So surely if the alternator was Over charging it, it would have had charge and broke that one too?

I’ll find out either way. Then proceed to buy a new alt, and see the my old bat is like.

 

 

/QUOTE]

 

Hi

Over charging will have killed the battery

 

 

Sent from my iPad using Tapatalk

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Its worth checking the S wire (sense) -this connects to the battery via the ALT S fuse and provides the alternator with the voltage of the battery , hence -sense , if this wire or the fuse has a high resistance , loose or rusty fuse connection for example , the voltage sensed is low ,so the alternator pushes up the output voltage to correct the low voltage - this can boil the battery due overcharging .

these are old cars with old wiring and often messed about with ....

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Well, after getting what I’ve been waiting to turn up, I tested the fully charged old battery. 12.8v after it was fully charged few days ago. So shot in the car, connected it up and started the car, checked voltage .... 18.83v!!! So I can 100% say, it’s overcharging and it’s what made the new battery overheat and smoke. Balls.

The old one only ran on the car for 10 min last Saturday so I’m quietly confident it will be ok. The new one however. Prob skip material.

I’ll have a search around for s wire and alt fuse when the weather ain’t so shit jagman.

 

So for now, it’ll stay sat till I either buy a new alt, or find an issue I can resolve.

 

Cheers guys.

 

 

 

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  • 11 months later...

Rebuilding is the cheaper option, diode pack, regulator and brushes are all that's needed normally unless you are really unlucky and the windings are cooked. Easily within the capabilities of most people to be honest, though I struggled to find an exact match for the diode pack used on the TT and ended up buying a diode pack for something else (v8 soaraI think) and modifying the main copper connector stud but 2 years on and still working fine. Nice thread resurrection:)

Edited by Shane
typo (see edit history)
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