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Short Circuit

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circuit short
5K views 7 replies 4 participants last post by  Ryengoth 
#1 ·
Saab 9000 Aero, 1994, 2.3 Turbo

Parked car for 3 weeks while out of town. Everything had been working fine. Tried to start, battery almost completely dead, starter did not even click. Charged battery (it's relatively new) and it took full charge. Put battery back in car, as soon as i connected ground lead, huge arc and current draw. No blown fuses. Everything was basically turned off.

The car does not have a history of barmy draining when not being used..

Checked, could not see any evidence of rodent activity or damage. It would seem only the starter could draw this much current, but should not be engaging.

Any ideas? Have searched on-line and not found this particular problem

Thanks
 
#3 ·
Hi Neil,

Can I ask if you got to the bottom of your short circuit troubles?

I hadn't used my 9000 CSE for a week or so till I tried to last night but the battery did not have enough juice to unlock the doors.

The Duracell battery is less than 2 years old and it's on charge now.

Checking the car, I'm testing the resistance with a meter on the disconnected battery leads of about 1K ohms one way and about 600 ohms the other - so not enough draw there to flatten the battery I'd have thought - probably just the alarm.

Any thoughts anybody?

Thanks
Terry
 
#4 ·
Hi Folks,

Mine has gone and done it again. After my previous post, I'd been watching the voltage on the info display while using the car and its seemed fine but after leaving it for a few days, I've gone to use it and the battery was dead flat. I checked the voltage at the battery and it was less than 2v.

I had to go out instead of trying to localise the fault but by the time I'd returned, the short circuit must have cleared as the battery voltage had recovered to about 7v.

So I'm thinking that I have an intermittent short circuit on a high-current component like the starter, solenoid or alternator.

But on both occasions, the fault has appeared when the car has been at rest and there has not been enough juice to bring in the solenoid.

Has anybody any experience of anything similar?

Cheers
Terry
 
#5 ·
hughestt,

How old is your battery. Sounds like it is on its way out. The 2v was presumably just after trying to start the car and then after a short while the battery has recovered to 7v. Checking the voltage as you drive really only gives the alternator output. You should be getting about 14 v

Paul @ Kippen
 
#6 ·
Hi Paul,

The battery is less than 2 years old and there was not enough power to unlock the doors or light the dash panel, let alone try to start. I think the fault must have been present at the time the volts were down at 2v and then had cleared by the time I came back to check again. As there were no visible signs of a massive short circuit, I am working on the assumption that this was an alternator diode fault.

With this in mind, I fitted a refurbed (Unipart) alternator just over a week ago and so far, so good. I'm hoping for the best.

If the fault returns, then a new battery will be next.

Cheers
Terry
 
#7 ·
Hello Folks,

Well as mentioned, I had changed the alternator to try to clear the mysterious short circuit and all has been well for nearly two years but one day last week, I went to the car and saw that the battery was dead (<2v). Remembering my past troubles, I disconnected the alternator lead and the fault remained. Disconnecting the battery and measuring across the leads, I saw less than 1 ohm. My next step would have been to start pulling fuses but the fault then cleared.

My thinking now is that this must be an issue in the high current cabling from the battery to either the alternator or the solenoid/starter.

Does anybody have any similar experiences?

Cheers
Terry
 
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