Need some help with electrical issues.

I am on my second battery in 3 weeks. I’ve had the car for a couple of months and it’s had some idle / stalling issues. So far I had the LH rebuild (still have idle / rough driving) so issue for this may be somewhere else (ICV or MAF maybe).

Anyway, this aside I had a new battery installed a couple of weeks ago. Started the car fine today and went for a drive of about 3 miles. Got home and turned the car off. As I tried to lock the car the central locking / alarm was not working due to the battery being absolutely dead…. Second time in 3 weeks. The only electrical system I recall using was the fan while the car was running. I suspect the battery is fried due to over charging.

I am fairly useless when it comes to electrics so no idea where to start looking. When the battery was replaced the guy did a quick check with the new battery installed and said the alternator charge is fine. Can anyone share some thoughts on what may cause this or recommend a good auto electrician in the London area that knows their way around a 928?

I have done only 2 runs with the new battery of about 10 miles in total so doubt this issue is due to a drain as the battery was dead after the drive...

 

When you say absolutely dead, do you mean when you measured the battery's voltage it was zeroed ?
or
Do you mean when you got back from your drive nothing electrical worked ?

Rear ground strap comes to mind as a culprit.
Any work under the car recently ? Perhaps battery output line non-unioned with the starter.
And, check the battery's voltage with a voltimeter. Check at the battery and then check at the jump post. Would be interesting to see the results.

 

With dead I mean when I switched the car off and tried to lock it with the remote nothing happened so I used the key and only the drivers door locked.... exactly as with the previous "new" battery. There was no power at all from the battery and nothing electrical worked.

So I got back into the car to try and start it and absolutely zero electrical power. Not a single light coming illuminating on the dash.

These are the same symptoms as a couple of weeks ago. I had the AA out to replace the battery and when they checked it they said the battery was defective. As they had to replace this battery free of charge after just a week the guy checked the battery (12.3V and 720 amp). He also checked the alternator charging when the car was running and all tested fine.

As mentioned I only wen for a drive around the block.... got home and when I switched the car off everything was just... well.... dead.

 

You proved you have no functional electrical power, but you have not proved you have a 'dead' battery. You may have an (open) 'dead' power circuit.
You need to get to a 928 guy by you.
Hopefully a bloke will chime in.

 

You have had the car a couple months w/o batt issue, so something recent happened. One of the first tools you should buy is a DVM and batt maintainer, (Schumacher or one that does <1.5 amp, then just keeps you up to speed - jump packs can send a spike and damage the computer, I wouldn't use one) so you can get a reading on the batt; a load test is better, b/c a weak cell can show 12.5, but still be bad, this doesn't seem to be your issue. Search is your friend -- almost all of these cars have batt drain to some degree. Old ground strap is frequent cause, not of a drain mind you, but of an issue. They can look fine and be corroded w/i which amounts to a bad connection; all electrical grounds need to be cleaned in time. It sounds like your alternator is not alternating, but the batt connections are the place to start.

 

that drive you just took may have been on battery juice only....alternator may not be charging...however "if" all wiring is in order i.e (not butchered by PO) at least the alternator "red" light at the instrument cluster's volt meter "shouild " stay on while driving
charge battery start looking for clues
best

 

Could still be as simple as ground strap.

Actual voltage reading of battery is first step.

 

Also, what year is your car ?

 

Thanks for all the responses. Fingers crossed the issue is resolved.... As simple as a corroded ground. The car has a cut out switch for the battery and the earth on this was corroded so the alternator charge did not get back to the battery. Cleaned up the corrosion and the charge got back to the battery. Also, the (-) terminal was corroded as well and lost another 1V there, so got the terminal shortened a bit and put a new battery connection on. I was out for a few short drives and no issues.

The big plus is that this appears to have solved various other issues! I had poor idle / revs surging so got the LH rebuild by JPS. Still had idle issues after so thought is was the ICV and sprayed carb cleaner down the pipe leading the ICV - poor idle remained. Also on odd occasions got random fault messages on the dash. These issues have all now gone away.... I am not quite celebrating yet but so far so good.

 

Good news! I'm guessing it's fixed. Poor grounds can cause a lot of problems.

 

gamut 200,
I really am glad for you. I had a feeling it was a ground (earth) issue. You have lots of ground on this car , and they all need to be tip-top or you will have problems.

 

When asking for help, you will get faster and better answers by including the car info - model year, USA/RoW, auto/five speed, etc.

 

Given what you say - I'd change the ground strap anyway. if you had corrosion elsewhere - it is also likely to be toast too...

Alan

 

+928

When Alan and Wally chime in-you listen.

You need to check all grounds. You also need to figure out why the PO put in a cutoff switch--usually they have an aftermarket alarm and/or radio or some doohickey attached. Cutoff switches are great for the track but I'm no fan for daily drivers-especially since many are not up to the amperage requirements and also they are usually a patch for the symptom rather than the cause.

 

When it comes to the 928,
this is as true as death and taxes.