Porsche Enthusiasts Club Forum

Hi Guys,

Well I thought I had solved my electrical woes with a rebuilt alternator but it appears not. Basically when driving the car, I will hear a whine start in the car( can be after some acceleration or cornering, or even bumps, the voltage on the dash goes above 14 and flashing the lights pressing the windows up will give a massive drop on the gauge, the stereo will lose power and eventually the abs light and handbrake light come on. It points to a bad earth somewhere, but I'm buggered if I can find it. I've checked and cleaned all the main earth points, some were corroded. I've pulled the stereo out and taped any loose wires. The strange thing is its intermittent, I can do a trip and it wont happen, on the next trip it will be all the time. Turning the engine off can clear it as well. The cruise control sometimes wont work as well, this links to 15 amp fuse that also does the abs and brake lights. I'm wondering if I have an earth issue with the abs sensors. I found a post on pelican forums that stated this

"I suspected it is a bad connectivity given the voltage spike. I cleaned all the ground straps on the abs sensors. there are two under the hood and 4 under the rear of the car.

each were cleaned with sand paper and contact cleaner. it turned out the rears were bad. "

Thing is I cant find any reference to where these are.

What I do know is that on my drivers side at the front there isn't an earth lead coming out of the barrel connector to the strut, but this has been like it for ages so I'm thinking maybe its not that. Are the barrel connectors available ?

Help !

Hmm, strange symptoms indeed. I would be having a good look at the battery terminals here, as it could be that due to a bad connection, the battery is actually going out-of-circuit. This would give rise to a high voltage reading, as the alternator would not be feeding the battery load, and has lost the smoothing that the battery gives the system. I had a weird problem similar to yours, I traced it to a bad battery earth strap. It all looked good, but when I wiggled the strap where it goes into the lead terminal connector, a very high resistance reading would be seen across this lead. It should be practically a short circuit. I assume that the connection inside the lead connector had broken down and was probably corroded. I replaced the lead and everything has been fine since. Worth a try??? Of course, also check the +ve connections too!

I assume I can get one of these from Euros ? Just a standard battery earth lead ?

Something like this ? http://www.ebay.co.uk/itm/CLASSIC-CAR-E ... 0707672146

How do you mean +Ve connections...I'm a bit of a dunce with electrics....

Ok, the lead you show would not be suitable. Have a look at the leads you currently have on your car, there will be one that goes from the battery negative pole (-ve) down to the chassis ground point. It will have a battery connector on one end and a bolt-through connector at the other. The terminology I used +ve signifies the battery positive. I thought is best that you check both, as one or the other could cause the problem. I wouldn't recommend just going out and buying another lead, as it may not solve the problem, best to get under the bonnet (or in the boot!), and have a good visual and tightness check of both battery leads and terminals. Something may be simply loose, there may be corrosion on the terminals, and so on...hope that helps.

Both connections are tight. I've cleaned the connections on the earth where it goes to the chassis, I hit that early on.

http://www.ebay.co.uk/itm/12-30Cm-Kit-C ... SwCU1YojU6

That looks more suitable as it has the battery clamp.

Hmmm, its driving me mad.

It's rare, but it is possible for there to be a bad connection internally in the battery... have you tried a different battery? As Rhett says, the symptoms sound exactly like the battery becoming disconnected from the circuit, and it sounds like you've checked everything around the battery!

Well I went down the local motor factor on Saturday morning and got myself a new earth strap. I've done about 80 miles so far and its all been good, so fingers crossed its sorted.

May well be that, maybe not and it's coincidence. I had exactly this after securing a rebuilt alternator from "the alternator man". It was the alternator spiking. Changed the alt again and all good.

My money would be on your rebuilt alt being defective.

Stuart

It was the same issue before the alternator was rebuilt. This is the same place that rebuilt my Dads one as well, which has been fine. Usually my issue would show up at least once on every journey, more so when the lights were on. I did notice last week that after re-tightening the battery clamps and wiggling the earth strap about that it was a lot better.

I will keep an eye out though....

Ok, good luck. My problems only started with the new alt. Seems you may have a different issue!! Weird that all the symptoms were similar. I couldn't make sense of voltage increases with poor connections or straps, still can't, surely you would lose voltage through poor connections and big resistances, but good luck anyway!

Edit to add when mine spiked, which could be reset by restarting, my voltage went up off the scale, it did not drop when called upon. Suddenly my dash lights were very bright, my electric windows went at warp speed and my headlights could see to the moon!! Then my ABS light sometimes triggered and the radio went on and off, clearly this was due to 15/16v going through everything!!

Stuart

Thanks

Mine pre-alt rebuiltd would show between ~12.5 on the scale, then a flash of the lights for example would cause a massive drop on the scale and the stereo would reset/ abs pump would cycle.

With the rebuilt alt, the scale would show just under 14, then when I would hear an electrical whine the scale would spike just above 14 and pressing the windows up ( when they were already closed) would cause it to reset itself and then show the ! light and abs light. Everything pointed to an earth...I cleaned loads of them everywhere, after the battery was suggested and I had a fiddle with the earth lead it helped.

Fingers crossed, now I just need to sort my drivers wiper out as it keeps popping out of the ball socket !

Good progress then. I was getting about 13.8v across the battery and had no issues (with fixed alt that is) but was noticing quite big drops sometimes when using electrics. I cleaned the battery strap and main bulkhead earths, as well as battery terminals, and applied de-oxit and now get 14.1v across the battery, at idle, and drops with electrics on are a bit less. Basically you'll have high resistance in a lot of places with 30 year old cables and connectors, which is what is causing the biggish drops when you switch stuff on. I plan to do the starter terminals next as well as getting to all the other earth points. It wouldn't do any harm to replace the main cable from battery to starter either but I seem good for the time being.

Stuart

Good tips there Stuart we seem to be getting plenty of posts concerning electrical problems. It's probably a time scale thing. 20+yrs in this damp, cold, salt infested climate is taking it's toll. We have done better than some old French and Italian cars and bikes (I've had 2 Ducatis). Worst ever was a Chrysler Sunbeam Horizon you never knew what would fail next