Porsche Enthusiasts Club Forum

Well i have had my 1986 928s2 for two weeks now and today the 928 electrical gremlins decided to pay me a visit.

When the car was being driven some of the guages would fluctuate as though there was a bad earth, then they would settle down. The cd player would suddenly switch off, and when driving it home last night the voltmetre inside the car was showing just above 12v. This morning the battery is flat!

Whilst having the timing belt changed last week the garage put a new battery in the car as it was flat when they tried to start the car. The alternator was checked and showing 13.5 volts so it was deemed as serviceable.

I have driven about 100 miles since the new battery was installed with the car starting first time.

Is it possible all these problems could be down to one thing?

Any help welcome (dishartened 928 owner).

Martin.

Hi Martin,

First and simplest thing to check is the tightness and condition of the ground strap connection on hatch floor.

Does your car have any history of original wiring being disturbed - typically installation of aftermarket alarm or audio system?

The garage's diagnosis of alternator being ok may be flawed. But assuming they are correct I would start looking for unusually high current drains. Using a mutimeter you can check the drain at battery with everything turned off. Should be max of 100mA or so and normally much less. When doing this test you have to make sure all interior lights are off (don't forget door marker lights which illuminate when any door open).

If there is a high drain, then you need to work through fusebox to see which circuit is responsible. Maplin sells a gadget ("automotive current tester" or something like that which plugs in place of the fuse (original fuse inserts into the device) and reads current. Cheaper alternative (also Maplin) just makes it easy to insert multimeter in line with the fuse.

From your description of flickering gauges the problme may be intermittent, but try above ideasfirst.

Hi MartinAdrian'sns advice is spot on. To add a few comments, gauges fluctuating - especially the volt meter - are usually down to bad earth within the pod. Had this on my 1980 S1 and used to have to wiggle the pod/wheel adjustment up & down dramatically to re-establish a good earth then all would work well.

As Adrian has suggested, check all the ground points starting with the earth strap in the boot. Then look at anything that has been added as aftermarket, stereo's, amps, and the favourite - alarms! All these wcertainlyaily drain your electrics. Also the ashtray cigarette lighter connector is a favourite to "add" extra devices to & when selling a car these are typically just wire cut out so maybe check there are no stray wires left behind the cigar lighter plug connector pins.

Good Luck

Steve

Thanks for the advice.

Just to note that the alarm has been disconected some time ago, the interior lights work but not when the door is opend. An after market cd player has been fitted.

Also when the indicator is selected the volt needle moves in time with the tick.

What do you mean by the pod?

Excuse the ignorance......
Martin.

Martin, sorry I missed your text earlier. The pod is the part of the dash containing the dials etc. When you move the steering wheel adjustment, it moves the whole dash pod too. The earth strap in the boot is the place to start, as Adrian and Steve have said. I'm a bit busy this week, but might have time to look at club night on Wednesday night if the car can get there? I'd buy the wee gadget mentioned, from Maplins, and check each of the current draw from each of the fuses. Take care pulling the fuses. Maybe see if Mike Dowie can help you lookat it?

Well i put the battery on charge for about 2 hours then started the car and she fired up first time and the volt needle sat between 12and 14volts. I checked the battery with a volt meter and the battery was showing 13.5volts. Started her 30mins ago and again first time start!

The interior lights dont work when the door opens, but they were all work if you move the slider to constantly on, but now they dont work at all!

I have checked all the fuses and they are all good.

Next i will need to check the earth straps, but i think i may need an auto spark to go over the car.

Unfortunately i am working on the meet night Lee so you still wont be able to see my money pit!

Martin.

You may have corrosion at points where door pin switches are screwed into body.

Also one or more of your interior lights may have connections reversed from when someone changed bulb in past or replaced a light.