Originally Posted by abrescia

So... i started my 86.5 car last Friday night and ran it for about 5 minutes. No problems. The car sat in my heated garage until last night (5 days) and my wife started it and backed it out of the garage to sweep out the floor. Then when trying to start it again, complete deadness. No click, no buzzing, no warning lights or dash lights or interior lights. The clock works! I put a battery charger on the posts and at first it read 67% but it also read 12.3 volts. I left it on the charger overnight and this morning it read over 90%. Still complete silence when turning the key. ...

Originally Posted by Mrmerlin

OK what I thought was a simple instruction has been lost in space
Please read this slowly and carefully

it only involves adding 1 battery jumper cable to the car.

not adding an additional battery,
or car with battery,
or charging unit


without doing any battery terminal servicing
attach a battery jumper cable to the negative terminal of the battery( this will clamp over the existing ground terminal)

NOTE leave the car ground wire alone.

attach the other end of the grounding wire to one of the nuts for the rear shock.
This will add an additional ground circuit to your car and test you original ground wire and its connections.

See if the engine cranks and report what you find

Originally Posted by dr bob

!!!NOT THIS!!!



Re-read Stan's suggestion. Connect positive to positive, then negative to the donor car battery, other negative to the 928 TOP shock tower bolt or other solid chassis ground. NOT the shock piston rod and nut in he middle, use one of the three nuts.studs that pass through the tower metal just above and forward of the battery and spare wheel. Ultimately positive-to-positive, negative-to-negative, but keeps the last connection point clear of the potentially explosive gasses from the charging battery.


Going to the "last things worked on" list, start with the idea that Classic9 had the battery disconnected while they worked on the car. Clean and secure the clamps at the battery posts, plus the smaller positive feeder wires that attach to the positive post terminal. Then the ground strap and bolt where it secures to the rear bulkhead. If the ground strap is the original, add one of the upgraded ones to your next 928 parts order.

Next would be wiring connections related to the dash and console if they were out for work. Clean the grounds in the foot well on either side, as others have suggested. Those would not normally have been disturbed by the upholstery work but there's never any downside to cleaning 928 ground points.

The connector for the ignition switch deserves a look. A couple screws secure the harness connector to the back of the switch, accessible with an angled/ratcheting screwdriver and tiny hands. The contacts are self-wiping on that, so if you can slide it on and off a couple times then tighten the screws it removes a possible cause of your symptoms.

After that, the diagnosis will be more detailed, using a DMM to find open circuits in the ignition and starter wiring and connections.

My dime (you'll have to send postage to collect it....) sez you'll find the problem at the battery connections.


After all that, you'll want to do some electrical sleuthing to find the parasitic draw that's running the battery down. The target number is 35mA or so, same as 0.035 Amps; That's about 10% of what you are reporting for parastic drain. Something is stealing power. A typical 60AH battery will be completely drained in 180 hours or less at the numbers you report. It will drain to the point of not being able to crank the starter in a lot less than that. Good reason to find and fix whatever it is that's draining the battery. Know that each time the battery suffers a deep discharge, it loses about 20% or its remaining capacity. Half a dozen of those deep discharges cycles will turn a new battery into an old one.

I've kept a maintainer attached to the car whenever it's going to sit more than a few days between drives, a habit that started the first time the battery drained while I was on an overseas project for a month. The 928 mob counseled me, and from then the maintainer has been a constant 928 companion. I lift the ground strap if I know it will be a few weeks or more of non-use, just to save the battery the mini charge cycles. Parasitic drain on my S4 is around 30mA, with stock everything except the radio head unit.

Originally Posted by linderpat

Aaron - all of the above, but I am also still bothered by your description of when the problem began. I am wondering that if upon reinstall, something got crimped causing a small short/parasitic draw. Or, a ground was left loose in the pod. Could be lots of things that may be a PIA to chase down, but getting a volt meter might make sense at this point too, and working through the wires, or pulling the pod and inspecting the connections. Pod pulls are not hard to do.

Originally Posted by abrescia

To Stan,
you are a wizard indeed. Thanks to you and everyone here on this thread. The car started immediately. So now I know the battery itself is ok, and that my problem is a bad ground somewhere. So now look up all the ground points in the WSM and start looking at each one? I assume there’s an order of most accessible to least accessible points.

Originally Posted by SeanR

Start at the front of the car working your way back and do the battery ground strap last, your car will work wonderfully.

Originally Posted by SeanR

Start at the front of the car working your way back and do the battery ground strap last, your car will work wonderfully.

Originally Posted by Jason89s4

For and S4, but most ground points are same for S3.

Originally Posted by Shark2626

This is a fun thread! 😂

Originally Posted by abrescia

... If you don’t hear from me anymore I want to thank all of you for your camaraderie and assistance...tell my wife I loved her...