I left my 1984 928s sit for a week(the car does not like sitting even for a day) when i try to turn the car on all i get is a rapid clicking sound


the a.c which is usually stuck on is now off so I am thinking its a battery or other cheap porsche electric issue

 

Sounds like a dead battery to me.

 

That's a standard 'solenoid click'.

Dead battery.

If you battery is dead within a few days, you likely have a parasitic electrical drain of some sort.
There are a few circuits that are known for this.
Finding them is basic electrical diagnostics.

It's been covered repeatedly on here, a search will find all sorts of info.

 

Long story short, a battery maintainer; it's almost impossible to get the drain to zero. Also a model with alligator clips.

 

NOTE a battery tender, maintainer, or any other battery topping up tool, is not a replacement for a battery charger.
When the battery sees a big discharge these devices are not really good for returning the battery to fully charged state.
Remove the terminals then charge the battery with a 6 amp charger for 3 hours or more

 

Battery. I disconnect mine if its going to be parked up for a while. Depending on how old it is a deep discharge might finish it off. If it's old you may want to replace it and then manage it with a trickle charger going forward. I had a few breakdowns due to a bad battery.

 

First, figure out your voltage drain problem. This is not normal, and may not be safe. Keeping it on a trickle-charger to "mask" this problem will not make it go away, and what happens if you actually need to go somewhere and park your car for a day or so. You going to find someplace to plug in your maintainer? Your voltage draw with the car at rest should be no more than 30-40 milliamps.

Second, I cannot say enough about the Optima 400 Charger/Maintainer. Its small and "smart" and will diagnose, charge, recondition and maintain both AGM (eg. Optima) and wet (eg. standard, old school) batteries. I had two wet Interstate batteries that I had left for dead after trying to charge overnight with my old charger (which wasn't cheap), and this Optima charger brought them back to life. Plus you can use it as a maintainer.
(Note: it is not for "jump starting", it works but takes time. Prepare for overnight if it needs to do its thing on a fully discharged battery.)
Very good use of $89. It will pay for itself.

https://www.optimabatteries.com/en-us/battery-charger

Jason

 

 

Hello,

please check also the battery ground strap connection behind the tool plate... On my car the wing nut was loose when I had the same noise and no start recently.

Cheers

Hartmut

 

It is impossible to get the drain to zero. There's always a couple things drawing power (clock, radio constant power, alarm).

But getting the 'parked draw' down to manageable levels is not all that hard, although it can be a torturous path.

I can park my car for 2 or 3 weeks and not have any problems starting it up.

Also, the suggestion to check the ground strap is a good one. They can corrode under the insulation and fail. They will show continuity with a meter, but will not be able to carry the current needed to start the car.
You can check it by running a single jumper cable from the battery to a good ground.

You can also put a meter on the battery and see what it shows for voltage. Check it when sitting, then check it while cranking (it takes two people to do this). It should show above 12v sitting and stay above 10 or so when cranking.

 

To the PO - guessing you must be relatively young to not know what that sound means!