Helpful Tip
 

This won't solve your current problem but once it's resolved this might help identify problems in the future. Someone mentioned that in their infinite wisdom Porsche didn't give us a voltage gauge.

Several years ago I bought a Beltronics RX65 radar detector. One of its features is a setting that will monitor and display the charging voltage of your car. It constantly shows charging voltage until a radar signal is picked up. It's been very useful in watching my charging voltage and how it changes under different load conditions.

So, we kill two birds with one stone. A radar detector (although we don't need one...:D) and a voltage meter.

Check your radar detector to see if it has this feature.

Valentine One...the best self defense weapon since the single action colt revolver...cool of Beltronics to do this, tho. Plug in digital voltage meters are becoming plentiful as well...think I've seen them for less than $20.

Here is a pic of a portable voltmeter that I bought several years ago. Works great!!http://forums.pelicanparts.com/uploa...1279474629.jpg

Thanks. You know, I actually have one of those gizmos but never stopped to think of pluggin it in!

I guess I'll get a decent indication even tho it is a bit remote from the battery.

I'll do it today, right after I patch some peeling paint, put up some trim, and pull the power steering reservoir off of the Camper...

Good thread Paul. Will have to try this as I have a dead (3.5 v) Optima that I hate to lose.

3.5v? i don't think you ill be able to recover that one but you never know.

Checking battery
 

:cool:First, with engine running, using a DVM, check voltage a terminals. If it isn't 13+ volts then your alternator is the problem. Rev engine a little as some earlier alternators have a threshold and don't charge at the lower idle RPM's.

Second, trying starting car with headlights and blower on. If lights completely fade out (and alternator is good), then you have a dead (or dying) battery and you need to replace it.

Thirdly, using the ammeter on DVM, with key out of ignition and doors closed (you want no amperage draw), disconnect either terminal and put DVM in series with cable. You will get a minute draw (from radio memory and/or clock). Any substantial amperage indicates problem. That's when you go to fuse box and pull each fuse one by one (while watching amp reading) and hope you get lucky and find faulty circuit.

It's not really necessary to rely on the parts store to troubleshoot. After all, they are not the one who gets stranded miles from home at 2:00 AM Sunday morning with a completely dead battery.

I have troubleshot many a battery and the above troubleshooting has never let me down.

Good luck.

In addition
 

If lights do fade out, the starter could be drawing excessive current so you want to check that also.

- turns out the cig. plug is only hot on the running circuit; not the start crank circuit

battery reads 13.0 V after weeks of sitting on the maintainer (static)

drops to 12.7 V after I crank the car a bit

Randy,

And what does it read after the car starts?

If you are charging, you should see something like 13 to 14.5 volts.

If the battery has 12.7v after cranking the car, the battery is in good shape.

- that's what I think; I might bet that none of this is a battery problem -- instead, it just so happened that getting a jump start coincided with some other intermittent problem not happening (maybe the switch is going out)

Have not started the car - been sitting (while I worked on other stuff) & float bowls are dry.

If u only get this prob after the car has been warmed up, I'd check the starter & solenoid. If the supply to the solenoid is fine, check connections, which tend to get corroded down by the starter. Solenoid failing can b showed up by heat as well.
For myself , I had the starter serviced and solenoid checked fine. I then redid the crimped eye end terminal. This hence was the final fix

no the car had been sitting for a while in cool/moderate air -- for maybe 1/2 to 1 hour after running it; alt newly rebuilt & tested; all cables in xlnt shape not long ago...

The Bosch 911 starter soleniods are known to have issues when hot. This goes as far back as the old VW beetles. Back then you'd have to tap the soleniod with a broom handle and that would "cure" the issue of a no-start.

So there isn't anything wrong with you battery. It simply didn't move the soleniod with its 12V resting potential. By the time you had rigged up the jumper cables with the donor car reving the voltage went up to 13.2V and that made the difference.

If anything get your starter rebuilt.

Ingo

Exactly what I use my detector for,..moreso than radar/Laser sensing!!!!! It once alerted me to two (2) +16 volt conditions prompting installation of a new alt and VR. Has kept me from having to install a voltmeter (i.e., MOD) in my car. You damned well don't won't to "rail" the DME power buss, for sure. Loren has reported some DC voltages that are quite DME-Death-Producing.

On a sidenote, anyone using this metering methodology would be well-served to VERIFY the instrument DC voltage reading AT the detector measurement point (cig lighter jack) VERSUS what's seen (measured) AT THE BATTERY TERMINALS. One could easily experience a voltage drop through the cig contact elements, rendering a lower voltage than what's actually happening AT the battery. In my case, it's quite small differential @.1 VDC....(whoooowhooo,..great wiring contact!!!!!!!). I trust that radar detectors' voltage readout with all my heart!!!!!!!!! And watch it as often as the oil temp gauge.................


I'm with Ingo on this no start after warming up issue,...gotta' rule it out, somehow..

Best,

Doyle