Just changed the radiator and got her back on the road after two weeks. When I went to start, she almost turned over, but then the tick, tick, tick.

A quick jump start and she was back in good form.

I drove her to the office, she sat all day, then I drove her home, pulled into the garage and left for the night.

This morning when I got out there, the clock was going, but when I turned the ignition, I heard one click and then no power ... no even enough to keep the clock going.

I jumped her and she roared right away. No charging time needed, which leads me to suspect the battery wasn't dead. I drove to the office and just went out a bit ago to turn the key again and the same thing happened:

click ... no power ... no clock.

Thoughts?

 

With the engine running, check the jump posts in the engine bay for voltage. Should be about 13.4V. If significantly lower - either the alternator is disconnected (or connections are dirty/loose) or not putting out enough juice. May want to also verify the connections on the battery itself in the back. Make sure there is no corrosion and the connections are clean and good, and that the ground strap is good.

 

Our cars are very sensitive to weak batteries. My now-gone auto S4 once would start and run off a jump, but the moment I removed the cables, it would die. I recommend you at least try swapping with any other battery to run it a day and see.

 

Speaking of which ... that S battery is a MASSIVE DEAD WEIGHT .. what the F were they thinking ... in a sportscar yet.

 

Careful with jump starting too, the LH might get spiked

 

I went out to the parking lot with a portable charger and noticed the ground was loose. I put it back down and power was back and she roared away.

But ... when I pulled the ground post off, she died immediately. Does that mean battery is about to die?

 

I had the same thing happen to my car- turned out to be a bad ground cable from the battery to the chassis. The solder corroded between the braided cable and the terminal, and eventually lost connection. No noticeable defect looking at the cable, but when I fiddled with it, the power came back on. Being on the road, I just took it off the car and hammered the crap out of terminal and put back on- got me home, and I since replaced it.

 

Not necessarily, but it may indicate that your alternator is toast. As a rule, NEVER pull a battery positive or ground cable while the engine is running.


At this point, you can verify that the car is charging by checking the vltage between the batery positive and ground. Should be 13.5 to 14 volts with the engine running. If it is less than 13, take a serious look at the alternator.

Assuming that you found good charging voltage above, check again after the engine has been off for an hour or two, and you should see a little more than 12 volts (minimum). If it's less than that, it's probably time for a battery. You can get a battery hydrometer to check for a weak cell or a weak battery, to confirm your meter reading. My limited history with my '928 suggests that three years is a practical life expectancy in my service. If you are beyond four years, it will soon be due for replacement if it isn't already.

 

Your alternator actually DEPENDS on the battery 'pulling-down' the voltage that it produces, it's a VERY bad idea to run a car with either terminal disconnected.

If either post is loose, galvanic corrosion can -over time- make the junction high-resistance. -Without getting too-deep into basic ohms-law and kirchoff's-law, suffice to say that it's a common problem.

From the little that we know, I'm inclined to say forget the charging system. Your car pulls current when it runs if the battery is bad, you'd be stranded while driving. -Sounds to me like a high-resistance in one or other lines from the starting power source. The symptom is that the clock (which draws miniscule current ) is momentarily put in parallel with the starter motor (which pulls a lot) and the power dies. If the battery still has voltage at the posts, you have a high resistance somewhere.

Check for corrosion (dull, greeny-grey strands in the copper cable) at both terminals, specially the one going from the positive terminal to the starter motor.

Keep the terminals tight, and apply a little jelly to the posts, to keep the air away.

 

If you value the electronic devices in your car I would NOT repeat this little experiment. You are very fortunate the car starts at all.

 

I always shut off in the inside stuff like the fan switch, move the lever to O ect. One morning I woke up morning to find that it was dead.

Put the charger on it for a day, got in it later and noticed that my fan was blowing, I had to jiggle the slide switch a few times but it finally shut off and now no battery drain, it's happened a few times.

I think we all have little electrical gremlins that live in our cars. No pesticide to kill them, but I'm hoping to corner one of the lil bastages and cut him out of the loop.

 

I agree with the above regarding the necessity of the battery in the circuit and also the potential for damage by disconnecting the battery with the engine running.

I suspect you had a bad connection at the battery, but when you jumped it you bypassed that problem area so it fired right up. The battery connection was just good enough to keep the system functional when running, but the current draw to start is much higher and your poor connection couldn't carry the load. As a result the connection you did have was lost and the clock (and everything else) lost power.

So clean and tighen all the connections at the battery and monitor for additional symtoms. You may be lucky and the connection was the only problem.