Charging system help needed

[DougM]

The car is an '86 930:
Had alternator rebuilt about 3 months ago and no problems since. This past weekend, I drove to a track event and the next morning, my car was dead in the hotel parking. Bump started the car and drove 30 miles to the track with no problem. Turned off car and it was dead as a doornail again. I replaced the battery and all was well for the weekend as well as the 180 mile drive home. I took the car out today and noticed all my electricals going dead on the way home and by the time I reached my garage, nothing worked. Turned the car off it is dead again.
Before I go in again and pull out the alternator, I wanted to check if there is anything else that can be causing this. I had my AC running and noticed that it actually blew cooler when all the other electricals wouldn't work right as I was pulling into my driveway.
Any suggestions?
Thanks

[Netspeed]

The A/C blew cooler or did the blower motor have more volume?

What part of the electricals didn't work? It almost sounds like you're running on pure battery power and nothing from the alternator. Did you get around 14volts at the battery when the engine was running?

[911pcars]

Assuming the new battery is good and that connections to it and vehicle are good, there are two possibilities:

1) Alternator not charging
2) Massive current drain through the system when OFF.

No. 1 is easier to verify. Connect a voltmeter to the battery posts. With a fully charged battery, it should read around 12.6 volts or better. With the engine at ~2000 rpm, charge voltage should be 13.6+ volts. If not, you have a charging issue.

Try the above first, then let us know. Checking for parasitic current drain requires another set of procedures (also covered in numerous threads in the archives).

Sherwood

[DougM]

I did an errand and on the way there all was well. On the way back it ran well, but when I was close to home, I raised my windows to turn on the AC. They went up extremely slow. My radio would also not turn on, no sunroof...nothing. Turned on my AC and it blew much colder than usual? Pulled into the garage and all electricals would not work before I shut the car off. Turned it off and the car would not restart.
I will have to put a trickle on the battery before I can get any readings.

If it is still the alternator, I just can't imagine how a new battery can last through 3 track sessions and about 300 miles of driving with the lights, radio and wipers on over the weekend, then today, function perfectly until the until the last few miles.

[Netspeed]

It might be an intermittent problem with the alternator. Maybe like 75% not working and 25% working.

I agree with testing for a voltage drain too.

[Jon Merck]

I just went through this, lots of info if you do a search. Could be as simple as a loose,dirty ground or as expensive as a rebuilt altenator.