Suddenly battery appeared flat at morning. It was one year old, one year warranty WalMart unit, so I went there and bought a new one, anyway that is one year deal.
Worked nicely for a week, then suddently battery flat down at morning. Jumper Start and went back to WalMart to check everything. Mechanic there used a portable analyser unit, said battery was ok, alternator was not
100%.Took alternator to a repair shop, they tested said alternator was not bad, but it was 8 years old, so I asked them to replace regulator, brushes, diodes, etc. They replaced everything inside, including bearings. Alternator now is supplying 145+ Amps, ok.
One week later battery flat down at morning. Car needed to fix water pump that was damaging serpentine belt, took to the mechanic and asked him to check for this once a week battery flat drain. That mechanic is not specialized in electric, but he said somethign connected to ALARM fuse is draining more current than expected.
Once at home I went after that. Found that ALARM fuse feeds energy to interior lights, chime, radio and "passive restraint", what a heck it could be I don't know.
I found out that the door locks energize some magnet while the doors are open, keep energized for 30 seconds after door are closed, after that the power consume at the ALARM fuse is minimum.
In middle of this battery problem I replace the radio with a JVC CD player, so I found the ins-and-outs of the panel for cables. Removing the JVC current on ALARM fuse reduced from 20mA (0.02A) to almost nothing. But 20mA I guess is not that bad for a CD player to keep clock and holding memory setup. A battery would take a month to discharge with only 20mA of drain.
Yesterday battery was really bad, middle charge, around 7V. I installed a lamp in between the battery negative pole and the negative cable, measured the voltage drop around the battery. Lamp is 6 Ohms of resistance, it developped pulsed from 1.5 to 2.2V over the lamp after 2 minutes of door closed. Found out that the CD player was flashing the pannel on and off. I guess it was complaining about the low voltage from battery, right now all those players are fully microprocessed and they can sense it and report in some way. Removing the CD player connector current went down to less than 5mA from the battery. Those 2.2V over 6 ohms, is around 300mA (0.3A) current consume, but even so it would take many hours to drain a fully charged battery to a state of only 7V. It was not the case, it happened during the night. Even so, those 300mA was the "error report" from the CD Player, and not the regular 20mA consumed while ignition key is off.
Found at the JVC CD Player documentation, an yellow wire that is contantly connected to +12V for keeping power to the device even with ignition key off. Removing this wire from the connector reduced battery consume to only 5mA, that is probably the consume from the Engine COmputer.
After battery was fully recharged with a power transformer, that CD player flashing state was not anymore. Power consumed by the radio was half amp playing or only 20mA after turning ignition switch off.
Using the lamp between the negative pole of the battery and the negative cable, measuring the voltage drop over the lamp, I was not able to identify ANY excessive current that could be sucking battery juice during the night. All I have is that 20mA from the CD Player. I was expecting to find some bigger drain current from the battery, then removing fused one by one until locating source of short circuit or something like that. Nothing was found.
Returned to WalMart to complain about a possible intermitent bad battery. They again tested battery and alternator, battery still ok, but now alternator was also ok. They told me that some short circuit in the car is draining battery during a parking state.
Something is happening, not always, some nights. Parked for around to 6 hours is not a bad deal, but if I keep the car parked for more than 18 hours it is better to start to worry about a jump start.
I went to Discount-Auto-Parts and Auto-Zone stores and tried to find a decent manual for this 1993 GrandAm, mostly looking for the electric diagram, but they don't have anything that worths the price. Nothing that says "THIS IS THE DIAGRAM FOR A 1993 GRANDAM 6 Cylinders"... just some generic Pontiac, and didn't find any that had at least the ALARM FUSE on the diagrams.
I really need some help, since it seems that nobody is able or interested in solve the problem. WalMart is always saying battery is good. Alternator is charging ok, but some is sucking battery and bad.
This morning battery has absolutelly nothing, the internal lights were not even dark dim, they are totaly off. It required an external charge of 8A for about 2 hours to allowme to turn on engine (I don't like to use jumper cables when battery is that much flat - can damage other alternator, or even this alternator by excess of charging current).
I suspect something goes bad after car cools down, will try to skick and check current drain in middle of night, but it is getting ridiculous.
I am pretty lost, any help will be much more than welcome.
Wagner.