| Author | Message | ||
| MICHAEL MORETT (Thecarreaper)
New member Username: Thecarreaper Post Number: 4 Registered: 9-2003 |
another possibility is a "parasitic draw" ie something is pulling juice all the time and in effect the battery is always discharged and becomes " deep cycled " i have a way to check this though i havent had to do it in some time. 1) dont do this on a computer/ fuel injection car 2) remove NEGATIVE battery cable and securely fasten a test light 3) note that radar detectors, alarms, and stereos with " memory" will need to be turned off and have fuses removed 4) light should be off, as a test leave the dome light functional and then open the door to see if the test light comes on. then pull the fuse or bulb for the dome light 5) the goal here is for the test light to be off while the car is off. if it is NOT then pull fuses on at a time to narrow down what is pulling current. use a multimeter to read both amps and voltage to see what kind of draw there is, ie a big power wire will pull more amps than a small one without getting hot or causing a fire. once you find the system or circuit then you can trace wires and find what is draining the battery and possibly over working the charging system. i am sorry for the long post but i have had lots of 20-30 year old cars and they all develop the same issues over time. i hope this makes some sense and may help someone. michael | ||
| Mike Procopio (Pupz308)
Member Username: Pupz308 Post Number: 546 Registered: 10-2002 |
Do a quick archive search. I'd say five folks here have had their alternators rebuilt, at least--probably more like 10. As Michael points out, part of the game is finding the right (Bosch, I believe) voltage regulator (part number). Fortunately, all this has been done already and this info is well known. For the record, my alternator/VR was charging my battery at 17V for quite some time before it finally exploded. I now have a voltmeter gauge added to the car  . Very abnormal to go through a battery a year. | ||
| MICHAEL MORETT (Thecarreaper)
New member Username: Thecarreaper Post Number: 3 Registered: 9-2003 |
there should be a voltage regulator built in, but i will take a stab and try to help... i have had diodes go bad and voltage regulators that would work whenever they felt like it. you should be able to get the alternator checked on the car or if you are a wrench turner like me, pull it off the car and take it to a parts store and get it tested. its been my expierience on my collector cars to pay to have the original component rebuilt rather than getting a new one. its all bout the "numbers and codes matching". at 2000rpm and above is where most voltage regulators kick in but i am not an expert on f cars yet. a multimeter would be a good idea as old factory gauges can read wrong depending on temperature and vibration.good luck... michael | ||
| Mike Procopio (Pupz308)
Member Username: Pupz308 Post Number: 545 Registered: 10-2002 |
Mine 78 308 exhibits the same behavior. Recent alternator rebuilt and voltage regulator replacement. It's certainly not linear across the band; if I had to guess, it reaches a low point below 900 rpm, and is restored to the 13.5V at say 1300 RPM... Within that range it might be approximately linear. I think this is normal for 308s, since other have reported "slightly weakened headlights" at idle and this seemed to be accepted by other 308 owners. The battery-per-year thing is very strange though... Overcharging could cause this, or deep-cycling it could as well. If you've never had your 308's alternator rebuilt, they seem to universally require this attention (rebuild + new voltage regulator) right about... 20 or 25 years , if not sooner! --Mike | ||
| Bill McAlister (Wmcalister)
New member Username: Wmcalister Post Number: 19 Registered: 9-2001 |
I go through a battery a year. While I was monitoring the new battery voltage it would go from 11.9v at idle to 13.5v when the engine was reving. Is this normal? I would hope the system would be linear. Is the regulation in the alternator or is there an external regulator. Any suggestions? |