Challenger Posted July 22, 2008 Share Posted July 22, 2008 I did some searching and found that it wasnt good obviously and that it can have some bad affects on the battery. Ill have to wait till I get all my lights in to test for brightness or if they get blown out. Is there anything I can check that might show where the culprit is? Thanks, btw car is a stock 78 l28. Quote Link to comment Share on other sites More sharing options...
hughdogz Posted July 22, 2008 Share Posted July 22, 2008 Sounds like it may be a bad voltage regulator. If you have an L28, then the alternator is probably internally regulated. Take it to the parts place to have it checked...it's free, right? Quote Link to comment Share on other sites More sharing options...
Challenger Posted July 22, 2008 Author Share Posted July 22, 2008 Thats what I read so Ill try that. I was just outside and with the key out it is at a little past 12v. Is that normal? Im actually kind of happy having a mechanical issue for a change! Quote Link to comment Share on other sites More sharing options...
rvandivort Posted July 22, 2008 Share Posted July 22, 2008 yeah, You have an internal voltage reg on the 78 L6 alt. Earlier models had an external. Check as above. Good luck, Roger Quote Link to comment Share on other sites More sharing options...
z or bust Posted July 22, 2008 Share Posted July 22, 2008 OK tying not to thread jack but I have the same problem but I put an alternator from my 83 onto my 77. Should I just unplug my voltage reg? But I still dont understand why its pegged at 16v? Quote Link to comment Share on other sites More sharing options...
Challenger Posted July 22, 2008 Author Share Posted July 22, 2008 Does yours register at around 12 when off? Mine was just over 12 just sitting there so I unplugged the battery, not sure if it was doing harm. Quote Link to comment Share on other sites More sharing options...
ktm Posted July 24, 2008 Share Posted July 24, 2008 Check the battery sense wire coming from the alternator to a battery hot source, typically found off the wire from the starter solenoid back to the harness. I can't say for 280zs, but for 240zs this wire had a fusible link which could pop. Check this line/fusible link. If the alternator does not "sense" voltage from the battery, it will overcharge. Quote Link to comment Share on other sites More sharing options...
z or bust Posted July 24, 2008 Share Posted July 24, 2008 Yeah its at 12 when off but the minute I turn the key in the on position it peggs at 16v and the light comes on. Quote Link to comment Share on other sites More sharing options...
calpoly-z Posted July 25, 2008 Share Posted July 25, 2008 Are these voltage readings from off the stock gauge? If so then you probably don't have a problem. My 77 has always read at around 16v with the motor is running, and this is with multiple alternators and even two different (stock) gauges. Mine also reads at about 12.5-13 or so volts when the car is off. I vaguely remember reading about this a couple years ago, and that its a non-issue. Quote Link to comment Share on other sites More sharing options...
calpoly-z Posted July 25, 2008 Share Posted July 25, 2008 I also ran the same cheap O-Rielly battery for over 5 years. So I highly doubt there is an overcharging issue. If you want to verify that you're fine, just use a multi meter across the battery posts when the motor is both off and running. when off voltage should be between 12-13 v and running/charging should be around 14.4v Quote Link to comment Share on other sites More sharing options...
z or bust Posted July 26, 2008 Share Posted July 26, 2008 Are these voltage readings from off the stock gauge? If so then you probably don't have a problem. My 77 has always read at around 16v with the motor is running, and this is with multiple alternators and even two different (stock) gauges. Mine also reads at about 12.5-13 or so volts when the car is off. I vaguely remember reading about this a couple years ago, and that its a non-issue. Ok well then i'm probably ok cause thats exactly what mine does. Quote Link to comment Share on other sites More sharing options...
jtl260z Posted July 28, 2008 Share Posted July 28, 2008 Thats what I read so Ill try that. I was just outside and with the key out it is at a little past 12v. Is that normal? Im actually kind of happy having a mechanical issue for a change! 12.5 to 14.5 is normal. When your car is off and your battery is fully charged it should read between 12.5 to 13 volts. Double check your voltage at the battery, if it still seems high, check your fusable links and if that's not it you might need to adjust or replace your voltage regulator. Quote Link to comment Share on other sites More sharing options...
Gollum Posted July 28, 2008 Share Posted July 28, 2008 Yea, mine can read anywhere from 13 to WAY above 16 on the stock guage. Been running just fine for 6 months + now. It's a guage issue, not a voltage regulator issue. At least for me it is. You should still check the battery with a multimeter when it's running though. Just to make sure. Quote Link to comment Share on other sites More sharing options...
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