djellum Posted October 16, 2012 Share Posted October 16, 2012 Hey, start from scratch just in case, 87 carbed GL wagon, 5 spd dual range. so last night all of a sudden I started getting dimming headlights at idle, and the gauge dropped to about 10 volts unless i revved the motor up to about 1500. today I swapped batteries with my truck, same condition, running with the battery unhooked the volts jumped around between 14 and 8 all erratically, but it did run. took the alt in and had it checked, passed with flying colors. its never given me a second of trouble with the charging system till all of a sudden last night. Its always pegged 14v all day. added a small ground strap with some extra wire I had, and it seemed to improve so Im gonna check my grounds. the main battery ground goes down to the bell housing, but I cant really get at it without removing the heater hoses. if this was any of the other cars I have found this problem in I would just run a good sized auxiliary ground to the body near the battery and replace and clean some of the aux straps, but I don't know if there are other hookups at the connection under the hoses that I need to worry about. Ideally I would just get a new clamp and run a new second ground to the body and call it a day. Can grounds just go faulty all of a sudden like that? Ive seen charging systems get weak from bad grounds, but it was a stepped process. test or not I'm still suspicious of the alternator, but I want to exhaust options before dropping $70. Link to comment Share on other sites More sharing options...
The FNG Posted October 17, 2012 Share Posted October 17, 2012 (edited) I would jump straight to the alternator, honestly. If I am correct, it should read just higher than 12VDC (between 12.7VDC and 14VDC) between the output post and ground. Because voltage is potential energy (like water pressure in a kinked hose) it should always remain constant at the posts, although amperage may change in a completed circuit. I guess what I am saying is that varying voltage at the output of the alternator would indicate a bad alternator or internal voltage regulator. Also, instead of paying $70 for one, buy one from somebody on the board for much less Plus you will know it's good. A couple more thoughts, make sure to clean your grounds and connecting points with a wire brush or something similar and check your alternator belt for hard slick surfaces and proper tension, it could be slipping. Edited October 17, 2012 by The FNG Link to comment Share on other sites More sharing options...
TomRhere Posted October 17, 2012 Share Posted October 17, 2012 Main battery ground is a single wire at the attachment point on engine/trans. Shouldn't need to remove heater hose to get to it. As said, clean all ground points you can find. Doesn't hurt anything to add extra grounds either. Link to comment Share on other sites More sharing options...
djellum Posted October 17, 2012 Author Share Posted October 17, 2012 I picked up an extra battery cable and a clamp on terminal. gonna hook it up with the standard battery to block, and another wire going to body ground. have a few ground straps to clean up but they aren't bad. Idk about whats normal but my ground now hooks in just under the heater hoses, the rubber insulator is actually pinned in by them. ill hook up the ground but if it doesn't fix it completely Ill just replace the alt. Link to comment Share on other sites More sharing options...
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