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Why does the voltage drop suddenly then just as suddenly jump back up to 14

(1994 Buick Regal)
in Indianapolis, IN on December 18, 2013
This is a constant issue for the past 6 months. It happens under different situations. Ideling, driving slow, on highway, cold, warm. it doesn't seem to be consistent with any particular condition. New battery. Alternator was removed & tested fine. battery connections are clean. Grounds seem to have good contact. Check engine light stays on. When volts drop, gauge does not react either way when increasing rpms. This has never affected start up. However today while idling at a light, voltage dropped, car died & would not restart. Acted as if battery was drained. Jump started immediately. Turned key off & the car started on its own fine. Strong battery. After about an hour, car wouldn't start again., as if dead battery. I have been driving for months with this voltage fluctuation but today is the first time it stalled & wouldn't restart. can the alternator work intermittently? Are there fusible links that could have intermittent connection?
Displaying 1 answers & 3 comments
Popular Answer
on December 18, 2013
I think this car has two cables attached to the battery positive terminal, make SURE they both are clean on all contact points and tight. Ground cable as well! Have alternator tested under a load, same for the battery.
on December 18, 2013
Yes. It does have 2 cables to the positive terminal. I noticed that the cable that runs from the battery to the jump start lead, I believe this is at the ecu/fuse box.... the plastic mount is cracked that holds the positive jumper lead. The connection looks good & clean with the cable, post & metal that comes from the control/fuse box but the mount is definately cracked
on December 18, 2013
Remove, clean and tighten ALL connections no matter how they look! Common problem with this set up. Remove neg. cable first, install it last.
on December 18, 2013
No good. Every connection from battery to starter to engine block ground to alternator has been disconnected, cleaned & reconnected. Car started fine but still has the fluctuating sudden voltage drop the back to normal then drop again. I had the alternator load tested & it apparently was fine, however...just now, I discovered that when the voltage is at 14 & no check gage light on, I can disconnect the battery & car still runs. Next I reconnected the battery, waited for the voltage drop, disconnected battery & car died. Isn't that a classic bad alternator test. Can the alternator work intermittently like that ?
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