Electrical issue
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,084
Likes: 786
From: Lebanon Township New Jersey
Electrical issue
The needle on the volt gage in my 77 typically is just left of the red area while driving normally and sometimes goes into the red. It stays there for a few seconds then comes back down a little. This is with a new (rebuilt) alternator. I replaced the previous fairly new alternator because it was doing the same thing. This happens with the headlights and high beams on or off. The headlights flicker a little at times too. Have I gotten 2 bad rebuilds in a row or is there something outside the alternator/voltage regulator which causes this?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Either your battery is shot or the wiring to/from battery/alternator (including grounds) is corroded or has loose connection so that adequate current cannot flow. Check condition of wiring and wiring connections [power and ground]. Strip back the insulation just a bit at the ends to check condition of wiring. If no problems, change the battery.
You have a voltmeter. After starting the car, the voltmeter might read up to 14 volts (or so), but shortly come back to about 13 volts and continue to run there under normal driving conditions. At idle, it might drop a bit lower, because the alternator will not be putting out much current then. If you stay up around 14+ volts under normal conditions, it indicates that the alternator "thinks" the battery is low on charge (whether it really is or not). This is usually a sign of a weak battery.
You have a voltmeter. After starting the car, the voltmeter might read up to 14 volts (or so), but shortly come back to about 13 volts and continue to run there under normal driving conditions. At idle, it might drop a bit lower, because the alternator will not be putting out much current then. If you stay up around 14+ volts under normal conditions, it indicates that the alternator "thinks" the battery is low on charge (whether it really is or not). This is usually a sign of a weak battery.
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,084
Likes: 786
From: Lebanon Township New Jersey
7T1 - Thanks for your response. Battery is fairly new, but I will put a meter on it to check. I have redone most of the grounds over the years but I'll check those. The wiring at the alternator is original and looks good but I will have to look closer.
Melting Slicks
Joined: Aug 2012
Posts: 3,487
Likes: 83
From: Titusville Florida
This is coming from someone who knows very little about electrical systems so take it for what it's worth but have you checked your voltage at the alternator? if that's putting out the correct amperage then wouldn't that say it's in the wiring between the alternator and battery? assuming the battery is good.
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,084
Likes: 786
From: Lebanon Township New Jersey
This is coming from someone who knows very little about electrical systems so take it for what it's worth but have you checked your voltage at the alternator? if that's putting out the correct amperage then wouldn't that say it's in the wiring between the alternator and battery? assuming the battery is good.
