ammeter

[airlifter]

At times the ammeter will go negative and stay there for a while and then come back to positive. Sometimes it stays negative long enough to make me wonder if I will get home. This happens a speed or at idle. It doesn't matter if there are accessories are on or off. The car does not have a voltage regulator. I am thinking that it is built in to the alternator. Any ideas?

I had planned to update the alternator this past winter but I had to rebuild the front suspension. I might be doing it pretty soon.

Thanks, Pete

 

[Got_All_4]

sounds like my wife!!!

 

[angelfj1]

what make and model of car?

 

[Geo Hahn]

Profile indicates he has a 1969 TR6.

Alternators and wives are mysterious subjects for me (though I at least have one of the latter).

 

[DNK]

Why do you think it is the gauge?

 

[TR3driver]

How far negative does it go? Does it change if you turn the headlights on or off?

If it is only somewhat negative (and goes much farther when you turn on the headlights), then it likely is the alternator or the wiring to it (or the regulator inside the alternator). I would start by checking the wiring carefully, as it's both easier and less expensive to fix. Your original alternator I believe would have had 5 terminals on the back; but there is a good chance it has been replaced with a later unit with fewer terminals. If so, there may be some dubious connections where the original wires were adapted to the later alternator. There can also be problems inside the junction block where the heavy brown or brown/red wire goes. And I don't particularly trust those quick connects; I've seen them get hot and fail many times (though when it happened on my Stag, it took part of the regulator with it).

If the ammeter is going all the way negative regardless of what is turned on, then you have an intermittent short someplace. It could be inside the alternator, but there is no reason that would be any more likely than dozens of other places. Last time it happened to me, one of the wires to the (missing) wiper motor was flopping around and sometimes making contact with the body.

 

[airlifter]

The needle goes more negative as I turn on more stuff I turn on. Sometimes when I turn the engine off and restart it will come back to positive when restart.

The connections on the alternator sounds like a good place to start.

 

[LarryK]

Regulators are easily replaced, so are the rectifiers. Take apart and replace, put together. Look in a manual, there is a test procedure to tell you what's not doing it's job.