Bad alternator?

[BadDog]

My amp-meter was almost pegged all the way to work this morning, so I went over to the local Autozone to see if my voltage regulator was bad. We ran the diagnostic, and the machine said the problem was a "bad diode pattern", which the mgr interpreted as a bad alternator. At idle, the ampmeter is right in the middle, but bounces when the turn signal is on, dips when headlights are on. Past about 2,500 RPM or so, the ampmeter is reading about +50 unless I turn on the headlights, which knocks it down a little bit. They said my alternator is only putting out about 30 amps right now when it's supposed to be 50...

They can get me a new alternator tomorrow, which is fine. I'm just wondering whether I should drive the car home tonight (30 miles or so) and put on the new alternator at home, or leave it at work, borrow a car to drive home in, and put in the new alternator in the parking lot tomorrow. I'd be more comfortable putting it in at home, but I don't want to run the risk of boiling my battery by driving it any more than I have to. On the other hand, I don't want to screw up my car when trying to install it tomorrow and have to have it towed all the way home....

And should I get a new regulator and battery while I'm at it? The battery looks pretty old...

[Phacade]

Its never a bad idea to go with a new battery and regulator when springing for a alternator. I would exchange them at the same time and then watch the needle close.

[2ManyZs]

The factory rating for the alternator is 45 amps, so if your is only putting out 30 it is a bit weak. So being that it isn't supposed to be 50 at least you know yours is not as bad as you thought. I'd change the voltage regulator first, check to see what the gauge does then, and if it still acts up then change the alternator.

[BadDog]

so it would be a bad idea to put a 50-amp alternator in? That's what Autozone can get for me tomorrow (Duralast?)... along with a new regulator (Wells?) and a battery.....

I guess what I don't get is if it's my alernator that's bad, and it's only putting out 30 amps, why does my guage read so close to 60?

I also noticed a discrepency between what their "tester" equipment showed my RPM as (read it from the Negative battery cable somehow???) and what my tachometer said, i.e. he goes "let it go down to 800 RPM" as his machine reads around 1120... I look at my tach and say "my tach says around 800 right now"

[2ManyZs]

First off, the 240 tach is the more innacurate of the tachs in the early cars. That's one reason most people update to a 280 tach as its a bit more accurate.

The regulator may be making the difference in the gauge reading. It is trying to make up for the weak alternator. I'm not sure about that, but it seems logical.

A 50 amp alternator should be OK, since the factory rating is 45 and it's possible you won't get the full 50 anymore than you might get the full 45 out of a factory replacement. They are rated at that, they may not always provide that rating.

[BadDog]

Oh, OK, I just wanted to make sure I wouldn't fry my regulator or something :-)

[BadDog]

Well a new alternator hasn't changed anything... I pulled the voltage regulator to see if I could check it, but I don't think it's original, and it's all sealed up (no coils like the Chilton's manual shows). I did however find while checking/cleaning wiring connections that there's a wire corroded so bad from the hiring harness that it won't stay in the connector block. Does anybody have a pinout or diagram of the connections from the wiring harness to the voltage regulator?

The wire that is bad is a yellow wire coming out of the wiring harness that runs along the top of the frame rail. It's part of a group of wire that go into a plastic connector, with a single (blue?) wire going off to a diode mounted next to the regulator, before the connector. Of the wires coming out of the other side of this connector, all connect to the connector for the voltage regulator, except one yellow wire which goes to the firewall (to the ammeter?)

I'm wondering if I should just splice around the first connector for this one wire and see if it solves my problem?

[BadDog]

Sone of a gun, that was it!!!!!!! I guess this is another one I can chalk up to degreasing my engine.. and I had *everything*that could be covered, covered when I did it! :stupid:

Now I've got to figure out a more permanent solution than a couple inches of thick speaker wire tentatively jammed into place :stupid: