Alternator Again?

[Deanj]

The new exhaust manifold gaskets are on and on the same day the GEN light came on. This 1960 is starting to wear.

With only the headlamps on and 2 miles from home, the GEN light came and started getting brighter as engine RPM increased. In a matter of seconds it burned out (I'm sure). Made it home and checked to find the alternator is not charging the battery.

I haven't confirmed if the 80amp fuse blew or the alternator is bad, again for the 3rd time in two years. I just confused how the GEN light kept glowing brighter until it failed.

Time for another tear down.

Dean

[jopizz]

Once your GEN light burns out your alternator will not charge unless you have a resistor wired into the circuit. Replace the bulb and see if it starts charging.

John

[jopizz]

When it comes to alternators I try to stick with name brands (AC-Delco, Remy, Motorcraft). I haven't had much luck with the cheaper ones that Autozone or Advance Auto sell.

John

[simplyconnected]

... I just confused how the GEN light kept glowing brighter until it failed.

That happens when the voltage regulator (in your alt) fails. Voltage regulators are sold separately and they are inexpensive.

Also check the connection. The voltage regulator has a separate wire that comes out of the alt, then goes back into the alt. If the connection is loose or off, the alt won't know when your battery is at 13.5-volts (provided your GEN lamp is good) so it keeps charging until something fails.

John's advice is good, check your GEN lamp.

What model is your alternator? - Dave

[JohnG]

if you have relatively modern alternator with the voltage regulator built in to it, can you by pass or eliminate that internal regulator and instead use your own external one?

[jopizz]

There are many alternators that require an external regulator if you wanted to go that route. However, considering how inexpensive it is to replace the internal regulator if it goes bad (around $10) there's not much reason to modify it to take an external one.

John

[Deanj]

There are many alternators that require an external regulator if you wanted to go that route. However, considering how inexpensive it is to replace the internal regulator if it goes bad (around $10) there's not much reason to modify it to take an external one.

John

Good advice from all of you. I destroyed the internals of my old external voltage regulator so it wouldn't even have a chance of conflicting with the internal unit in the alternator. It remains for looks only.

Turns out the alternator definitely when full field to burn out the GEN light. It got super bright as RPM increased. Why didn't the fuse blow? I have an 80 amp fuse on a 4 gauge wire.

Now...I went to redeem the Limited Lifetime warranty at O'Reilly's. No go, that only pertains to the original alternator and not the "replacement". They have no repair parts, so I bit the bullet and bought the only alternator they had-the same one that probably isn't worth a hoot. If this happens again, I got to get a better rebuild.

Surprise! Without a GEN light I get 14.6 Volts on the battery.

So I will replace the GEN light, but it seems to charge without one.

Dean

[JohnG]

However, considering how inexpensive it is to replace the internal regulator if it goes bad (around $10) there's not much reason to modify it to take an external one.

John, you have answered my question by a different path. I take it that I can dismantle a non producing, internal-reg alternator and remove that component, and replace it. What would I ask or look for , for the $10 replacement?

I have had more than one alternator over the years which, by my sense, had defective regulator but still good armature/fields. So this is good for me to know about.

johng

[jopizz]

It depends on the type of alternator. I was referring to the GM 10SI alternator that Deanj has. Those alternators were used on most GM cars from the late 60's thru the 80's. Those are the ones I'm most familiar with. It's best to look up the part number if you don't know the specific application.

John

[Deanj]

Amazing how little goes without a hitch. With the new alternator in place, I replaced the burned out GEN no. 57 bulb and started my car and everything was good. GEN light went off with the engine starting. Tied up the wiring, cleaned tools, and shut hood. Started car and the GEN light was on.

Really? Must have known I closed the hood. Tore wiring off and checked everything for continuity. Re-routed red voltage drop sense wire to rear BAT terminal of alternator-mostly because I didn't know what else to do.

Voila! Everything works. I am amazed I didn't go into a fit and just went about trying to solve the problem. I think it was the shock that it might have been a bad alternator right out of the box.

Dean

[jopizz]

Re-routed red voltage drop sense wire to rear BAT terminal of alternator-mostly because I didn't know what else to do.

Voila! Everything works. I am amazed I didn't go into a fit and just went about trying to solve the problem. I think it was the shock that it might have been a bad alternator right out of the box. Dean

I don't know where you had the red wire run initially. I've seen people run it all the way to the solenoid but that seems like overkill. Most diagrams show it looped to the BAT terminal.

John

[Deanj]

Yes, I had it connected to the starter relay. I remember you suggested that it loop to the rear BAT terminal, and so I re-wired mine that way. I keep reading all kinds of suggestions about where to connect it. I don't know how much the voltage will fluctuate depending on its "sensing location".

Dean

[jopizz]

I keep reading all kinds of suggestions about where to connect it. I don't know how much the voltage will fluctuate depending on its "sensing location".
Dean

I've read the same things. I had it looped to the BAT terminal on my '59 and I never had a charging issue. Some people say if you have a lot of options not to run it that way. I guess whatever works.

John