So I was about to head up to McMark's for the BBQ a couple weeks back, got in my car and the red charging light was on before I started the car (normal) and after I started the car (a problem).

The fan belt was present and tensioned, so I hoped it was the voltage regulator and not the alternator.

I ordered a Hella regulator from Pelican Parts and while it would connect with the board, the relay board cover would not fit on. The plug on the hella is not in the same place on the regulator as the bosch one.

But since it connected (at least!) I gave it a try. Turn on the key, but not started, and no charging light. Turn on the car, still no light. But also no charging. Voltage across my battery is almost 12v with the car off, and 11.5 with the car on. No charging.

So I ordered a new Bosch voltage regulator, and just installed it. Same thing. No light with the key on and engine off (no oil light either this time!), no light with the engine on either. Still no charging across the battery.

Hey, maybe the bulb(s) blew? I put the original, broken regulator back in, both dash lights light up when the key is on but the car is off, and the oil light goes out when its on, but the charging light stays on. And no charging across the terminals.

What gives? Did I just get two bad voltage regulators? Am I missing something?

Thanks for your thoughts, folks!

You need to check the voltage going into the regulator from the alt.

If low then you need a new alt.

but....


check your fuses too. I can't remember which one(s) it is, but I do know that if certain ones blow the alt light will come on as well. I believe it's #10.

I had the exact problem a few years back when I bought a new "solid state" voltage regulator. I found a good used old style voltage regulator and the problem was solved.

I thought that the bosch one I just got WAS analog.

But maybe its not.

If it's a fuse, the alternator light wouldn't come on when I switched back to the original (bad?) regulator, right?

If it's the alternator, how would that cause the different behavior with the different voltage regulators in place?

Thank you, everyone for your thoughts on this.

3 regulators not working says to me something else is broken TOO, but I don't know what it is.

Where did you get your good used regulator, Andy?

I'm ordering a new tech alternator that looks like it will be a bolt is setup. It's 150amps and internally regulated. If it works out it should be a great option.

Here's another fact.

When I switch from the old (broken/original) regulator to the new one, the oil light comes on when the key is on, but the engine is not. But just the first time you start the engine. Try it the second time and the oil light does not come on when it is supposed to (before the engine is on, but key on).

It was a long time ago I do not remember. Call over to Easy in Hayward, or High Performance House just south of you.

Its stuff like this that worries me when i think about replacing my Voltage Regulator.
The light stays on, till i rev it a bit then its fine.

Keep me posted, Mark. If I do end up needing to replace my alternator, I'd certainly consider that option.

Buying 3 brand new voltage regulators, none of which work, is not building my confidence in THAT solution!

I'll call up EASY once they open and see if they have a used one.

Thanks everyone for your thoughts on this! Much appreciated.

Did you check the fuses?

Also, what is the voltage at the battery with the car running?

Finally, if you still suspect the regulator, you can have then tested (even one of the new ones you bought) at the local FLAPS.

Voltage across the battery when running is .5v lower than at rest.

If the generator light does not go on before the engine starts, the alternator is not energized and will not charge (or at least that's what I've read).

That's the crux of this issue: if I get another voltage regulator to light the alternator light before the car is turned on, and it still doesn't charge, I'll check the alternator. But if the light never comes on, the alternator doesn't get a chance to charge.

Right?

Since the original regulator still brings on the light at rest, but the other's don't, it can't be a fuse can it? How does changing a regulator resolve a fuse issue?

Thanks, as always, for your thoughts, teeners!

I would have to spend more time to digest everything you posted above, but maybe this will help in the mean time:

The current through the alternator light is used to "boot" (to use a modern term) the alternator when it first starts spinning.
Once it is spinning the alternator provides this current itself so the current through the light is not required.

When the ignition is ON, but the engine is not running, the alternator light should be ON because the voltage at the front fuse panel is higher than the voltage at the alternator field winding.
So current flows through the light and through the field winding to ground.

Once the alternator begins spinning it will generate it's own voltage and will supply that to the field winding itself.

NOW the voltage at the alternator field winding SHOULD be the same as the battery and therefore the same as the front fuse panel.
So the voltage is the same on both sides of the alternator light so no current flows and light turns off.

If the voltage on the alternator side of the light is HIGHER than the fuse panel (for whatever reason) then the light will ALSO turn on because current is flowing through the light BACKWARDS.

So an off light means that the voltage on both sides of the light is the same.
An ON light means that the voltage on both sides of the light is DIFFERENT but you dont know which way.

Conundrum solved. It was the alternator. There was never anything wrong with my old analog regulator.

I did get THREE brand new voltage regulators (all solid state) that did not work. All of them failed to light the alternator light when the key was on but the engine was off.

Since the light energizes the alternator, it wasn't a valid test of whether the alternator was working or not--right? No charging could be because it wasn't energized OR because the alternator was dead.

So I went to EASY, where they told me that it wasn't the regulator, it was the alternator. However, I bought another analog regulator and voila--it acted just like my original one--light on before and after the motor starts. It was the alternator. Back to EASY where I got a used alternator.

I dug into the swap yesterday. Mark's tutorial on this site was a huge help! Figuring out that the sheetmetal has to move around quite a bit to get that bugger in there took me a second. After I got the carriage bolt in, I looked on the ground and saw the air gasket that's supposed to be on the front of the alternator. Practice makes perfect.

Key goes on, red light, engine goes on, no red light. Success!

Many thanks to everyone who chimed in with suggestions--especially that solid state regulators might not work very well. 3 brand new parts that don't work is hard for me to believe. That's how naive I am!

One thing.

The alternator I bought had openings on the sides of it in two places on the back side--where the back cover with the wires goes on.

I'm guessing that this alternator had a different back cover, or maybe some little rubber bits that filled the gaps. It looked to me like the original had taken some effort to seal off the hot/wet side of the alternator, so I duct taped the gaps on my alternator.

I bit hoopty for a Porsche, I know.

Are these openings supposed to be closed? Are there rubber bits? A different cover?

both alternators side by side