530D wont charge after replacing alternator
 

My starter went out, changed it. Had to sync ews with dme, did that. Drove, wouldnt charge, replaced the alternator, ran fine the evening i replaced it. Next day on my way to work, it stopped charging again.

Struggling to find out the problem, dont want to spend $500 on a new one just for it to not charge.

FYI: yes my battery is bad, doesnt hold charge well.

appreciate any suggestions

Check out Is My Battery Bad? - 5Series.net - Forums.

Was the alternator a used one you installed? You have a bad battery? What is working? What is the voltage at the alternator?

yes it was a used one. When i checked it was about 14.5, right at start up

You need to find out if it's dropping from that proper 14.5 volts to something less when driving. I have a USB charger with a built-in voltmeter that I use just for things like this (and for checking my battery charge / condition before starting the engine). Dead cheap and hey - you need a USB charger anyway, right? ;-)

(not suggesting it's the best one, or even the best deal).

Another thing to check is that you haven't lost your engine ground strap(s). The easy way to do that is to catch the charging system misbehaving, then check for voltage between the battery negative terminal and the engine block (there should be only a small fraction of a volt - if there's more, you have a loose / corroded / missing / broken ground strap).

My problem is, the car wont charge at all. No output form the alternator. I measured straight at the alternator. It said about 1. something volts.

And im trying to figure out what exactly went wrong. Why did the alternator stop charging so fast after replacement. Is it the battery that caused it? Making it work harder, and got too hot and shorted? Because atm i cant afford doing trial and error with multiple alternator.

and 1 more thing i did was swapping regulators. The «new» one i bought only had 1 pin connector. But my old had 2. so i put the regulator from the old one onto the «new» alternator. And the old alternator was 180amps, so was the regulator. But ever partssite says its supposed to have 170amp alternator.

and more comes to mind😂 because the seller was a bit hesitant on wether it was a 150amp or a 170amp. Is it anything i can measure to find this out? Because its a chance its a 180amp regulator on a 150amp alternator.

But a couple posts ago, you said:

Color me confused.

It sounds like you may just have a garden variety bad alternator. Especially now that you put the old regulator onto the new alternator (which had a different style regulator).

yea, maybe i was unlucky with the purchase.
but i was saying the alternator was working the evening i changed it. Next morning it didnt work again, and havent since

The problem is pretty much obvious...

What happened with the original alternator was that the "brushes" (the spring-loaded blocks that make contact with the alternator's rotor) were worn down, making poor or intermittent connections.

Then you ordered a new alternator. All good, right? Nope. The connections were different, so you swapped the old regulator onto the new alternator.

Unfortunately, the brushes are part of the regulator, so you put the only bad part from the old alternator into the new one. It worked for a very short period because of the shiny new contacts on the rotor, then gave up (it'll probably work intermittently if you continued to try to use it).

So... I'd suggest your best course of action would be to order the correct voltage regulator for your car (which presumably will fit the new alternator, since the old regulator did, even if it didn't work for long). Then, with new brushes, your alternator should work again, for a long, long time (assuming you get a quality regulator, that is).

Lol. This whole thread is confusing. If the alternator is not putting out any power I would assume you'd install another alternator/voltage regulator, preferably a new one which should have been used in the first place.