Charging system problem - United Bimmer Community

**bmw325is94** · 11-25-2005, 12:54 AM

hey everybody, this is my first time posting in these forums and i was hoping that i could get some advice that could help me out.

Well here it goes, I have a 94 325is with about 150,000 miles on it now. A couple months ago the alternator died, so i replaced it along with a new battery. I was running great untill last week when it was doing the exact same thing as before. As i was driving the radio would all the sudden turn off and all i would slowly start to lose power until it just died. So i went back to advanced auto and told them what happened and the tested my alternator and battery. Both were dead so they replaced them for me for free. I put them in the next day and my car started right up. i drove it around for a lil while until to my suprise it did the same exact thing.

So this is my question, the last time it happened it was obviously not getting any power from the alternator and was only running off the battery until it killed it. So does anybody know what could possible be wrong with it. I was wondering if there was some kind of inline fuse or voltage regulator between the alternator and battery that could be causeing the problem. If somebody has any ideas please let me know. thanks

**Spieluhr** · 11-25-2005, 01:01 AM

hmm, this is really interesting.

Harry the administrator here, his call sign is 'Komodo', is having somewhat of the same issues right now.

The first thing I would check would be your alternator cooling plastic tubing. It breaks easily and might even be blocked. If your alternator is somehow overheating and blowing it will cause these problems. After that, I don't have much experience in this field.

WELCOME!

**bmw325is94** · 11-25-2005, 01:17 AM

no...the cooling duct for the alternator is fine..the only think i think it could be would be just bad alternators or something...because the last one i got never worked...my car was just running off the battery until it died and never recieved a charge...from what i could tell..i dont have a voltage meter to actually test it out

**c1apton** · 11-25-2005, 04:56 AM

Check the wiring coming from alternator if the ground is bad or weak you'll get similar results. This wiring harness is easily "chaffed" from vibration, etc. Check all the connectors - sometimes if they get hot the plastic will melt or connectors will corode or tarnish. Your regulator is in the alternator so I don't suspect that to be the problem. Some also have a fuseable link (looks like a large fuse) inline and your old alternator might have fried it. Get a small voltage tester (Radio shack, home depot - $10) and make sure you have 13+ volts at the battery when car is running.

**bmw325is94** · 11-27-2005, 07:19 PM

well i got a multi-meter and i tested the ground coming from the alternator and i got 2 ohms, so its a little weak, and i also jumped it and got it running and i only read 8 volts coming directly from the alternator. so im still lost

**DEATH2000** · 11-27-2005, 07:45 PM

Check your voltage from the battery, to operate properly it needs 13 volts as c1apton said.Also for the ground from the alternator, the 2 ohms is the resistance. Meaning the resitance of the electricy is at 2 ohms. As for 8 volts from ur alternator, i think thats not enough but im not 100% sure.

**c1apton** · 11-27-2005, 08:50 PM

I'ld be checking the warranty on your replacement alternator.After what you posted it sounds like your alternator went "south". You can verify by pulling it out and having someone like autozone or other parts stores test it for you...most will do it for free. Even replacements have bad units. Alot of rebuilders test the trade ins and replace only needed parts and don't go through them completely, some even use copper coated aluminum wiring to cut costs. Sad but true...

**bmw325is94** · 11-27-2005, 09:55 PM

Yeah...well i just replaced it at advanced auto...im sure i will be able to get another one when i got take it back...and the battery didnt have any voltage because it was all the way dead...im just afraid that if there is a problem besides the alternator that when i get the new alternator and battery it will just mess them up once again

**E36Bimmer** · 11-28-2005, 10:14 AM

The belt is attached and is not slipping, right? Also those part places often have the wrong part information on file and therefore u could have the worng alternator. There are a few different alternators used in the E36. You made sure the same amperage rating matched on the new alt right?

**bmw325is94** · 11-28-2005, 03:41 PM

well im not positive its not slipping...and its the right alternator...80 amps... the first one worked fine for 2 months....and today i just went and took out the alternator and battery...then i checked the resistance from the positve cable that hooks up to the alternator and grounded it on the chassy....it came up having 0 ohms....then i went and check resistance from the positive battery cable to the negative..again it was 0 ohms....now my question is that does that mean there is a short somewhere between the two...because with nothing conected there should be no reading at all...am i right?...in order for there to be a reading the there needs to be a complete circut

**DEATH2000** · 11-28-2005, 05:01 PM

Quote:

Originally Posted by bmw325is94

and the battery didnt have any voltage because it was all the way dead...

That could either be the cause of the alternator problem, or a result of it. I woulda had my battery changed or checked as well.

**c1apton** · 11-28-2005, 05:24 PM

You should have a "0" reading if the cables are disconnected. That's a good sign that there isn't resistance. With cables connected to alt & battery you should have 12 or 12+ volts with car off. W/car running 13+ to 15.8 is ideal. A complete circuit is what you're after.

**bmw325is94** · 11-28-2005, 06:54 PM

yeah but i am measing resistance in the circut....if there is 0 ohms that means that the circuit is complete. meaning that the positive wire is grounded somewhere. at least thats what i am asuming...somebody correct me if im wrong...so im guessing the problem is a short. although i am still totally lost

**c1apton** · 11-28-2005, 07:04 PM

[quote=bmw325is94]yeah but i am measing resistance in the circut....if there is 0 ohms that means that the circuit is complete. meaning that the positive wire is grounded somewhere. at least thats what i am asuming...somebody correct me if im wrong...so im guessing the problem is a short. although i am still totally lost[/QUOTE

You're going to get a 0 reading because the pos & neg don't connect directly to one another. One side connects to an armature in the alternator and the other to magnets that wrap around it but don't touch the armature. If they made contact that would be a dead short - similar to putting a wrench across your battery posts. When the armature spins inside the magnets it creates a field that creates voltage.

**bmw325is94** · 11-28-2005, 10:49 PM

no...i measured it with the alternator and battery off...and if there was no complete circuit there i would have not got a reading at all....but there since i got a reading of 0 ohms that means that the ciruit was completed somewhere...aka a short

**c1apton** · 11-28-2005, 11:35 PM

Quote:

Originally Posted by bmw325is94

no...i measured it with the alternator and battery off...and if there was no complete circuit there i would have not got a reading at all....but there since i got a reading of 0 ohms that means that the ciruit was completed somewhere...aka a short

Yes you have a short in your wiring. 0 ohms reading is the exact reading you'ld get if you crossed the test leads. Check your wiring harness for burns, melted connectors

**bmw325is94** · 11-28-2005, 11:57 PM

okay cool....im glad were on the same page now lol

**bmw325is94** · 11-29-2005, 06:11 PM

okay so my question now is how do i go about finding the short?