Need Help!!!! Voltage Regulator & Alternator

verde2002

verde2002

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My alternator was bad so I had it replaced. The L light was still going on and off, on at high RPM's and off once at idle. I figured it was the voltage regulator so I purchased a new one. Now the L light does not turn on in the instrument cluster but a lot of battery acid is leaking from the battery which is also new. I figured to check the voltage and at 3k rpm it is pushing over 16 volts frying the battery. I checked all connections and ground and they are all perfect. I put in the old Voltage Regulator and again it is pushing over 16 volts. Any ideas? Anyone else experienced this issue? What am I missing here?
 
The regulator is supposed to keep the voltage from the alternator in check. Are all three wires to the regulator intact and not melted together or exposed anywhere? This is a common weakness. I just installed an 80 amp alternator with internal regulator but left the old regulator on the fender with the lead for the idiot light only. It puts out 14v at 2000 rpm.
 
I will trace the wires today and see if that is the issue. Thank you for the information.
 
Do NOT run your car with the alternator-regulator putting out 16V !!!!

I fried my clock, tach, temp gauge, and load shedding relay when this happened to me last year. And trust me, replacing those parts is a pain.

As Chris wrote, installing a modern, internally-regulated alternator is a great upgrade.
 
HB Chris said:
The regulator is supposed to keep the voltage from the alternator in check. Are all three wires to the regulator intact and not melted together or exposed anywhere? This is a common weakness. I just installed an 80 amp alternator with internal regulator but left the old regulator on the fender with the lead for the idiot light only. It puts out 14v at 2000 rpm.
Click to expand...

So today I rechecked all the wires and actually replaced the wires going to the alternator and the three wires going to the voltage regulator and still I am putting out almost 17 volts. I am going tomorrow to return the new voltage regulator I bought and have it replaced, it is the only thing I can think of. I hope this works...By the way which alternator did you use with the internal regulator? Any particular part number or a specific car it comes from? Thank you.
 
I also did the replacement, used a later M30B34 Bosch unit.

16V is too much, you'll start to fry the resistance-operated devices real quick.
 
Verde,

I bought my 80 amp alternator from bnrparts on eBay. They are in the SF Valley, call them at 818-442-9082, they are very knowledgeable regarding BMWs. Think I paid $100, just in case, keep the pulley from your old alt, the new one was slightly thicker and made the PS belt run too close to the Alt. I swapped the pulleys and had plenty of clearance. I also bought my high torque small case starter from them, Bosch SR-441x and it works great. Just don't try to connect the ballast resistor lead to a terminal, it isn't needed anymore.
 
I have a 1981 BMW 633csi and was curious if the alternator on the car is the internal regulated type and if it will fit my 2800cs coupe?
 
Looking in RealOEM I don't see a Regulator for a 633, it must be internal. Compare mounting flanges, they look identical but I'm not sure.
 
I bought the new voltage regulator today and still have the same issue. A few local BMW guys have said it must have something to do with improper grounding but I have literally either replaced every wire and all the ground connections I have taken apart cleaned, sanded and put back. This is such a mystery...really makes no sense. Tomorrow I am going to the shop that sold me the alternator and they are going to take a look at it.
 
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verde2002 said:
My alternator was bad so I had it replaced. The L light was still going on and off, on at high RPM's and off once at idle. I figured it was the voltage regulator so I purchased a new one. Now the L light does not turn on in the instrument cluster but a lot of battery acid is leaking from the battery which is also new. I figured to check the voltage and at 3k rpm it is pushing over 16 volts frying the battery. I checked all connections and ground and they are all perfect. I put in the old Voltage Regulator and again it is pushing over 16 volts. Any ideas? Anyone else experienced this issue? What am I missing here?
Click to expand...


hello

where are you checking the voltage ? in which points ?

regards
 
I am convinced it's a bad alternator too considering everything else had been replaced and triple checked. I am going to the shop that rebuilt my alternator tomorrow and see if he can figure it out. He seems to think it's a bad ground too. We will see what happens.
 
Mystery solved!! I finally had a chance to install the second repleacement alternator I picked up last Friday and everything works great. Voltage will not pass 13.76 volts at any rpm. Something was apparently defective in the last alternator that I had picked up a week earlier that would not allow the voltage regulator to regulate the voltage. Because of a defective rebuilt alternator I almost blew up my battery as quite a bit of acid leaked out from every crevis, burned a voltage regulator that cost me $50 and spend hours replacing many wires I probably did not need to. The shop I bought the alternator from came highly recommended and I would hope they would have tested the altrenator they rebuilt but apparently that was not the case. Hopefully my experience will be a lesson for others and they will not go through what I did.
 
Can someone please tell me which color wires goes to which tab on the voltage regulator?? I need to connect the old blue wire to the new wiring I did so I can have the dummy L light work again in my dash. Thank you.
 
Regulator wiring

My wiring diagram is a copy but here goes:

Brown = D-
Black = DF
Blue = D+ (this also goes from regulator to the idiot light)
 
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