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Old 09-24-2014, 01:29 AM   #1
firehawk
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Join Date: Feb 2014
Location: OC, CA
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My Ride: '03 325CI 5-Speed
Voltage Regulator went bad. Too much voltage burned out headlight & brake light

Even though I don't consider myself an expert or anything, I believe my voltage regulator has gone bad. I do have a question for you guys, but first let me tell you what happened...

I was driving down the highway when the battery light turned on. Since the car was in gear and moving the triangle light and brake light lit up as well. The car did not bog or anything, but I pulled right over and scanned for codes. No codes showed up. I unplugged the battery for a few minutes to see if that did anything, which it did not.

Next I ran a battery voltage test with the built-in test on the dash. Went to number 19 and unlocked everything, then went to number 9 for the battery test. With the engine off, the battery was at about 13-ish. As soon as I turned the motor on and revved the motor a tiny bit the voltage jumped up to 16-17-ish. When I revved to around 2k the voltage hit 18-ish and the left daytime running light and rear right tail light went poof.

After some Googling around, it seems the voltage regulator has gone bad. My question is can I just buy JUST the voltage regulator, or do I need to replace the alternator too? I think the alternator is working fine as the voltage was steadily increasing as I was softly revving it. I know I need to pull out the alternator to manually see if the voltage regulator is rectangular or oval. RealOEM states I should have the rectangular one.

Any advice on how I should approach this? Im pretty far from home in a hotel at the moment.

Last edited by firehawk; 09-24-2014 at 01:32 AM.
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Old 09-24-2014, 01:42 AM   #2
Benny Minn
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Interesting....I've only seen the opposite happen with that failure. You can buy just the voltage regulator separate from the alternator. And you are right to visually verify which style you need. This can be done without removing the alternator too. That sucks that you're stranded with it, though. I hope your hotel is near an auto parts store.
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Old 09-24-2014, 01:59 AM   #3
firehawk
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Quote:
Originally Posted by Benny Minn View Post
Interesting....I've only seen the opposite happen with that failure. You can buy just the voltage regulator separate from the alternator. And you are right to visually verify which style you need. This can be done without removing the alternator too. That sucks that you're stranded with it, though. I hope your hotel is near an auto parts store.
Thanks for responding so quickly. It would be interesting to see if any other members have any experience with high voltage as opposed to low voltage (which im sure is more common).

Yea it sucks since I'm so far from home. The parking garage I'm in does not allow working on cars lol. The car starts and seems to run fine (minus the lights on the dash demanding my attention), so I could probably quickly move it to a Pep Boys parking lot, but I'm wondering if too much voltage like this could possibly do so much damage that I'm better off getting towed to a parking lot where I can do the work myself or paying the premium for bringing it to a local BMW indy. Im kinda concerned that after driving it to my hotel, 2 bulbs have burned out already. Im not sure what else is "next".
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Old 09-24-2014, 02:06 AM   #4
Benny Minn
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I've read a lot about how sensitive these cars are to voltage. I would not risk driving it any further. Find the nearest store with the right VR and tow it there. You can pick up new bulbs at the same time. I don't think the indy needs to be involved with this unless you're under tight time constraints.
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Old 09-24-2014, 06:29 AM   #5
firehawk
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Quote:
Originally Posted by Benny Minn View Post
I've read a lot about how sensitive these cars are to voltage. I would not risk driving it any further. Find the nearest store with the right VR and tow it there. You can pick up new bulbs at the same time. I don't think the indy needs to be involved with this unless you're under tight time constraints.
Thanks for the input. Since the voltage was increasing as I revved it, I'm guessing the alternator is fine and its just the voltage regulator that went bad. I'll update this thread once it's fixed but I'm definitely interested in hearing what anyone else thinks I should check out! Thanks
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Old 09-24-2014, 07:39 AM   #6
markusmarkus
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The VR is definitely shot. The issue now is which brand of alternator is in the car! BMW sourced alternators from 2 companies: BOSCH and Valeo. The VR on BOSCH alternators can be repaired. I bought a VR from FCPEuro for about $45. Easy install. Valeo alternators have to be replaced as they can't be repaired.

How to tell which alternator is in your car? Remove the air filter housing. Use a flashlight and a small mirror to read the label on the back of the alternator. If you're lucky it'll read "Bosch."

No, you can't swap a Valeo for a Bosch! The connectors are different - square vs oval.


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Old 09-24-2014, 07:40 AM   #7
markusmarkus
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My post should have said, "The VR on the Bosch can be replaced."


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Old 09-24-2014, 08:08 AM   #8
firehawk
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Quote:
Originally Posted by markusmarkus View Post
The VR is definitely shot. The issue now is which brand of alternator is in the car! BMW sourced alternators from 2 companies: BOSCH and Valeo. The VR on BOSCH alternators can be repaired. I bought a VR from FCPEuro for about $45. Easy install. Valeo alternators have to be replaced as they can't be repaired.

How to tell which alternator is in your car? Remove the air filter housing. Use a flashlight and a small mirror to read the label on the back of the alternator. If you're lucky it'll read "Bosch."

No, you can't swap a Valeo for a Bosch! The connectors are different - square vs oval.


Sent from BimmerApp mobile app


Quote:
Originally Posted by markusmarkus View Post
My post should have said, "The VR on the Bosch can be replaced."


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If it's Valeo then I need to buy the entire alternator + regulator as a unit for like $200? And just to be precise, if it's Bosch then I can buy just the regulator for $50? Ohhh, pray for me! I'd much rather spend that $150 on anything else, haha!
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Old 09-24-2014, 11:02 AM   #9
cvx5832
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Quote:
Originally Posted by firehawk View Post
Even though I don't consider myself an expert or anything, I believe my voltage regulator has gone bad. I do have a question for you guys, but first let me tell you what happened...

I was driving down the highway when the battery light turned on. Since the car was in gear and moving the triangle light and brake light lit up as well. The car did not bog or anything, but I pulled right over and scanned for codes. No codes showed up. I unplugged the battery for a few minutes to see if that did anything, which it did not.

Next I ran a battery voltage test with the built-in test on the dash. Went to number 19 and unlocked everything, then went to number 9 for the battery test. With the engine off, the battery was at about 13-ish. As soon as I turned the motor on and revved the motor a tiny bit the voltage jumped up to 16-17-ish. When I revved to around 2k the voltage hit 18-ish and the left daytime running light and rear right tail light went poof.

After some Googling around, it seems the voltage regulator has gone bad. My question is can I just buy JUST the voltage regulator, or do I need to replace the alternator too? I think the alternator is working fine as the voltage was steadily increasing as I was softly revving it. I know I need to pull out the alternator to manually see if the voltage regulator is rectangular or oval. RealOEM states I should have the rectangular one.

Any advice on how I should approach this? Im pretty far from home in a hotel at the moment.
If your "far" means you took a road trip to the Bay Area, let me know if you want a roof and some tools to get the job done.

If it means you went to Vegas, drop a coin in the slot and see if you can go home in a Ferrari!!
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Old 09-24-2014, 11:43 AM   #10
firehawk
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Quote:
Originally Posted by cvx5832 View Post
If your "far" means you took a road trip to the Bay Area, let me know if you want a roof and some tools to get the job done.

If it means you went to Vegas, drop a coin in the slot and see if you can go home in a Ferrari!!
Ahh damn, I'm in San Diego! Wish I was in San Fran though after your generous offer!

Just called 2 indy shops and 1 quoted me $750 while the other quoted $500. Ha at those prices!
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Old 09-24-2014, 09:19 PM   #11
Benny Minn
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Quote:
Originally Posted by markusmarkus View Post
The VR is definitely shot. The issue now is which brand of alternator is in the car! BMW sourced alternators from 2 companies: BOSCH and Valeo. The VR on BOSCH alternators can be repaired. I bought a VR from FCPEuro for about $45. Easy install. Valeo alternators have to be replaced as they can't be repaired.

How to tell which alternator is in your car? Remove the air filter housing. Use a flashlight and a small mirror to read the label on the back of the alternator. If you're lucky it'll read "Bosch."

No, you can't swap a Valeo for a Bosch! The connectors are different - square vs oval.


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I've purchased both Valeo and Bosch VRs separately. Both can be replaced without swapping the whole alternator.
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Old 09-26-2014, 03:26 AM   #12
firehawk
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Quick update. My battery is now completely dead but I have a new voltage regulator being overnighted to my house and I'll be calling AAA for a tow home in the morning. Thank god I opted for AAA Plus a few months ago... that 100 mile tow package is really coming in clutch for me, haha.

I'll update this thread once it's fixed so people Googling around get some answers. I took off the air filter box and could visually see I had the rectangle style connector and with a mirror could see Bosch printed on the back.

Hopefully I'll be back on the road tomorrow! I've been following mango's guides for vacuum and cooling, but stupidly did not replace this fricken voltage regulator and now its bit me in the ass

Last edited by firehawk; 09-26-2014 at 03:27 AM. Reason: grammar nazi spelling mistake
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Old 09-29-2014, 09:20 PM   #13
firehawk
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Update:

Voltage Regulator came in the mail today, installed it in about 1hr, and I'm back on the road! Voltage seems to be holding steady right around the 14v mark with the motor on.... I Haven't seen it go above 14.1. With the car off it's around 12.7v. I don't consider myself a mechanic whatsoever so this is an easy DIY.

I did purchase a new battery for $160 as well, so my total cost is $220 ($60 for VR + shipping + $160 for battery). After reading mango's guides, the first thing he said to replace is the battery so I got caught up and purchased that. Next on my list is the final stage resistor. I bought my E46 earlier this year with 117k miles on it, now it has 124k. Here's my full list of everything I've done thus far.

-Complete Cooling System Overhaul (thermostat, water pump, radiator, expansion tank, coolant level sensor, and every single hose)
-New Cold Weather CCV Kit (even though I live in CA)
-Fuel Filter
-New pulleys + belts
-Oil Filter Housing Gasket
-Vanos seal (Beisan systems)
-Valve Cover Gasket
-New DISA Valve
-New MAF
-Spark Plug Boots
-Differential Bushing (powerflex) + Swapped Diff Fluid
-Manual Transmission Fluid Change
-Guibo + Center Support Bearing
-Rear Parking Shoes + Rear Rotors (paid indy shop for this)
-NOW New Battery + New Voltage Regulator

Next things I'm gonna do are Final Stage Resistor, Ignition Switch and front Control Arm Bushings (Powerflex), and Fuel Pump. I've been doing all this preventative maintenance so I don't get stranded, but the voltage regulator got me so I suggest replacing yours!

Last edited by firehawk; 09-29-2014 at 09:53 PM.
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Old 09-30-2014, 03:41 AM   #14
BaliDawg
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Hey, good job diagnosing and fixing your VR problem. This forum is an awesome support system for an E46Fan in trouble.

I have a spare 2004 325Ci motor in my garage if you need any good used parts. Just PM me. I live in the IE but work in OC.
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Old 09-30-2014, 11:29 AM   #15
Benny Minn
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Hey, firehawk, glad you got it worked out. It sounds like you're on the right track with all other maintenance as well. Rock on!
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Old 09-16-2016, 11:15 AM   #16
Mr.fixitautorepair
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My voltage regulator went bad on my 2000 bmw 328ci which caused the battery terminals and whole battery to heat up very hot due to overcharging. It literally melted part or my postive battery post to melt off. I had a spare battery in my trunk that i swapped in on the side of the road.when i went to hook up the spare battery it sparked really bad and heated up like it had a dead short so i unhooked the square connector and tried hooking my spare up. This time i hooked the battery up with no arc or heating up. Drove my car home and didn't even have a battery light on with no problems at all with the square connection disconnected. I guess the regulator was causing a dead short. I've been driving the car with the square connector disconnected with no problems while I'm waiting for the new voltage regulator to come in the mail.
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